Medical Microbiology Class 1,2,3 PDF

Medical Microbiology for Pharmacy  Outline Definition: Microbiology, Microorganisms Scope of Microbiology Importance of Microorganisms Brief History of Microbiology Taxonomy & classification of microorganisms Morphology, growth and nutrition of bacteria Mutation and bacte...

Medical Microbiology for Pharmacy  Outline Definition: Microbiology, Microorganisms Scope of Microbiology Importance of Microorganisms Brief History of Microbiology Taxonomy & classification of microorganisms Morphology, growth and nutrition of bacteria Mutation and bacterial gene transfer Mechanisms  Introductio n Definition Microbiology :- a subject which deals with living organisms that are individually too small to be seen with the naked eye Medical microbiology:- deals with microorganism that cause infectious diseases and the body’s defenses against disease  Introduction Etiology(causative cont.… agent) Disease In medical manifestation microbiolog Mode of y one should transmission have a Laboratory clear diagnosis understand Treatment ing of: Prevention and control of infectious disease  Branches of medical microbiology Virology -studies about viruses Bacteriology – which deals with bacteria Mycology- which deals with fungi Parasitology- which deals with parasite Protozoology – which deals with Protozoa Immunology- body’s defenses against pathogens  Viruses smallest infectious particles(18 to 600 nm in diameter) not be seen with a light microscope. typically contain either DNA or RNA but not both But recently discovered Mimivirus contains both RNA and DNA. The genetic material are enclosed in a protein shell with or without a lipid membrane coat. Viruses are true parasites, requiring host cells for replication. More than 2000 species of viruses have been described,  Bacteria prokaryotic organism unicellular organism Contain rigid cell wall except mycoplasma Contain both DNA and RNA Most grow in artificial media Replication is by binary fission Contain rigid cell wall except mycoplasma  Fungi Eukaryotic organisms Exist as either in a unicellular form yeast that can replicate asexually or in a filamentous form mold that can replicate asexually and sexually. Dimorphic(both yeast(37c) and mold(>37) depending tempreture) fungi e.g Histoplasma, Blastomyces, and Coccidioides  Parasites Eukaryotic, some are unicellular and others are multicellular. They range in size from tiny protozoa as small as 4 to 5 µm in diameter (the size of some bacteria) to tapeworms that can measure up to 10 meters in length and arthropods (bugs).  Increasing complexity viruses → bacteria → fungi → parasites  Historical Background Man kind has always been affected by diseases which were originally believed to be visitations by the Gods and meant to punish evil doers. Hippocratus, father of medicine, observed that ill health resulted due to changes in air, winds, water, climate, food, nature of soil and habits of Fracastorius people. (1500 G.C.) proposed that the agents of communicable disease were living germs, that could be transmitted by direct contact with humans and animals, and indirectly by objects ; but no proof because of lacking The first person to see bacteria was Antonie Van Leeuwenhoek (1632-1723 G.C), father of Microbiology by constricting his own microscope.  He was the first who properly Observed described the “animalcules” different shapes using simple of bacteria. microscope with one lens. where did they Question originate? raised There are two major theories Theory of about the origin Abiogenesis of microorganism Theory of s. Biogenesis  Spontaneous generation(Theory of Abiogenesis) Aristotle (384-322 BC): The founder of a theory spontaneous generation States that living things originated “spontaneously” from non-living things Fishes from dried ponds Fleas from putrid matter Mice from dirty hay Maggots from meat etc.  Francesco Redi (1626-1697): He is the scientist who first tried to set an experiment to disprove spontaneous generation  Utilized jars containing meat. Some were covered, some were not  Maggots appeared in uncovered jars  Results not accepted for microscopic organisms  The controversy on spontaneous generation took 200 years In 1859 Louis pasture disproved the theory of abiogenesis once and for all Louis Pasteur experiment  The Germ Theory of diseases Is the idea that diseases may be caused by microscopic organisms The most important contribution to medical science and practice, ever Corner stone of: Epidemiology Development of antimicrobial drugs Development of vaccine Hygienic practice Public health  The Germ Theory of diseases cont.. Germ theory of diseases, which states that a specific disease is caused by a specific type of microorganism developed by Robert Pasture. Koch, in 1876 established an experimental procedure to prove the germ theory of disease. The scientific procedure is known as Koch’s Postulate.  Koch’s Postulate A Micro-organism can be accepted as a causative agent of an infectious disease only if the following conditions are satisfied. 1. Microorganism must be associated with the disease 2. Microorganism must be isolated in pure culture 3. Isolated microorganisms must produce disease when inoculated in to human or  Exceptions to Koch’s postulate Many healthy people carry pathogens but do not exhibit symptoms of the disease. Some microbes can not grow in vitro (in the laboratory) in artificial media. Eg. Treponema pallidum. Many pathogens are species specific. Eg. Brucella abortus cause abortion in animals but not in humans. Certain diseases develop only when an opportunistic pathogen invades immuno- compromised host.  Major achievements of Robert Koch  Discovery and use of solid medium in bacteriology  Discovery of causative agents of tuberculosis and cholera  Koch’s postulate Vaccination: In 1798, Edward Jenner demonstrated that inoculation with cowpox material provides human with immunity to small pox. About 1800, Pasteur discovered that avirulent bacteria could be used as a vaccine for cholera; he coined the word vaccine. Antibiotics: Alexander Fleming observed that the mould (fungus) penicillium inhibited the growth of bacterial culture. He named the active ingredient penicillin (1928). Classification of Microorganisms Characteristic Eukaryote Prokaryote Major groups Algae, fungi, protozoa, Bacteria plants, animals Size (approximate) >5 μm 0.5-3.0 μm Nuclear Structures Nucleus Classic membrane No nuclear membrane Chromosomes Strands of DNA Diploid genome Single, circular DNA Haploid genome Cytoplasmic Structures Mitochondria Present Absent Golgi bodies Present Absent Endoplasmic Present Absent reticulum Ribosomes 80S (60S +40S) 70S (50S +30S) (sedimentation coefficient) Cytoplasmic Contains sterols Does not contain sterols membrane Cell wall Present for fungi; otherwise Is a complex structure absent containing protein, lipids, and peptidoglycans Reproduction Sexual and asexual Asexual (binary fission) Movement Complex flagellum, if present Simple flagellum, if present Nomenclature and Bacterial Cell Structure  Nomenclature In binomial system, each organism is given two names The first is the genus or genera (plural) and the second is the species To express genus capitalize the fist letter of the word and underline or italicize it for example Esherchia. To express genus and species together, capitalize the first letter of the genus name (and then underline or italicize the entire name- for example Eschelchia coli. The genes can be abbreviated as E.coli  Most species name tell as some thing about the organism – Its appearances – Its source – A characteristic property – Scientists discover, described or was connected with it Escherich coli – name for microbiologist Theodor Escherichia and its usual habitat, the colon Staphylococcus aureus– characteristic way its cells aggregate to resemble a bunch of grapes (staphyle- cluster) and its yellow colonies(aureus- golden)  Morphology of bacteria Shape and size – ranging(0.2 µm to 10µm ) There are three basic shapes Spherical or coccoid/cocci- (singular – coccus) Rods or bacilli (singular - bacillus) Spirals or spirilla (Singular - Spirillum)  Structure of Bacteria Arrangement: The cells of cocci may be found in various arrangements depending on the species and the way they divide. E.g. Staphylococci- Cocci in cluster Streptococci – Cocci in chain Diplococci- Pairs of cocci Micrococcus:-Cocci occurring single Bacilli (rods) may be short or long, thick or thin, pointed or with blunt ends. Some rods resemble cocci and are often called coccobalilli because they are very short small bacilli. Some are coma shaped e.g. V.cholara  Bacterial cell structure Bacterial structure is considered at three levels 1. Cell envelope: Capsule, cell wall and cell membrane 2. Cellular element enclosed with in the cell envelope: Ribosome, nuclear material, and cytoplasmic granules 3. Cellular element external to the cell envelope (appendages) : Flagellum, Pilus Bacterial structures and function  Mycobacteria mycoplasmas Cell wall(Gram positive and Cytoplasmic inclusions negative cell wall Cytoplasmic membrane (Plasma Nuclear material membrane) Plasmid(Virulence plasmids and Resistance Cytoplasm (R) plasmids) Flagellum(Flagella) Capsule and slim layer Pilli and Fimbriae Ribosomes Bacterial spores Bacterial cell  Types of cell wall I. Gram positive cell wall of bacteria Has two layers Peptidoglycan (PG) cross linked with teichoic acid) The PG layers is much thicker than Gram negative bacteria and i.e. 15 – 50 nm thick  Teichoic acid These polymers of glycerol phosphate or ribitol phosphate are located in the outer layer of the PG cell wall Function of Teichoic acid  Used to bind (keep) Mg+2 concentration in the cell wall  Used to activate autolytic enzyme (enzymes which are secreted by bacteria usually when it dies  II. Gram negative Cell wall of bacteria Is some what complex than Gram positive bacterial cell wall Has thin peptidoglycan layer (3 – 8nm) Has high lipid content (lipopolysaccharied) in the outer membrane Has periplasmic space  (a) (b) Fig. Gram-Positive (a) and Gram negative (b) cell wall of bacteria  Capsule Capsule Capsules are often regarded and slim as portion of the cell layer envelope Mediate adherence Capsular constituents vary among the different species Protect bacterial cells of prokaryotes from engulfment Many bacteria have slimy Protect cells layers, consisting of from drying polysaccharides only; others Become have proteins within the reserves of carbohydrate polysaccharide capsule for subsequent metabolism  Cytoplasmic membrane (Plasma membrane) It is the actual barrier between the interior and exterior of the bacteria cell The cytoplasmic membrane exhibits a well- defined selective permeability, excretion of enzyme, and biosynthesis of cell well and other proteins The bacterial transport system and the principal energy system (oxidative phosphophorylation) are located in the  Cytoplasm Viscous watery solution of soft gel, containing a variety organic and inorganic solutes and numerous small granule called ribosomes The cytoplasm consists of water, enzymes, oxygen, waste products, essential nutrients, proteins, carbohydrates, lipids and a complex mixture of all the materials required by the cell for its metabolic functions  Ribosomes  Cytoplamic particles, which are the sites of protein synthesis Cytoplasmic inclusions Are distinct granules that may occupy a substantial part of the cytoplasm Are usually reserve materials of some sort. For example, carbon and energy reserves may be stored as glycogen (a polymer of glucose) polybetahydroxybutyric acid (a type of fat) granules Polyphosphate inclusions are reserves of PO4  Nuclear material The nucleoid consists of one long double- stranded circular DNA molecule (chromosome) The chromosome serves as the control center of the bacterial cell, carries the genetic information needed for producing several thousand enzymes and other proteins It is not surrounded by a nuclear membrane  Plasmids Extrachromosomal genetic materials Circular double strand DNA molecules present in the cytoplasm of bacteria, capable of autonomous replication The following plasmid types are medically relevant:  Virulence plasmids: Carry determinants of bacterial virulence (virulence genes), e.g., enterotoxin genes or hemolysin genes  Resistance (R) plasmids: Carry genetic information bearing on resistance to antibacterial agents  R plasmids may carry several R genes at once Flagellum It is the organ of locomotion in bacterial cell and consists of filament Is free on the surface of bacterial cell It is composed of protein named as flagellin  Flagellum … Cont’d Flagellar arrangements 1. Atrichous: Bacteria with no flagellum: Eg. All cocci 2. Monotrichous: Bacteria with single polar flagellum: Eg. V.cholara 3. Lophotrichous: Bacteria with bunch of flagella at one pole: Eg. Pseudomonas flouresense 4. Amphitrichous: Bacteria with flagella at both poles: Eg. Alcaligenes faecales 5. Peritrichous: Bacteria with flagella all over their surface: Eg. S.typhi  Pili (Fimbriae) Interchangeable terms used to designate short, hair-like structures (finer filaments) on the surfaces of prokaryotic cells Are extruding from the cytoplasmic membrane Are shorter and stiffer than flagella, and slightly smaller in diameter Like flagella, they are composed of protein Two functional types of pili may occur independently or together on some cell I. Common pili – Help for attachment of bacteria to epithelial cell II. Sex pili – Occur less commonly – Appear to be specifically involved in bacterial conjugation, i.e transfer of genetic material (DNA) from one bacterium to another  Bacterial spores Under conditions of limited supply of nutrition, vegetative forms of certain bacteria form highly resistant and dehydrated forms, which are called spores These spors are capable of survival under adverse conditions such as heat, drying, freezing, radiation, and actions of toxic chemicals Spores are usually smooth walled and avoid, in some species it is spherical Fig. Different arrangements of spores in the bacteria  Bacterial growth Bacteria divide by binary fission. When a bacterial cell reaches a certain size, it divides to form two daughter cells. Nuclear division precedes cell division and, therefore, in a growing population, many cell carrying two nuclear bodies can be found. The interval of time between two cell division, or the time required for a bacterium to give rise to two daughter cells under optimum conditions is called Generation time or population doubling time The generation time of bacteria ranges from as little  Bacterial growth curve The growth cycle of bacteria has four major phases. If a small number of bacteria are inoculated into a liquid nutrient medium and the bacteria are counted at frequent interval, the typical phase of a standard growth curve can be demonstrated. 1. The Lag Phase this phase is of short duration in which bacteria adapt themselves to new environment in such away that the bacterial machinery brings itself in conformity with the nutrition available. It is the preparation time for reproduction No increase in cell number occurs, however, vigorous metabolic activity occurs.  Bacterial growth curve 2. The log, logarithmic, or exponential phase During this phase, the population growth exponentially At the log phase the following events occur Exhaustion of nutrients Accumulation of toxic metabolic end products Rise in cell density  Bacterial growth curve … Cont’d 3. Stationary Phase Occur when nutrients depletion or toxic products cause growth to slow The number of viable cell remain constant There is almost a balance between the bacterial reproduction and bacterial death 4. The death/decline phase Due to depletion of nutrients and accumulation of toxic end products the number of bacteria dying is much more than those dividing and hence there is gradual decline in the total number of organism. Fig. Bacterial growth curve  Nutrition For optimal growth and multiplication, bacteria requires nutrients, such as water, energy, carbon, nitrogen and some inorganic salts Bacteria also require various environmental factors for growth in optimum concentration. These include Oxygen/Carbon dioxide, pH, temperature All bacteria need some form of the element Carbon, H, O2, S, P, and N for growth Special elements such as K, Ca, Fe, Mn, Mg, Co, Cu, Zn are needed by certain bacteria  1. Nutrient requirement Depending on their nutritional requirement bacteria can be classified Autotrophs: - are free-living, non-pathogenic bacteria, most of which can use carbon dioxide as their carbon source. The energy needed for their metabolism can be obtained from (a) Sunlight-photoautotrophs and (b) inorganic compounds by oxidation- chemoautotrophs Heterotrophs are generally parasitic bacteria which require more complex organic compounds than carbon dioxide as their source of carbon and energy, e.g. sugar  2. Temperature requirement Most pathogenic bacteria grow best at an optimum temperature of 370C Based on temperature requirement, microorganisms can be broadly classified into Psycrophilic- are those bacteria, which grow in the range of -5 to 200C These bacteria include those which cause spoilages of food at refrigeration temperature (2- 8oc)  Mesophilic- are those bacteria, which grow at 20-450C and show optimum growth at 37oC – all medically important bacteria (pathogenic bacteria) belong to this group Thermophilic – are those organisms which prefer high temperature (50-800C) – May cause spoilage of under processed canned food  3. Oxygen requirement The need of oxygen for particular bacterium reflects its mechanism to meet the requirement of energy On the basis of this requirement, bacteria have been divided in to: Obligate Anaerobes-these grow only in the environment devoid of oxygen e.g. clostridium Facultative aerobes- these can grow under both aerobic and anaerobic conditions, e.g. enterobacteriaceae  Obligate aerobes- these cannot grow unless oxygen is present in the medium, e.g. pseudomonas Microaerophilic- these organisms lower concentration of oxygen than are present in the air(10%) e.g. campylobacter Carboxyphilic – live and grow best in atmosphere which contain increased amount of CO2 (5-10%).e.g Neisseria meningitidis, Neisseria gonorrheae Aerotolerant anaerobes – These bacteria oxidize nutrient substrates without using elemental oxygen Unlike obligate anaerobes, they can tolerate the presence of oxygen  4. pH requirement Most pathogenic bacteria require a pH of 7.2-7.6 for their optimal growth. Based on pH requirement bacteria can be classified as Neutrophilic:- bacteria grow best at neutral pH (pH=7) – Most pathogenic micro-organism best grow at neutral pH (pH=7) Acidophilic – Bacterial grow best at acidic pH (pH7) – E.g. Vibrio cholerae grow at a pH of 8.6  Exchange of genetic information Involve a unilateral transfer of genetic information from a donor cell to a receptor cell The transfer of genetic information can occur by either of the three methods: Transformation Transduction Conjugation Transformation A process by which a bacterium acquire DNA fragments or genes from surroundings. Usually this occurs in microbial culture. Fig. Transformation process in bacteria Transduction is a method of gene transfer in which a virus (phage) acts as a vehicle for carrying DNA from a donor bacterium to recipient bacterium. Fig. Transduction of a chromosomal DNA sequence (a) and a plasmid (b). Conjugation A process where by DNA is transferred from one bacterium to another by cell to cell physical contact Plasmids are the genetic elements most frequently transferred by conjugation.A. Conjugation: connection between two bacterial cells by means of sex pili. This initial step alone does not necessarily always lead to effective conjugation. B. Effective conjugation: formation of a specific conjugal bridge between donor cell and receptor cell. C. Plasmid mobilization and transfer: an endonuclease cleaves one strand of the circular DNA double helix at a specific point (b). The single strand with the “leader region” enters the receptor cell. D. Synthesis: the double-stranded structure of both the transferred single strand and the remaining DNA strand is restored by means of complementary DNA synthesis. Fig. Transfer/replication process of a NB: Conjugationconjugative is seen frequently in Gram-negative rods plasmid. (Enterobacteriaceae)  IMMUNOLOGY 01/27/2025 Firayad A 67 01/27/2025 Firayad A 68  Outline Innate and adaptive immunity Humoral and cell mediated immune response Hypersensitivity reactions Immunization 01/27/2025 Firayad A 69  An Overview of the Immune System 01/27/2025 Firayad A 70  Immunology Is study of immune system or immunity Is the study of how the body protects itself against infectious diseases caused by microorganisms, such as bacteria, viruses, protozoa, and fungi, and helminth worms It is all about how you can manipulate disease or protect against disease The overall ability of the host to fight the disease causing pathogens 01/27/2025 Firayad A 71  Immune system It is a system that the body builds a defense against that specific antigen/against infections. Cells and molecules involved in such protection The response to a foreign agent is known as the immune response  Immunity(State of protection from infectious diseases) is the capability of multicellular organisms to resist harmful microorganisms. Immunity involves both specific and nonspecific components The nonspecific components act as barriers or eliminators of a wide range of pathogens irrespective of their antigenic make-up. 01/27/2025 Firayad A 72  The immune system Immune System Innate Adaptive (Nonspecif (Specific) ic) Cellular Humoral Cell- Humoral Componen Componen Mediated (Ab) ts ts 01/27/2025 Firayad A 73  The adaptive immune response attack non-self The two type of pathogens but can sometimes make errors immunity and attack itself Innate immunity Adaptive immunity -Non specific -No memory cell -Specific -Rapid -Acquired after response(acting) birth(passively or -Present at birth actively)  Everyone is born -Has a memory with innate (or -Slow acting(but the natural) immunity, second response is a type of general rapid) protection 01/27/2025 Firayad A 74  Adaptive immunity Naturally acquired Artificially acquired immunity immunity  Passive immunity  Passive immunity  Immunity antibody  Performed Antibody given from mother to fetus via placenta or to by ejection infant via mother milk  Active immunity  Active immunity  Antigens introduced to  Antigens enter the the body in the form of body and the body vaccine and the body produced Antibody produced Antibody naturally and naturally and specialized specialized lymphocytes cell lymphocytes cell 01/27/2025 Firayad A 75  Cell of immune system 01/27/2025 Firayad A 76  Cell of immune system 01/27/2025 Firayad A 77  Physical barrier(Anatomical Innate Adaptive barriers) Immunit Immunity  Mechanical factors y (Skin, Mucus Membrane) Humoral  Biological factors  Physiological (Normal Florabarriers in skin) B-cell  Acid in the (B-cell stomach(1)vagina(4-5)  Saliva, Bile differentiate  Tear and Sweat The two d in to  Cellular components Component plasma  Neutrophils s cell(Ab) and  Monocytes and memory cell) macrophages Cell  NK cells mediated  Eosinophils Th(CD4)  Humoral components Tc(CD8)  Complément Memory T-  Cytokines  Inflammation It is defense mechanism Inflammation is the immune system's response to harmful stimuli, such as Pathogens damaged cells toxic compounds, or irradiation and acts by removing injurious stimuli and initiating the healing process 01/27/2025 Firayad A 79  Inflammation Overall non-specific reaction of body to injury or invasion – starts immediately with infection or trauma Can be acute (short duration) or become chronic (prolonged duration) Has 4 cardinal signs: heat, pain, redness, loss of function resulting from: 01/27/2025 Firayad A 80 01/27/2025 Firayad A 81  COMPLEMENT SYSTEM The Complement is a multi-component system composed of plasma proteins capable of destroying pathogenic organisms and other cells that express foreign antigen. Functions of Complement Direct Lysis of bacteria, some viruses and cells. Opsonization and enhanced phagocytosis. Triggers cellular functions that contribute to inflammation. Facilitates removal of immune complexes 01/27/2025 Firayad A 82 Complement Activation Three major pathways lead to complement activation 1. Classical pathway-initiated by antibody binding to antigens on pathogens. 2. Alternate pathway - initiated by direct interaction of complement with pathogen surfaces. 3. Lectin pathway -initiated by binding to mannose residues found on certain bacterial strains. All leading to the activation of the membrane attack (lytic) pathway 01/27/2025 Firayad A 83 01/27/2025 Firayad A 84 01/27/2025 Firayad A 85 01/27/2025 Firayad A 86 Determinants Recognized by the Innate Immune Syst The innate immune system functions by recognizing highly conserved sets of molecules PAMPs – Pathogen Associated Molecular Patterns Are structural molecules on the surface of microbes or secreted; that are recognized by the host innate immune molecules. PRRs – Pattern Recognition Receptors Are molecules on the cells and or molecules of the immune system that are capable of recognizing foreign substances. 01/27/2025 Firayad A 87 Example toll like receptors (TLRs) Determinants Recognized by the innate immune system Adaptive immune system –discrete determinates React with a specific pathogen Innate immune system- broad molecular patterns React with a variety of pathogens 01/27/2025 Firayad A 88  Adaptive immune system Capable of recognizing and selectively eliminating specific foreign microorganisms and molecules(i.e., foreign antigens). Unlike innate immune responses, adaptive immune responses are reactions to specific antigenic challenges Different populations of lymphocytes and their products are the major actors together with accessory cells – Antigen presenting cells (APCs) 01/27/2025 Firayad A 89  Features of adaptive Immune Responses Specificity specific for distinct antigen. Diversity- total number of antigenic specificities of the lymphocytes in an individual is extremely large. estimated mammalian immune system can discriminate 109 to 1011 distinct antigenic. Non-reactivity to self Ability to recognize, respond and eliminate many non-self antigens while not reacting harmfully to 01/27/2025 self antigens. This immunological Firayad A 90 Features of Adaptive immune system … Memory- Exposure of the immune system to foreign antigen enhances its ability to respond again to that antigen. Specialization – humoral immunity and cell mediated immunity extra cellular & intra cellular Self –limitation- All normal immune responses returning the immune system to its resting or basal state with time after antigen stimulations, process called homeostasis. 01/27/2025 Firayad A 91 01/27/2025 Firayad A 92  ANTIGENS AND ANTIBODY 01/27/2025 Firayad A 93  Definitions Antigen (Ag) : is substance which when introduced parentally into the body stimulates the production of an antibody with which it reacts specifically and in an observable manner. Antibody (Ab): – A specific protein which is produced in response to an immunogen and which reacts with an antigen 01/27/2025 Firayad A 94  Immunogenicity Versus Antigenicity Immunogenicity is the ability of a molecule/microbe or cell to be recognized by hosts immune cells and elicit an immune response. Antigenicity is the ability of a molecule to bind/react with the products of an immune response (antibodies or lymphocytes) Not all antigens are immunogens while all immunogens are antigens. Haptens, are antigenic but incapable, by themselves, of inducing a specific immune response. In other words, they lack immunogenicity 01/27/2025 Firayad A 95  Classification of Antigen Basis for classification: Complete and Incomplete According to source/origin of Ag According to whether need the help of T cells when B cells produce Ab Based on chemical nature 01/27/2025 Firayad A 96  Classification of Antigen Complete and Incomplete  Incomplete antigens: A substance that is non- immunogenic but which can react with the products of a specific immune response.  Complete antigens: Are usually proteins or porteinous in nature, large in molecular size and are capable of stimulating an immune response by them selves  According to source/origin of Ag  Exogenous antigens: Are antigens that have entered the body from the outside, for example by inhalation, ingestion, or injection.  Endogenous antigens: Are 01/27/2025 Firayad Aantigens that have been 97  Classification of Antigen Based on chemical nature antigens classified into: Protein antigens:- pure proteins or glycoproteins or lipoproteins: are usually very good immunogens Polysaccharide antigens:- Pure polysaccharides and lipopolysaccharides are good immunogens. Nucleic acid antigens:- Nucleic acids are usually poorly immunogenic. Lipid antigens:- In general lipids are non- immunogenic, although they may be haptens. 01/27/2025 Firayad A 98  Classification of Antigen cont… T-dependent- antigens: Do not directly stimulate the production of antibody without the help of T cells. Proteins are T-dependent antigens. T-independent antigens: Can directly stimulate the B cells to produce antibody without the requirement for T cell help. Examples: lipopolysaccharide, Flagella 01/27/2025 Firayad A 99  Epitopes Immune cells do not interact with, or recognize, an entire immunogen molecule. Epitopes or antigenic determinants are the immunologically active regions of an immunogen that bind to antigen-specific membrane receptors on lymphocytes or to secreted antibodies. 01/27/2025 Firayad A 100  How Does the Immune System Work? When the body senses foreign substances (called antigens), the immune system works to recognize the antigens and get rid of them. B lymphocytes are triggered to make antibodies (also called immunoglobulins). These proteins lock onto specific antigens. After they're made, antibodies usually stay in our bodies in case we have to fight the same germ again. That's why someone who gets sick with a disease, like chickenpox, usually won't get sick from it again 01/27/2025 Firayad A 101 01/27/2025 Firayad A 102 01/27/2025 Firayad A 103  IMMUNOGLOBULINS 01/27/2025 Firayad A 104  Immunoglobulins also known as antibodies are molecules that are produced by the body in response to a foreign substance are serum glycoproteins synthesized by B cells plasma cells They mediate humoral immunity. 01/27/2025 Firayad A 105  Basic structure of immunoglobulins All antibody molecules share the same basic structural characteristics but display remarkable variability in the regions that bind antigens Heavy and Light Chains-  All immunoglobulins have a four chain structure as their basic unit: two identical light chains and two identical heavy chains Hinge Region -The region at which the arms of the antibody molecule forms “Y” is called the 01/27/2025 Firayad A 106  Basic structure of immunoglobulins Variable (V) and Constant (C) Regions Both the heavy and light chain have variable and constant regions 1. Light Chain –VL and CL 2. Heavy Chain -VH and CH Domains –3D images of the immunoglobulin molecule shows that, it is folded into globular regions. These regions are called domains. 1. Light Chain Domains -VL and CL 2. Heavy Chain Domains -VH, CH1 -CH3 (or CH4) 01/27/2025 Firayad A 107 01/27/2025 Firayad A 108  Immunoglobulin Classes, Subclasses, Types and Subtypes Immunoglobulin classes immunoglobulins can be divided into 5 different classes based on differences in the amino acid sequences in the constant region of the heavy chains. All immunoglobulins within a given class will have very similar heavy chain 1. IgG -Gamma (γ) heavy chains (four subclass 1-4) 2. IgM -Micro (μ) heavy chains 3. IgA -Alpha (α) heavy chains (two sub class 1-2) 4. IgD -Delta (δ) heavy chains 5. IgE -Epsilon (ε) heavy chains Immunoglobulin Types -Immunoglobulins can also be classified by the type of light chain that they have. 1. Kappa light chains 2. Lambda light chains 01/27/2025 Firayad A 109  Five different classes, or groups, of immunoglobulins have been established. They are IgM, IgG, IgA, IgE, and IgD. Ig M: - is found mainly in the blood stream. It is the main antibody involved in agglutination reactions. It is a good complement fixing antibody and therefore aids lysis of microbial cells. IgG: - is the only class of immunoglobulin that can cross the placenta from mother to fetus, giving protection several months after birth until a baby’s own immunity begins to develop. 110 IgA: - provides mucous membrane surface protection. It helps, therefore, to protect especially against respiratory tract infections. It is the main immunoglobulin found in secretions in the respiratory, gastrointestinal and genitourinary tracts, and in saliva, tears, and breast milk. Ig E: - It is the main antibody involved in immediate type hypersensitivity anaphylactic reaction. And also in response in some parasitic infections. IgD: - Very little is known about the function of this immunoglobulin. 111 01/27/2025 Firayad A 112  \ 01/27/2025 Firayad A 113 01/27/2025 Firayad A 114  Antibody mediated effector function Neutralization of microbes and microbial toxin Antibodies against microbes and microbial toxins block the binding of these microbes and toxins to cellular receptors Antibody mediated opsonization and phagocytosis Antibodies of the IgG isotype coat (opsonize) microbes and romote their phagocytosis by binding to Fc receptors on phagocyte Activation of the complement system Antibody-Dependent cell –Mediated Cytotoxicity The Fc receptor of NK cells (CDI6), binds to IgG antibodies attached to cells, and the result is lysis of the antibody-coated cells. 01/27/2025 Firayad A 115  Antibody-Dependent cell –Mediated Cytotoxicity 01/27/2025 Firayad A 116  Antibody - Antigen Interactions The Ag-Ab interaction is a biomolecular association similar to enzyme- substrate interaction-Lock and Key Concept Important distinction: Ag-Ab rxn is reversible. Ag-Ab rxn involves non covalent interactions between the epitope of the Ag and the complementary determining regions of Ab. 01/27/2025 Firayad A 117 01/27/2025 Firayad A 118  Ag-Ab reactions Affinity- Strength of the reaction between a single antigenic determinant and a single Ab combining site- Avidity-The overall strength of binding between an Ag with many determinants and multivalent Abs- Specificity: The ability of an individual antibody combining site to react with only one antigenic determinant Cross Specificity: The ability of an individual Ab combining site to react with more than one 01/27/2025 Firayad A 119  Cytokines The term cytokine is a general term used to describe a large group of proteins secreted by cells of innate and adaptive immunity in response to microbes and other cytokines. Cytokines determine and stimulate many diverse responses of cells involved in immunity and inflammation. During immune response activation phase, cytokines stimulate the growth and differentiation of lymphocytes. In the effector phases of innate and adaptive immunity, they activate a different effector cells to eliminate microbes and other antigens. They also stimulate the development of hematopoietic cells. In clinical medicine, cytokines are important as therapeutic 01/27/2025 Firayad A 120  Cytokines 01/27/2025 Firayad A 121  Cytokines by Functional Category Mediators of natural/innate immunity Type I IFN TNF-a Regulators of lymphocytic growth, activation and differentiation IL-2, IL-4, IL-5, IL-12, IL-15 Activators of inflammatory cells Type II IFN IFN-g Stimulators of hematopoiesis IL-3, GM-CSF, IL-7 01/27/2025 Firayad A 122  MHC and Antigen presentation Major histocompatibility complex (MHC) is a cell surface molecule encoded by a large gene familly in all vertebrates. MHC molecules mediate interactions of leukocytes with other leukocytes or body cells. Class I MHC expressed on the surface of nearly all nucleated cells; but vary in concentration on different cell types Major function of Class I gene products is presenting peptide antigens to TC cells. Class II MHC expressed primarily on antigen-presenting cells (macrophages, dendritic cells, and B cells), where they present processed antigenic peptides to TH cells. 01/27/2025 Firayad A 123  Antigen Processing and Presentation Antigen processing involves the interaction of PAMPs and PRRs followed by digestion of the foreign substance by host phagocytic cells. Antigen presentation is the process of displaying peptide antigens associated with MHC molecules to a T cell. The path leading to the association of protein fragments with MHC molecules differs for class I and class II MHC. MHC class I molecules present degradation products derived from intracellular (endogenous) proteins in the cytosol. MHC class II molecules present fragments derived from extracellular (exogenous) proteins that are located in an intracellular compartment. 01/27/2025 Firayad A 124 01/27/2025 Firayad A 125  Reading Assignment Immune response to Infectious Diseases 01/27/2025 Firayad A 126  Hypersensitive Reactions An Immuneresponse eliminates antigen without extensively damaging the host’s tissue. Under certain circumstances, however, this response can have deleterious effects, resulting in significant tissue damage or even death. This inappropriate immune response is termed hypersensitivity or allergy. Although the word hypersensitivity implies an increased response, the response is not always heightened but may, instead, be an inappropriate immune response to an antigen. Hypersensitive reactions may develop in the course of 01/27/2025 Firayad A 127  Classification of Hypersensitivity Based on mechanics involved and time taken for the reactions hypersensitivity reactions are Four Types : Type I (Anaphylactic) Reactions- immediate hypersensitivity Type II (Cytotoxic) Reactions Type III (Immune Complex) Reactions Type IV (Cell-Mediated) Reactions The first three occur within the humoral branch and are mediated by antibody or Ag-Ab complexes. A fourth type depends on reactions 01/27/2025 Firayad A within the cell- 128 01/27/2025 Firayad A 129 01/27/2025 Firayad A 130  Immune response to Bacterial Infections Immunity to extracellular bacteria 1- The innate immunity: a- Complement activation b- Phagocytosis c- The inflammatory response 2- The acquired immune responses: a- The humoral mechanisms (antibodies) “main role” b- Cell mediated immune response “less role” 131 Immunity to intracellular bacteria Intracellular bacteria can activate NK cells, which, in turn, provide an early defense against these bacteria. Intracellular bacterial infections tend to induce a cell- mediated immune response, specifically, delayed type hypersensitivity 132  Immune response to Viral Infections 1. Innate immune response to viral infection Interferon – A group of proteins produced in response to virus infection which stimulates cells to make proteins that block viral transcription, and thus protects them from infection. NK cells – Destroy some virus-infected cells, and are not MHC restricted. – Natural killer cells lyse virally infected cells 133 2. Specific immune response Humoral immunity – Antibodies neutralize virus, preventing its attachment to receptor sites on susceptible cells. Cell mediated immunity(CMI) – CTLs kill virus infected cells directly after recognition of viral antigens on cell surface in association with MHC I. – TH-cells stimulated by viral antigens release cytokines. – Cytokines attract and activate macrophages to kill virus infected cells. 134  Immune response to parasitic Diseases Natural immunity Acquired immunity – Humeral – Cell mediated 135  Hypersensitive Reactions An Immuneresponse eliminates antigen without extensively damaging the host’s tissue. Under certain circumstances, however, this response can have deleterious effects, resulting in significant tissue damage or even death. This inappropriate immune response is termed hypersensitivity or allergy. 136 Although the word hypersensitivity implies an increased response, the response is not always heightened but may, instead, be an inappropriate immune response to an antigen. Hypersensitive reactions may develop in the course of either humoral or cell-mediated responses. 137 Based on mechanics involved and time taken for the reactions hypersensitivity reactions are Four Types : – Type I (Anaphylactic) Reactions – Type II (Cytotoxic) Reactions – Type III (Immune Complex) Reactions – Type IV (Cell-Mediated) Reactions The first three occur within the humoral branch and are mediated by antibody or antigen-antibody complexes. A fourth type depends on reactions within the cell- mediated branch. 138  Type I (Anaphylactic) Reactions It is also known as immediate hypersensitivity. The reaction takes 15-30 minutes from the time of exposure to the antigen. Type I hypersensitivity is mediated by IgE. The primary cellular component in this hypersensitivity is mast cell or basophil. The mechanism of reaction involves preferential production of IgE. 139 General mechanism underlying a type I hypersensitive reaction 140 Type I Reactions Can Be Systemic or Localized SYSTEMIC ANAPHYLAXIS Is a shock-like and often fatal state whose onset occurs within minutes of a type I hypersensitive reaction. A wide range of antigens have been shown to trigger this reaction in susceptible humans, including the venom from bee, wasp, hornet, and ant stings; drugs, such as penicillin, insulin, and antitoxins; and seafood and nuts. If not treated quickly, these reactions can be fatal. Epinephrine is the drug of choice for systemic anaphylactic reactions. 141 LOCALIZED ANAPHYLAXIS (ATOPY) In localized anaphylaxis, the reaction is – limited to a specific target tissue or organ, – Often involving epithelial surfaces at the site of allergen entry. The tendency to manifest localized anaphylactic reactions is inherited and is called atopy. Atopic allergies include: – Allergic rhinitis (hay fever) – Asthma – Food allergies 142 ALLERGIC RHINITIS Results from the reaction of airborne allergens with sensitized mast cells in the conjunctivae and nasal mucosa to induce the release of pharmacologically active mediators from mast cells. The symptoms include watery exudation of the conjunctivae, nasal mucosa, and upper respiratory tract, as well as sneezing and coughing. 143 ASTHMA Airborne or blood-borne allergens, such as pollens, dust, fumes, insect products, or viral antigens, trigger an asthmatic attack (allergic asthma). Can be induced by exercise or cold, apparently independently of allergen stimulation (intrinsic asthma) The reaction develops in the lower respiratory tract. The resulting contraction of the bronchial smooth muscles leads to bronchoconstriction. Airway edema, mucus secretion, and inflammation contribute to the bronchial constriction and to airway obstruction. 144 FOOD ALLERGIES Various foods also can induce localized anaphylaxis in allergic individuals. Allergen cross linking of IgE on mast cells along the upper or lower gastrointestinal tract can induce localized smooth-muscle contraction and vasodilation and thus such symptoms as vomiting or diarrhea. Mast-cell degranulation along the gut can increase the permeability of mucous membranes, so that the allergen enters the bloodstream and various symptoms can ensue, depending on where the allergen is deposited. For example: asthma 145  Type II (Cytotoxic) Reactions Mediated, primarily, by antibodies of IgM or IgG class and complement The reaction time is minutes to hours. Affect a variety of organs and tissues. 146 147  Examples of type II hypersensitive reactions – Transfusion Reactions – Hemolytic Disease of the Newborn – Drug-Induced Hemolytic Anemia Transfusion Reactions Antibodies to the A, B, and O antigens, called isohemagglutinins are usually of the IgM class. Antibodies to other blood-group antigens may result from repeated blood transfusions because minor allelic differences in these antigens can stimulate antibody production.These antibodies are usually of the IgG class. 148  The clinical manifestations of transfusion reactions result from massive intravascular hemolysis of the transfused red blood cells by antibody plus complement. Hemolytic Disease of the Newborn Hemolytic disease of the newborn develops when maternal IgG antibodies specific for fetal blood-group antigens cross the placenta and destroy fetal red blood cells. Caused by Rh incompatibility 149 Drug-Induced Hemolytic Anemia Certain antibiotics (e.g., penicillin, cephalosporin, and streptomycin) can adsorb nonspecifically to proteins on RBC membranes, forming a complex similar to a hapten-carrier complex. In some patients, such drug-protein complexes induce formation of antibodies, which then bind to the adsorbed drug on red blood cells, inducing complement mediated lysis and thus progressive anemia. 150  Type III (Immune Complex) Reactions When large amounts of antigen bind to antibody, immune complexes can form. If antigen is in excess, small complexes form; because these are not easily cleared by the phagocytic cells, they can cause tissue-damaging Antibodies are mostly of IgG class, although IgM may also be involved. The antigen may be exogenous (chronic bacterial, viral or parasitic infections), or endogenous (non-organ specific autoimmunity: e.g., systemic lupus eythematosus-SLE). 151 152  When the complexes are deposited in tissue very near the site of antigen entry, a localized reaction develops. example Arthus reaction When the complexes are formed in the blood, a reaction can develop wherever the complexes are deposited. Example serum sickness. Complex deposition in serum sickness frequently observed – On blood-vessel walls – In the synovial membrane of joints – On the glomerular basement membrane of the kidney – On the choroid plexus of the brain. 153  Formation of circulating immune complexes contributes to the pathogenesis of a number of conditions other than serum sickness. These include the following: Autoimmune Diseases: – Systemic lupus erythematosus – Rheumatoid arthritis Drug Reactions: – Allergies to penicillin and sulfonamides 154  Infectious Diseases – Poststreptococcal glomerulonephritis – Meningitis – Hepatitis – Mononucleosis – Malaria – Trypanosomiasis The deposition of these complexes initiates a reaction that results in the recruitment of neutrophils to the site. The tissue there is injured as a consequence of granular release from the neutrophil. 155  Type IV (Cell-Mediated) Reactions DTH response does cause extensive tissue damage and is in itself pathologic. In many cases tissue damage is limited, and the response plays an important role in defense against intracellular pathogens and contact antigens. The hallmarks of a type IV reaction are the delay in time required for the reaction to develop and the recruitment of macrophages as opposed to neutrophils, as found in a type III reaction. Macrophages are the major component of the infiltrate that surrounds the site of inflammation 156 Intracellular pathogens and contact antigens that induce delayed-type (type IV) hypersensitivity 157  Phases of the DTH Response Sensitization phase DTH response begins with an initial sensitization phase of 1–2 weeks after primary contact with an antigen. During this period, TH cells are activated and clonally expanded by antigen presented together with the requisite class II MHC molecule on an appropriate antigen presenting cell A variety of antigen-presenting cells have been shown to be involved in the activation of a DTH response, including: – Langerhans cells – Macrophages. 158  T cells activated during the sensitization phase are CD4+, primarily of the TH1 subtype. Efector phase A subsequent exposure to the antigen induces the effector phase of the DTH response. In the effector phase, TH1 cells secrete a variety of cytokines that recruit and activate macrophages and other nonspecific inflammatory cells. A DTH response normally does not become apparent until an average of 24 h after the second contact with the antigen; the response generally peaks 48–72 h after second contact. 159  The delayed onset of this response reflects the time required for the cytokines to induce localized influxes of macrophages and their activation DTH response is important in host defense against parasites and bacteria that live within cells, where circulating antibodies cannot reach them. 160 Overview of the DTH response Source: Kuby. Immunology 2007 5th ed). Examples of DTH Tuberculin-type hypersensitivity Contact Dermatitis Contact Dermatitis Many contact-dermatitis reactions, including the responses to formaldehyde, trinitrophenol, nickel, turpentine, and active agents in various cosmetics and hair dyes, poison oak, and poison ivy, are mediated by TH1 cells. Most of these substances are small molecules that can complex with skin proteins. 162 DTH Reaction Is Detected with a Skin Test The presence of a DTH reaction can be measured experimentally by injecting antigen intradermally and observing whether a characteristic skin lesion develops at the injection site. A positive skin-test reaction indicates that the individual has a population of sensitized TH1 cells specific for the test antigen. – For example, to determine whether an individual has been exposed to M. tuberculosis, PPD, a protein derived from the cell wall of this mycobacterium, is injected intradermally. – Development of a red,slightly swollen, firm lesion at the site between 48 and 72 h later indicates previous exposure. 164  Immunization The process of inducing immunity in individual. It protects an individual or community from infectious disease. Immunization could be passive or active. Passive Immunization Direct administration of antibody that has been produced in an animal or that are obtained from another human. Passive acquired immunization may be given when the body does not produce antibodies in response to an infection, or does not produce them rapidly enough. Protection is immediate but short lived 165 Active immunization It is known as vaccination Stimulation of the immune system with known antigen, which could be enhanced in contact with the same antigen again. The purpose of vaccination is to put the immune system on the alert against the particular infectious agent. 166  Vaccine Vaccination is the administration of antigenic material (the vaccine) to produce immunity to a disease. Vaccination is generally considered to be the most effective and cost-effective method of preventing infectious diseases Vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains a small amount of an agent that resembles a microorganism. The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters. 167  Vaccines protect the – vaccinated individual, – protect society. A community with many vaccinated people – protects the few who cannot be vaccinated—such as young children. – indirectly protects unvaccinated from exposure to disease).= HERD IMMUNITY 168  Type of vaccines Vaccines are dead or inactivated organisms or purified products derived from them. There are several types of vaccines currently in use.[ Killed vaccine Vaccines containing killed microorganisms - these are previously virulent micro-organisms which have been killed with chemicals or heat. E.g. whooping cough, typhoid fever, Plague, cholera, pertussis, rabies, and hepatitis A vaccine. 169 Attenuated vaccine Some vaccines contain live, attenuated virus microorganisms. These are live micro-organisms that have been cultivated under conditions that disable their virulent properties, or which use closely-related but less dangerous organisms to produce a broad immune response. They typically provoke more durable immunological responses and are the preferred type for healthy adults. E.g. Polio, measles, rubella, yellow fever, varicella- zoster, and tuberculosis. 170 Toxoid vaccine These are inactivated toxic compounds in cases where these (rather than the micro-organism itself) cause illness. E.g Tetanus toxoid, diphtheria toxoid vaccine. Subunit vaccine Rather than introducing an inactivated or attenuated micro- organism to an immune system (which would constitute a "whole-agent" vaccine), a fragment of it can create an immune response. E.g. streptococcus pneumonia, Neisseria meningitidis, Hemophilus influenza, hepatitis B virus vaccine. 171 Conjugate vaccine Certain bacteria have polysaccharide outer coats that are poorly immunogenic. By linking these outer coats to proteins (e.g. toxins), the immune system can be led to recognize the polysaccharide as if it were a protein antigen. This approach is used in the Haemophilus influenzae type B vaccine. 172  Immunotherapy Treatment of disease by inducing immune response Enhancing Suppressing an immune system 173 Immunotherapy of cancer Immunotherapy seems to offer great promise as a new dimension in cancer treatment, but it is still very much in its infancy. Immunotherapies involving certain cytokines and antibodies have now become part of standard cancer treatment. Other examples of immunotherapy remain experimental 1) Interferons and Other Cytokines Interferons belong to a group of proteins known as cytokines. They are produced naturally by white blood cells in the body (or in the laboratory) in response to infection, inflammation, or stimulation. They have been used as a treatment for certain viral diseases, including hepatitis B. 174  Interferon-alpha was one of the first cytokines to show an antitumor effect, and it is able to slow tumor growth directly, as well as help to activate the immune system. Interferon-alpha is now commonly used for the treatment of a number of cancers, including multiple myeloma, chronic myelogenous leukemia, hairy cell leukemia, and malignant melanoma. Other cytokines with antitumor activity include the interleukins (e.g., IL-2) and tumor necrosis factor. IL-2 is frequently used to treat kindey cancer and melanoma. 175 2) Monoclonal Antibodies Another important biological therapy involves antibodies against cancer cells or cancer-associated targets. Monoclonal antibodies are artificial antibodies against a particular target (the "antigen") and are produced in the laboratory. As therapy for cancer, monoclonal antibodies can be injected into patients to seek out the cancer cells, potentially leading to disruption of cancer cell activities or to enhancement of the immune response againast the cancer. 176  Researchers also are studying ways of linking cytotoxic drugs, toxins, or radioisotopes to monoclonal antibodies to enhance their effectiveness against cancer cells. In this case, the antibodies would function as a targeted delivery mechanism; the result would be like a "guided missile, " capable of seeking out a specific target-a cancer cell. 177 Immunotherapy for Allergic Conditions: Allergen immunotherapy involves administering gradually increasing amounts of an allergen to a patient over several months. The injections are first given on a weekly or bi-weekly basis, and when the maintenance level is reached, eventually on a monthly basis. This process reduces symptoms that are otherwise triggered by allergen exposure. This form is of treatment is the closest thing to a "cure" for allergic symptoms. 178  Immunologic Tolerance and Autoimmunity Tolerance refers to the specific non-reactivity to an antigen from the previous exposure to the same antigen. While the most important form of tolerance is non- reactivity to self-antigens, it is possible to induce tolerance to non-self (foreiegn) antigens. When an antigen induces tolerance it is referred to as a toleragen. Autoimmunity is immune system response to self component. 01/27/2025 Firayad A 179  Immunodeficiency What is Immunodeficiency? A failing of one or more of the body’s defensive mechanisms resulting in morbidity or mortality. Immunodeficiency may be Primary or Secondary. Primary: Inherited genetic defects in immune cell development or function or inherited deficiency on a particular immune molecule. Defect in the early hematopoiesis which involves stem cells results in reticular dysgenesis that leads to general immune defects and subsequent susceptibility to infections. This condition is often fatal. Secondary: a loss of previously functional immunity as a result of acquired as a consequence of other diseases or environmental factors (e.g. infection, malignancy, aging, starvation, medication, drugs 01/27/2025 Firayad A 180 Clinical features associated with immunodeficiency Feature frequently present and highly suspicious:  Chronic infection  Recurrent infection (more than expected)  Unusual microbial agents  Incomplete clearing of infection 01/27/2025  Incomplete response to treatment Firayad A 181  Vaccines Vaccines are biological substances that stimulate the person’s immune system. – produce an immune response identical to that produced by the natural infection. Vaccines protect the vaccinated individual and protect society. A community with many vaccinated people protects the few who cannot be vaccinated such as young children=HERD IMMUNITY Aim of an ideal vaccine: – To produce the same immune protection which usually follows natural infection but without causing disease – To generate long-lasting immunity – To interrupt spread of infection 01/27/2025 Firayad A 182  Designing Vaccines for Active Immunization Many common vaccines use Inactivated (killed), but still antigenic or live/altered – attenuated microorganisms. – Caused to loose pathogenicity (cultured in abnormal conditions) Substance (e.g., protein, polysaccharide) from pathogen, capable of producing an immune response 01/27/2025 Firayad A 183 Disinfection, Decontamination And Sterilization  Methods of sterilization and disinfection Physical Chemical methods methods - Heat (dry heat and moist heat) - Radiation - Filtration Firayad A 185 Firayad A 186  Physical methods 2)Dry heat Red heat Flaming, Incineration 1)Moist Heat Hot air  Autoclave(At a pressure of 15 oven(Sterilization requires lbs,temperature is 121°C, 15 processing for 1 hour at minutes) 171°C, 2 hours at 160°C, or  Boiling water (100 °C) for 20 16 hours at 121°C)  Steam at 100oC for 90min  Tyndallization (Intermittent steaming)(Steaming of the material 3)Radiation is done at 100 °C for 30 minutes for Gamma rays, x-rays, beta three consecutive days) rays, cosmic rays,  Pasteurization (62°C for 30 ultraviolet light, and even minutes or 72 °C for 15 seconds visible light are all forms of  Freezing : (At 0 °C or less temp.) radiation. When these rays  Lyophilization (freeze-drying strike an organism, energy may be absorbed by the Firayad A cells, often causing cell 187 damage or death. Since Time-Temperature-Pressure Level Relationship in Autoclaving Temperature Time Pressure level 1210c 15 minutes 15 lb/inch2 1260c 10 minutes 20 lb/inch2 1340c 3 minutes 30 lb/inch2 Firayad A 188  Factors affecting sterilization by heat Nature of heat: Moist heat is more effective than dry heat Temperature and time: temperature and time are inversely proportional. As temperature increases the time taken decreases. Number of microorganisms: More the number of microorganisms, higher the temperature or longer the duration required. Nature of microorganism: Depends on species and strain of microorganism, sensitivity to heat may vary. Spores are highly resistant to heat. Type of material: particles that are heavily contaminated require higher temperature or prolonged exposure. Certain heat sensitive prticles must be sterilized at lower temperature. Presence of organic material: Organic materials such as protein, sugars, oils and fats increase the time required. Firayad A 189 Radiation Two types of radiation are used, ionizing and non-ionizing. Non-ionizing rays: Rays of wavelength longer than the visible light are non-ionizing. Microbicidal wavelength of UV rays lie in the range of 200-280 nm, with 260 nm being most effective. Microorganisms such as bacteria, viruses, yeast, etc. that are exposed to the effective UV radiation are inactivated within seconds. Ionizing rays: Ionizing rays are of two types, particulate and electromagnetic rays. Electromagnetic rays such as gamma rays have more penetrative power than electron beam but Firayad A 190  Filtration Filtration does not kill microbes, it is used to remove microbes from heat labile liquids such as serum, antibiotic solutions, sugar solutions, urea solution. Membrane filters: These filters are made from a variety of polymeric materials such as cellulose nitrate and cellulose diacetate, Cellulose diacetate membranes have a pore diameter ranging from 0.015 μm to 12 μm. These filters are sterilized by autoclaving. Air Filters: Air can be filtered using HEPA (High Efficiency Particle Air) filters. They are usually used in biological safety cabinets. HEPA filters Firayad A 191 are at least 99.97% efficient for removing particles >0.3 μm in Chemical Sterilization is the process of removal of microorganisms by the use of chemical bactericidal agents. Firayad A 192  Ethylene oxide is the most commonly used gas vapor sterilant. Sterilization with formaldehyde gas is also used possible but limited because the chemical is carcinogenic. – Its use is restricted primarily to sterilization of HEPA filters. Hydrogen peroxide vapors are effective sterilants because of the oxidizing nature of the gas. This sterilant is used for the sterilization of instruments. A variation is plasma gas sterilization.  Peracetic acid and glutaraldehyde. Peracetic acid, an oxidizing agent, has excellent activity, and the end products (i.e., acetic acid and oxygen) are nontoxic. In contrast, safety is a concern with glutaraldehyde, and care must be used when handling this chemical. Firayad A 193  Disinfection Disinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on the objects. Disinfection does not necessarily kill all microorganisms, especially non-resistant bacterial spores; it is less effective than sterilisation. The effectiveness of disinfecting procedures is influenced by the nature of the item to be disinfected, number and resilience of the contaminating organisms, amount of organic material present (which can inactivate the disinfectant), type and concentration of disinfectant, and duration and temperature of exposure. Firayad A 194 Firayad A 195  Level of disinfectants High-level disinfectants are used for items that cannot withstand sterilization procedures Examples of high-level disinfectants include treatment with moist heat and use of liquids such as formaldehyde, glutaraldehyde, hydrogen peroxide, peracetic acid, and chlorine compounds. Intermediate-level disinfectants are used to clean surfaces or instruments in which contamination with bacterial spores and other highly resilient organisms is unlikely. These have been referred to as semi-critical instruments and devices. Example are Iodophore compounds, Phenolic Compounds and Alcohols (ethanol and isopropanol) Firayad A 196  Antisepsis Antiseptic agents are used to reduce the number of microbes on skin surfaces. These compounds are selected for their safety and efficacy. Alcohols have excellent activity against all groups of organisms, except spores, and Alcohols are nontoxic, although they tend to dry the skin surface because they remove lipids. Iodophors are also excellent skin antiseptic agents, having a range of activity similar to that of alcohols. They are slightly more toxic to the skin than is alcohol Iodophors and iodine preparations are frequently used with alcohols for disinfecting the skin surface. Firayad A 197