Microbiology by Dr. Mohamed Hegazi Mahgoub PDF

# Microbiology by Dr. Mohamed Hegazi Mahgoub ## Contents - **1General microbiology** - **1.1 Definition of microbiology** - **1.2A historical overview of microbiology** - **1.3Classification of microorganis** - **1.4Bacteria** - **1.4.1Bacterial Morphology** - *...

# Microbiology by Dr. Mohamed Hegazi Mahgoub ## Contents - **1General microbiology** - **1.1 Definition of microbiology** - **1.2A historical overview of microbiology** - **1.3Classification of microorganis** - **1.4Bacteria** - **1.4.1Bacterial Morphology** - **Size:** Bacteria range in size from about 0.125 to 10 micrometer (μm). (1 μm = 0.001 mm = 10^-6 meter). - **Shape:** Bacteria are classified according shape into: Spherical or cocci, Rods or bacilli and Spiral-shaped (called spirilla or spirochetes) - **Arrangement:** (Single, pairs, Tetrads, Chain and grapelike clusters). - **1.4.2 Structure of the bacterial cell** - **1.4.2.1 Structures that found in all bacteria** - Cell wall, responsible for bacterial shape and determining the reaction to Gram stain - Cytoplasmic membrane, controlling entry and exit of materials into and out of the cell - Cytoplasm, is a fluid which located inside it all components of bacteria - Genetic material, (DNA) (bacteria do not contain a true nucleus) - **1.4.2.2 Structures that may be found in some bacteria** - Capsule, protect bacteria from phagocytosis - Flagella, responsible for motility - pili, help bacteria adherence to surfaces - **1.4.2.3 Sporulation** - Sporulation is a process of formation of endospores, a highly resistant phase of some bacteria e.g. Clostridium tetani. Spores are highly resistant to heat and chemicals. - It can destroy only by autoclaving at 121° C, for 15 - 30 minutes. It can remain dormant for many years, if environmental conditions are unfavorable. When environmental conditions improve, it can convert to vegetative bacterial cell again - NB Sporulation is not a means of reproduction, since one cell produces one spore that germinates into one cell - **1.4.3 Bacterial nutrition** - Bacteria as any living organism need to carbon, nitrogen, sulfur, phosphorus and inorganic ions, such as potassium, sodium, iron, magnesium, calcium, chloride ...etc. - **1.4.4 Environmental Conditions** - **1.4.4.1 Temperature** - Bactria classified according their optimal temperature ranges for growth into, Psychrophiles, Mesophiles and Thermophiles - **1.4.4.2 Oxygen** - Bacteria are classified according their oxygen requirements into: Obligate Aerobes, Obligate Anaerobes, Facultative Anaerobes, Aerotolerant organisms and Microaerophiles - **1.4.5 Bacterial growth curve** - Bacteria reproduce by binary fission. The bacterial growth curve proceed through four stages as follows - **1.4.5.1 Lag phase:** - This stage begins when the culture was inoculated with bacteria in vitro and is matched by the arrival of the bacteria to the site of infection in vivo (incubation period). This stage is characterized by increased activity in metabolism, with no increase in number. This stage may vary from 1 hour to several days according to the type of bacteria and environmental condition. - **1.4.5.2 Log phase** - This phase is characterized by rapid increase number of bacteria, colonies which appear in vitro. Symptoms of disease in vivo (acute infection). The bacterial cells are small and uniformly stained, and they are sensitive to adverse conditions, such as antibiotics. - **1.4.5.3 Stationary phase** - In vitro, the nutrients begin to decrease, as well as oxygen, and toxic waste accumulates in the environment. - In vivo the production of antibodies or taken of antibiotics begins (chronic stage), so the number of bacteria is almost constant. - **1.4.5.4 Decline phase** - During this phase, the bacterial population decrease due to death of cells because of accumulation of toxic products and autolytic enzymes and exhaustion of nutrients. (It's known as recovery period in vivo). - **1.4.6 Bacterial staining** - Stains are chemical or organic colored substances that have the ability to combine with compounds of microbial cells and give them the color of the stains The commonest stain which use on bacteriology is Gram stain. Its classified bacteria into two groups (Gram positive and Gram negative bacteria) - **1.4.7 Bacterial cultivation** - Bacterial cultivation is procedure used to facilitate the identification of pathogenic microorganisms, where grown them on artificial mediums which provide the necessary biological, chemical and physical requirements for the growth and reproduction. These media are usually used for bacteria and fungi, but they are not suitable for obligate intracellular parasite, such as viruses, chlamydia and rickettsia. - Culture mediums are classified according to form into solid, semi-solid and liquid cultures; and according to composition into: - Simple (basic) media such as liquid Peptone water, semisolid and solid nutrient agar - Enriched media such as blood agar and chocolate agar - Selective media such as Lowenstein Jensen and TCBS agar - Indicator media such as MacConkey agar - **1.5 Fungi** - **1.5.1 Structure and general properties of fungi** - The fungal cell is eukaryotic, including a nucleus with a nucleolus, nuclear membrane, and linear chromosomes. Fungal cells have a rigid cell wall. The composition of that wall different from bacteria and plants, where does not contain peptidoglycan, or lipopolysaccharide. - Fungi grow in two basic forms unicellular as yeasts or multicellular as molds. - **1.6 Viruses** - **1.6.1 Structure of Viruses** - Nucleic Acid, (a genome) DNA or RNA - Capsid, a protein coated that surrounds the NA. It is responsible for viral symmetry (cubic icosahedral, helical or complex). - Envelope, it is a lipoprotein that is present outside the capsid, in big viruses mainly. - **1.7 Normal microbial flora (microbiota) = microflora** - Microflora term is referring to the microorganisms that live collectively on or in the body but do not cause disease. - These microorganisms begin their journey with human at birth, were the fetus acquires certain of them that may become permanently or temporarily associated with it through birth. Over time, the number are increases, so if we know an adult human body consists of approximately 10¹³ (10 trillion) cells, It contain an additional 10¹⁴ (100 trillion) microorganisms. Thus, there are 10 times more microbial cells on or in the human body than there are cells making up the body - Most of these organisms are commensals; they obtain nutrients from host secretions waste found on the surfaces of skin and mucous membranes. - Bacteria are the predominant component of the normal flora, they are found in most particularly in the gastrointestinal tract, where hundreds different species have been counted which lives in gastrointestinal, the count of these microorganisms may reach to more than 10¹² per gm of colon content, they are found also on the skin surface, on mucous membranes, and in the passageways of the digestive, respiratory, and reproductive systems, arranged into two groups, Resident microflora and Transient microflora. - **1.7.1 Beneficial Effects of normal flora** - The resident microflora of certain areas plays an important role in maintaining health and normal function: - The microflora of the intestinal tract aid in the digestion and absorption of nutrients and supply the body's needs of some vitamins, by synthesize these vitamins such as vitamin K and several B vitamins - Prevention of colonization by pathogens, where Compete with them for essential nutrients, some of microflora can produce antimicrobial substances which have a harmful effect on pathogens. - Stimulus for the development of the immune system, where microflora colonization of the newborn infants acts as a powerful stimulus for the development of the immune system - **1.7.2 Harmful Effects of Normal Flora** - Some microflora can become pathogenic and called opportunistic, under certain conditions, such as immunocompromised individuals, also if the microflora reach to different from their usual Sites - Confusion in diagnosis: They cause confusion in diagnosis due to their ubiquitous presence in the body, and their morphological similarity with some pathogens. - **1.7.3 Probiotics** - Newly appeared term Probiotics that refers to the consumption of certain microorganisms in an effort to improve overall health and the functioning of the body's microflora. One of the most important of these microorganisms, Lactobacillus and Bifidobacterium which is added to some foodstuffs such as dairy products. - **2 Basics of immunity** - **2.1 Immunity definition** - The ability of the body to resist or fight off infection and disease which caused by an infectious agent, such as a bacteria or viruses. - **2.2 Immunology** - It is one branch of the biological sciences which interested in studying of structure and function of the immune system - **2.3 Antigen** - Is any foreign substance, which, if entered into an animal or human body, provokes the immune system to form antibody or cell mediate immunity. The antigen (Ag) can react specifically with antibody or cell induced by it. Bacteria and bacterial products are antigenic, they are proteins, some Antigens may be are polysaccharides. - **2.4 Antibody** - Is a gamma globulin that appears in the serum and tissue fluids of animal or human in response to introduction of an Ag and when mixed with Ag react specifically with it in some observable way. - Antibody (Ab) has specific attachment sites for Ag molecules, are secreted by plasma cells which are derived from B lymphocytes. There are five classes of immunoglobulins have been identified in humans and other higher vertebrates, each class has distinguishing properties. The five classes are IgG, IgA, IgM, IgE, and IgD - **2.5 Immune response** - The collective and coordinated response against the introduction of foreign substances in an individual, which occur by the cells and molecules of the immune system - **2.6 Immune system** - The immune system is defer from another systems of human, it distribute at all of the body and include cells, tissues, and molecules. - **2.7 Structure of Immune System** - **2.7.1 Organs** - Include, Tonsils, Thymus, Lymph nodes, Spleen, Peyer's patches, Appendix, Lymphatic vessels and Bone marrow - **2.7.2 Cells** - Include, (Lymphocytes T, B and NK), Monocytes (Macrophage) and Granulocytes (neutrophils, eosinophils and basophils) - **2.7.3 Molecules** - Such as Antibodies, Complement, Cytokines and Interferon - **2.8 Types of immunity** - **2.8.1 Innate or natural immunity** - It provides the body's non-specific defense for body against invasion by microorganisms, act against any type of invading agent. Often this function is performed before the adaptive defense mechanisms are activated - Furthermore it, the innate system's action is necessary to activate the adaptive system responses. Innate defenses include the following: - **2.8.1.1 Physical barriers** - Include, the intact skin, intact mucous membranes, blinking, hair of nose, coughing and sneezing. - **2.8.1.2 Chemical barriers** - There are many chemical barriers that control microbial growth. For example; Lysozymes, Sweat and The high acidity of the stomach - **2.8.1.3 Defensive Cells** - Consisting of certain cells (Leukocytes) that engulf (phagocytize) invading microorganisms, and it is considered are important to both adaptive and innate host defenses. - **2.8.1.4 Inflammation** - Is the body's defensive response to tissue damage from microbial infection. (It is also a response to mechanical or chemical injury, such as cuts, burns, sunburn, acids, and allergies). It is characterized with: increase in temperature, redness, swelling, and pain. - Acute inflammation functions to, kill invading microbes, clear away tissue debris, and repair injured tissue. - **2.8.1.5 Fever** - Fever has several beneficial roles: - It raises the body temperature above the optimum temperature for growth of many pathogens. which lead to slows their rate of growth, - At the higher temperatures of fever, some microbial enzymes or toxins may be inactivated. - Fever can heighten the level of immune responses by increasing the rate of chemical reactions in the body. - **2.8.1.6 Molecular defenses** - There are many non-specific molecules present in the tissue and body fluids such as interferon and complement which destroy or impede invading microbes. - **2.8.2 Adaptive Immunity (acquired)** - Acquired immunity refers to the resistance that an individual acquires during his lifetime in some manner other than by heredity, provide specific defense for the host, and divided into active or passive and obtained by natural or artificial mechanisms - **2.8.2.1 Active Immunity** - Active Immunity can be naturally acquired by having a specific microbial disease, where the immune system responds to clinical or subclinical infection by a microbe, and activates T cells, produces antibodies, that inactivate or destroy the antigen, then originate a memory that protect against future invasions by the same agent. The duration of this immunity varies with the type of pathogen. It may be long term or life-long following many viral diseases such as chickenpox or measles, or short-lived in some diseases, such as influenza or common cold. - On the other hand, artificially acquired active immunity can produced, when a person is injected with a vaccine containing live weakened or dead organisms or their toxins. - **2.8.2.2 Passive immunity** - Antibodies in this case do not made of the host's immune system so it is called passive immunity, and it can be naturally acquired from antibodies which made by a mother's immune system, transferred to a fetus across the placenta or to an infant in colostrum and breast milk. - Artificially acquired passive immunity is produced when antibodies made by other hosts are introduced into a new host. For example, scorpion Antivenins are antibodies produced in another animal, such as horses or rabbits, then injected to the person who was stung by the scorpion. Ready-made antibodies and the immunity they confer persist for a few weeks to a few months. - **2.9 Primary and secondary immune response** - The primary response to an antigen occurs when the antigen is first recognized by host's lymphocyte B cells. After recognizing the antigen, B cells divide to form plasma cells, which begin to synthesize antibodies (firstly IgM then IgG) and memory cells. Antibodies IgM begin to appear in the blood plasma, which can bind to the antigen directly. And they increase in concentration over a period of 1 to 10 weeks, then declines rapidly to undetectable levels. While the memory cells will persist in lymphoid tissues and have ability to recognize the same antigen - The secondary response occurs when the same antigen invades the host for the second time, where the antigen recognized by memory cells which are present in great numbers that makes the secondary response much faster than the primary response. Some memory cells divide rapidly, producing plasma cells, and others proliferate and form more memory cells. Plasma cells quickly synthesize and release large quantities of antibodies. The secondary response is characterized by a rapid increase in antibodies, most of which are IgG. - **3 Infection control** - **3.1 Chain of infection** - Infectious disease can spread from person to person, this process called the chain of infection, which can only occur when all six links in the chain are intact. Infection Control principles are aimed at breaking one or more links in this chain to prevent infection. - **3.1.1 Infectious agent:** - Pathogens that cause communicable diseases include bacteria, viruses, fungi or parasites. - **3.1.2 Reservoir** - The reservoir (source) is a host which allows the pathogen to survive but may or may not multiply. - There are three common reservoirs - **a. Human:** acute clinical case, asymptomatic cases or carriers. - **A carrier:** is a person who shows no recognizable signs or symptoms of a disease but is capable of spreading disease to others, such as: - Persons in the prodromal period of infectious disease. - Convalescent carriers: are those who recovered from the disease but still can transmit infection to others (e.g. Cholera) - Chronic carriers, may continue to have organisms present for very long periods of time (e.g. Typhoid) - **b. Animal reservoirs:** - Zoonotic diseases refer to an infectious disease that primarily exist in animals but can transmit under natural conditions to humans. - **c. Environmental reservoirs:** - Plants, soil, and water in the environment are reservoirs for some infectious agents. - **3.1.3 Portal of exit** - Portal of exit is the pathway by which the microorganism leaves the host. For example, by coughs or sneezes through the mouth and nose in case of respiratory organisms - **3.1.4 Modes of transmission** - It is how transmitted of infectious agent from the reservoir to the host, It is can occur by many routes such as contact (direct or indirect), inhalation (droplets and dust), ingestion (food and water), insects, and Iatrogenic routes. - **3.1.5 Portal of entry** - The portal of entry refers to the manner in which a pathogen enters a susceptible host. There are 4 important portals of entry of microorganisms; to transmission infection includes Skin, Respiratory tract, gastrointestinal tract and Genital Tract - **3.1.6 Susceptible host** - A person with a weakened immune system and he is susceptible to the infectious agent. Susceptibility of a host depends on genetic or constitutional factors, specific immunity, and nonspecific factors that affect an individual's ability to resist infection or to limit pathogenicity. An individual's genetic makeup may either increase or decrease susceptibility. - **3.1.7 Opportunities to break the chain of infection** - If the chain is not broken the infectious organism is able to go on to develop disease in another person. - There are many opportunities to stop the spread of infection. - The infectious agent is eliminated, inactivated or cannot exit the reservoir - The portals of exit are contained through safe infection control practices - The transmission between objects or people does not occur due to barriers and safe infection control practices - The portals of entry are protected other persons receiving health care are not susceptible - **3.2 Nosocomial infection (Health care Associated Infections HCAIS)** - According to World Health Organization (WHO) 2011, HCAIs defined as 'An infection occurring in a patient during the process of care in a hospital or other healthcare facility, after 48 - 72 hrs from entering hospital, This includes infections acquired in the hospital but appearing after discharge and also occupational infections amongst staff of the facility'. Many of these pathogens have antibiotic resistance - **3.3 Sources of nosocomial infection** - Endogenous infections, which caused by opportunistic bacteria which come from a patient's own normal flora, and may be acquired due to Immunological weakened or in the course of invasive procedure. - Exogenous infections, occur by sources outside of the patient's own body. Such as other patients, Healthcare personnel and contaminated medical devices. - **3.4 Standard Precautions (Prevention Strategies)** - They are standards of care, designed to reduce the risk of transmission of microorganisms, where WHO recommends employing basic hygiene principles through standard precaution which include, hand hygiene, use of personal protective equipment (PPE), routine environment cleaning, cough etiquette and aseptic technique. These precautions aim to protect health care personnel, patients and environment from pathogens - **3.4.1 Hand hygiene** - Hand hygiene is one of the most important procedures for preventing the transmission of hospital-acquired infections, and includes: - Routine hand washing, (Remove dirt and transient flora): - Washing hands with plain soap and water - Antisepsis Hand washing, (Remove dirt, transient and reduce resident flora): (before minor invasive procedures) - Rubbing hands with an alcoholic hand preparation (solutions or gels) or washing hands with water and antiseptic soap e.g. iodophor (betadine) or chlorhexidine. - Surgical hand scrub, (Remove debris, transient flora, reduce the resident flora count to a minimum, and Inhibit rapid rebound growth of them. (Before surgery) - Washing hands and forearms with antimicrobial soap for 2-6 minutes. Rubbing hands and forearms with alcoholic preparation after washing with plain soap. - **3.4.2 The 5 moments for hand hygiene** - **Moment 1:** - Before touching a patient - e.g. shaking hands, helping a patient to move around, clinical examination - e.g. oral/dental care, secretion aspiration, wound dressing, catheter insertion, preparation of food, medications - **Moment 2:** - Before clean/aseptic procedure - After blood or body fluid exposure - e.g. oral/dental care, secretion aspiration, drawing and manipulating blood, clearing up urine, faeces, handling waste - **Moment 3:** - After touching a patient - e.g. shaking hands, helping a patient to move around, and clinical examination. - **Moment 4:** - After touching patient surroundings - e.g. changing bed linen, perfusion speed adjustment - **3.4.3 Personal protective equipment (PPE)** - Personal protective equipment (PPE) involves use of protective barriers which can reduce the risk of exposure of health care personnel to from the risk of contamination with blood, body fluids and secretions or exposure to chemicals, certain airborne agents, also prevent the transmission of microorganisms to both patients and staff. - The common PPE includes, Head coverings, Eye and face protection, Masks, Gloves, Gowns and aprons and Foot protection - **3.4.3.1 Common mistakes when using PPE** - The incorrect use of gloves and disposable plastic aprons (both under-use and over-use) can increase the risk of cross-infection to patients, and contaminate equipment and the environment. - Wear apron or gloves is often one of the first things that healthcare workers do in preparation for a task or patient care activity. Whereas it should be the last thing that the healthcare worker does before action with the task or patient. - Healthcare workers must not leave a bay or a side room wearing an apron and/or gloves unless there is an emergency or they are removing a bedpan or carrying a urinal (PPE will provide protection from body fluid contact, and the wearing of PPE on leaving the patient's bedside in this instance is a continuation of that patient's care), or transporting dirty equipment to the waste room, in which case as soon as the task has been completed, the PPE must be removed and hands decontaminated or washed. - PPE dispensers must be located appropriately (e.g. outside bays and side rooms). Gloves should not be kept in bathrooms - they will become easily contaminated with faecal organisms such as Clostridium difficile spores - The wearing of gloves does not replace the need for hand hygiene, and wearing gloves inappropriately means that opportunities for hand decontamination are missed and the risk of cross-infection to patients is increased. - **3.4.4 The safe handling and disposal of sharps** - Sharps or needle stick injuries can occur through the handling of clinical waste, contact with blood and other high-risk body fluids, procedures such as cannulation and venipuncture, and surgery. - On the following, the most important of recommendations to prevention of sharps injuries - Eliminate any unnecessary use of sharp instruments and needles - Use a 'hands-free' technique where the same sharp instrument is not touched by more than one person at the same time. - Avoid hand-to-hand passing of sharp instruments during an operation. - Staff must ensure that they are aware of their 'Sharps Policy' and the action to be taken in the event of a sharps injury - Sharps containers must be properly assembled; The date and time that the container was initial use must be recorded, Once in use, the container has an expiry date of three months if not two-thirds full by then, it must be sealed and discarded and using a new container. - Sharps containers must never be filled above the fill line. - Must never insert your hand into a container to retrieve a sharp, use the flat of their hand to forcefully close a container that is over-filled. - Where sharps are used at the bedside, should be disposed and not left on the patient's bed, bedside table or locker or discarded into the domestic or clinical waste bin. - Sharps must never be passed by hand. - Needles and syringes must not be disassembled after use. - Needles must not be re-sheathed after use. - Compliance with the use of safety devices must be monitored and audited, and additional staff training organized where appropriate. - **3.4.5 Cough and Sneeze Etiquette** - Droplets from coughs and sneezes can travel up to 2 metres, these simple steps can help to reduce the spread of respiratory infectious diseases. - If you have symptoms of acute respiratory infection should practice cough etiquette (Cover your mouth and nose with a tissue when coughing or sneezing and dispose of the tissue immediately, if you do not have a tissue, sneeze into your elbow rather than your hands). - Where possible, close contact with people suffering from acute respiratory infections should be avoided. - Only when you are sick should you wear a face mask when out in public to prevent infecting others around you. - Wash your hands with soap and water immediately after coughing or sneezing. - **4 Sterilization and disinfection** - **4.1 Definitions.** - **Sanitizer:** A chemical agent typically used on food-handling equipment and eating utensils to reduce bacterial numbers. Bacteriostatic agent: An agent which can be inhibits the growth of bacteria. - **Bactericide:** An agent which can be kills bacteria. - **Viricide:** An agent which can be inactivates viruses. - **Fungicide:** An agent which can be kills fungi. - **4.2 Methods of sterilization and disinfection** - Methods of sterilization and disinfection include physical methods (heat - radiation - filtration) and chemical methods - **4.2.1 Heat** - Two types of physical heat are used in sterilization and disinfection (moist and dry heat). - **4.2.1.1 Dry heat** - **flaming:** Bunsen burner used for loops - knives - blades - **hot air oven:** Hot air oven is used to sterilize materials which can withstand high temperatures, which sterilize on 160°C for 2 hours or 170°C for 1 hour, or 180°C for 30 minutes. Oven should be fitted with a fan to provide air circulation throughout it, a temperature indicator, a control thermostat and timer, open mesh shelving and adequate wall insulation. Hot air oven is used to sterilize Glassware like petri dishes, flasks and test tubes; surgical instruments like forceps - **Incineration:** Used for the sterilization and disposal of contaminated materials such as pathological waste materials. - **4.2.1.2 Moist heat** - Moist heat kills microorganisms by denaturation and coagulation of proteins. Includes, Less than 100°C (e.g. Pasteurization), On 100 °C. (Boiling) and More than 100 °C (Autoclaving) - **4.2.1.3 Autoclave** - Autoclave is the standard method of sterilization, the principle is, when the water is boiled in a closed container, the steam condenses, which leads to an increase in pressure, that increase in pressure leads to an increase in the boiling temperature, from 100° C to 121° C if increasing it 15 ppsi above normal atmospheric, and this temperature is the most common used for 15 - 20 min. - Autoclave particularly useful for materials which cannot withstand the higher temperature of hot air oven, and used for all materials that are water containing, and not liable to be damaged by the autoclave such as culture media and other laboratory supplies, rubber material, gowns, cotton etc... - **4.2.1.4 Procedure** - Sufficient water is put in the cylinder, and the autoclave is heated. - The lid tight closed with the air tap open and adjusted the safety valve to the required pressure. - The steam-air mixture is allowed to escape freely till all the air has been displaced. - The discharge tap closed. - The steam pressure rises inside and when it reaches the desired set level (15 psi), the sterilize period (15 - 20 minutes) is calculated. - When the sterilize period is over, the autoclave is turned off and allowed it to cool, until the inside pressure reaches the atmospheric pressure - The air tap is opened slowly and air is allowed to enter the autoclave. - The lid is opened and takes out the sterilized articles. - **Advantages of autoclave** - Temperature more than 100 can destroy all microbes and spores - Condensation of steam generates extra heat - Condensation of steam allows the heat to penetrate the items - **4.2.2 Radiation** - It causes breakdown of DNA of microorganisms. It can destroy spores and vegetative form of microorganisms, - **Ionizing radiations:** have high penetrating power and include X-rays and gamma rays which used for plastics disposable, such as plastic syringes, gloves, specimen containers, plastic petri dishes and catheters, Catgut sutures and some foodstuffs. - **Nonionizing radiation:** do not have penetrated power to glass and water. It is including ultraviolet (UV) and infrared radiations. Used for sterilize of clean surfaces in operating theatres, microbiological safety cabinets. workers exposed to it must be protected and must be certain that the UV lamps are off when the areas are in use, because UV light can cause skin and eye damage - **4.2.3 Filtration** - Filtration is a mechanical method used for sterilize fluids which are damage by any type of heat e.g. serum, plasma, vaccines, antibiotics and hormones. - **4.2.4 Chemical agents** - **A. Agents that damage cell membrane such as phenolic compounds and alcohols.** - **B. Agents that denature proteins such as acids, alkalis and alcohols** - **C. Agents that change functional groups of proteins and nucleic acids such as Alkylating agents: Aldehydes, Formaldehyde, Glutaraldehyde e.g. Ethylene oxide.** - **5 Examples of diseases that caused by microorganisms** - **5.1 Bacterial disease** - **5.1.1 Urinary tract infection (UTI) caused by bacteria** - The commonest agents are pseudomonas aeroginosa, Neisseria gonorrhoeae, Mycobacterium tuberculosis, salmonella sp. and Escherichia coli - **5.1.2 Meningitis** - The commonest agents are Neisseria meningitides, Mycobacterium tuberculosis, haemophilus influenza and Streptococcus pneumonia - **5.1.3 Tonsillitis** - The commonest agents are Corynebacterium diphtheria, and streptococcus sp. - **5.1.4 Abscesses** - The commonest agent is Staphylococcus aureus - **5.1.5 Puerperal fever** - The commonest agents are Staphylococcus aureus, pseudomonas aeroginosa, streptococcus sp. vibrio cholerae, Escherichia coli - **5.1.6 Pneumonia** - The commonest agents are Pneumococci - **5.1.7 Enteric Fever:** - The commonest agents are Salmonella typhi and Salmonella para typhi - **5.2 Fungal diseases** - **5.2.1 Urinary tract infection (UTI) caused by yeast** - Causative agent: Candida sp. - **5.2.2 Mycotoxicosis** - Mycotoxicosis is the diseases that result from ingestion of food that contains mycotoxins, where many fungi produce poisonous substances called mycotoxins that can cause acute or, chronic intoxication and organ damage. - The commonest agents Aspergillus flavus produce aflatoxins which cause hepatotoxic and hepatic carcinoma - **5.2.3 Dermatophytes or "ringworm"** - The commonest agents are Trichophyton sp., Microsporum canis and Blastomyces dermatitidis - **5.3 Viruses diseases** - **5.3.1 Hepatitis** - The commonest agents are HAV, HCV and HBV - **5.3.2 Respiratory diseases** - The commonest agents are Influenza viruses and recently Covid 19.