Bacteriology General 823.docx PDF

General #### Introduction: - Microbiology is the study of microorganisms. - Difference between microorganisms: Bacteria ➡ prokaryotes - It is a study we encounter in our everyday life: There are 100 million times as many bacteria in the ocean as there are stars in...

General #### Introduction: - Microbiology is the study of microorganisms. - Difference between microorganisms: Bacteria ➡ prokaryotes - It is a study we encounter in our everyday life: There are 100 million times as many bacteria in the ocean as there are stars in the known universe. Humans also have an intimate relationship with MO: more than 90% of our cells are microbes! The number of genes contained within the gut flora outnumbers that contained in our genome. Furthermore 8% of our DNA is derived from the remnants of viral genome. - Microorganisms included are bacteria, fungi, parasites and viruses (which are the only non-cellular organisms). All of these need to be viewed on special microscopy except for some parasites that are macroscopic such as: taeniea solium #### Infection vs. disease: - Example: 2 people acquired the common cold virus: 1. The first person has a cold and thus has a **Symptomatic disease.** 2. The second person is infected but with no manifestations thus he has a **Subclinical infection**. #### Characteristics of MO: 1. **Continuity**: MO can adapt to a variety of environments that include external sources such as soil, water and organic matter etc\... In doing so the bacteria ensure their survival and enhance the possibility of transmission. By producing asymptomatic infection MO enhance the possibility of transmission from one person to another **susceptible person.** 2. **Infectious dose**: Amount of microorganisms that have ability to produce disease. It is primary and varies between types of bacteria. ##### The same MO can cause different pathogenesis according to: - Geographic area - Age group - Season ##### A MO relationship with specific pathogenesis can be described by any of these 3 terms: - **Endemic:** a disease that exist permanently in a region or population. Example: Malaria in Africa - **Epidemic:** An outbreak of disease that attacks many peoples at about the same time and may spread through one or several communities (coming from outside), also an endemic disease may become epidemic when it covers a large population. - **Pandemic:** When an epidemic spreads throughout the world. 1.1- Shapes and colonies ------------------------ ### Introduction: #### What is a bacterium? #### What is the importance of knowing the bacterial size? #### Criterion to specify living organisms? - They have to multiply - They have to produce their own energy (either by themselves or picked up by the host cells) #### What is the difference between eukaryotes and prokaryotes? -- -- -- -- -- -- - **Targeting the Antibiotic:** the difference of the sedimentation coefficient between those two can help targeting the antibiotic against bacterial ribosome only and thus will only affect bacterial protein synthesis without damaging the host\'s cells. - **Peptidoglycan layer targeting:** this structure is unique to bacteria, other prokaryotes ex: plants have their own cell wall but is made of cellulose rather than peptidoglycan; this help target this peptidoglycan wall to destruct the bacteria without harming the host. ### Bacterial Shapes: - Rod-shaped bacteria are called **bacilli** (singular: bacillus), e.g., Bacillus anthracis, which causes the disease anthrax. - Spherical bacteria are called **cocci** (singular: coccus), e.g., pneumonia is caused by Streptococcus pneumonia. - Then there are spiral bacteria, called **spirilla** (singular: spirillum), e.g. treponema pallidum that causes syphilis - comma-shaped ones, called **vibrios** (singular: vibrio) - We also have polymorphic bacteria named **coccobacilli,** i.e. it changes its form during its life cycle, e.g. Proteus species, and pseudomonas... this is dangerous because we might think that we have bacterial combination under the microscope but in fact we only have one (false diagnosis).  - Coccobacilli sometimes appear as cocci, others as bacilli or coccobacilli. - Bacilli under the microscope can be seen as individual rods or palisades arrangement ( chinease arrangement). ##### Shapes of other bacteria: - Bacillus anathracis: rectangular shape - Fusobacteria: rocket like - Pseudomonas: longer bacilli ### Arrangement and Colonies: - Individual cells - Diplococcus (two cells still attached and dividing) - Tetrad (typical for staphylococci, 4 attached dividing cells) - Sarcinae (a grape-like cluster, shows the three dimensional division) ##### Colonial morphology of other bacteria: ### Methods of bacterial identification: a. **Staining**: very general (technique discussed later) b. **DNA or RNA analysis**: highly specific and very sensitive, the presence of a certain nucleic acid sequence or specific gene is interpreted as definitive identification of an organism. c. **Antibiogram:** Tables showing how susceptible a series of organisms are to different antimicrobials. Also named susceptibility testing. Note that a contaminated culture may yield a wrong antibiogram. d. **Colonial appearance:** some bacteria appear as mucoid (not clear) e.g.: Klebsiella and pseudomonas. ### Nucleoid: ### Plasma membrane: 1. Acting as a selective barrier for permeability and transport. 2. The receptors acting as chemo attractants or chemo repulses are present on this membrane. 3. Site of lipid carriers 4. Contains DNA replication machinery 5. Site of enzymes required for biosynthesis of bacterial structure. 6. Site of lipopolysaccharide synthesis 7. Does not contain sterols 8. There are foldings of the plasma membrane named **mesosome** it is thought to be artifacts that exist due to chemical preparation preceding microscopy observation. Mesosomes are of 2 types: - **Lateral mesosome:** carries most of the membrane\'s function, such as electron transport, aerobic respiration and hydrolytic enzymes secretion (no organelles to carry out these functions). - **Septal mesosome:** where nucleoid attaches for division of the cell, if this is absent no division occurs. #### Aerobic bacteria: #### Anaerobic bacteria: ### Transport mechanisms of bacteria: -- -- -- -- -- -- -- -- C. **Cell wall:** ##### DAP: - unique to prokaryotes, it is a precursor of lysine aminoacid. - In gram negative bacteria a lipoprotein is bound to DAP. ##### Linkage between tetra amino acid chains also differs between bacterial types: - **In gram negative**: Gram negative bacteria consist of 1 peptidoglycan layer usually peptide bridges between the a.a chains within the same layer exist, between the amino end of the 3^rd^ a.a of the first set and the carboxyl end of the 4^th^ a.a of the second set. - **In gram positive:** consist of almost 200 layers. Interpeptide bond named a pentaglycine bridge cross links parallel amino acid chains within the same layer. While peptide bridges cross link occurs between different layers in the same position mentioned above. #### Basic properties of the cell wall: 9. It gives **osmotic protection:** plasma membrane is delicate but cell wall is rigid that's why it provides stability and protects the cell from lysis 10. It provides **bacterial structure.** 11. Has a role in **cell division**. 12. Site of many **antigenic determinants** (epitope): a site on the surface of an antigen molecule to which a single antibody molecule binds. Most obvious in gram positive (outer membrane of gram negative hinders this). 13. **Primer** for its own biosynthesis 14. It is an **antiphagocytic** structure which adds on bacterial virulence. 15. It is a **mitogen**: it activates lymphocyte mitosis nonspecifically (with no antigen), it triggers the mitogen protein kinase stimulating lymphocytes mitosis and thereby assessing the immune function of the host. E.g. on mitogens: Phytohemaglutin which is a structure derived from the beans. 16. **Lack lipids and protein** except for some bacteria such as mycobacterium tuberculosis. 17. **Contains openings** for transport (more prominent in gram negative bacteria). 18. **Hydrophobic** in nature 19. **Non-selectively permeable** for transport unlike the cytoplasmic membrane. ### Flagella: - Going toward specific nutrients - Escaping dangerous structures - Important virulence factor: some normal flora motile bacteria may escape their normal niche and thus become pathogenic. - They are antigenic (antigen H). ##### Types of flagella: 20. Atrichous: no flagella (not motile) 21. Monotrichous: one flagella at one end 22. Amphitrichous: one or more flagella at each end 23. Lophotrichous: two or more flagella at one end 24. Peritrichous: flagella surrounding the cell. ### Pili: - ordinary pili - sex pili. ### Capsule: - **Capsule:** tightly bound to the bacteria (doesn\'t stain well) - **Glycocalyx:** made of polysaccharides that form fibrils with the bacterial cell and make a sort of meshwork. E.g. step. Mutants that form a meshwork in the gum trapping too many bacteria. - **Slime layer:** a polysaccharide that is completely detached from the cell wall. E.g. pseudomonas aeruginosa that trap too many bacteria especially in cystic fibrosis patients, and we have staph aureus ##### Function of capsule: 25. important for adhesion 26. Contain water which protects the bacteria against desiccation (dehydration) 27. Antiphagocytic (virulence factor) 1.3-Gram positive vs. Gram negative ----------------------------------- ### Gram positive bacteria:  ### Periplasmic space: 1. **Wall teichoic acid***:* it is covalently linked to the cell wall, not present in all gram positive bacteria 2. **Lipoteichoic acid:** also called membrane teichoic acid, it is projected from the cytoplasmic membrane crossing the peptidoglycan layer to the outside. It is found in all gram positive bacteria.it is important in the pathogenesis of certain types of disease such as strep A (that causes the sore throat). ##### Function (importance): 1. They are antigenic since they are exposed and contain proteins. 2. Help in bacterial adhesion to host\'s susceptible cells, and to each other increasing virulence (bacteria aggregated can form occlusions). 3. May also function in ions transfer (minor function) ### Gram negative bacteria: ### Outer Membrane-Lipopolysaccharide: #### Lipid A: ### Polysaccharide portion: 3. Determining whether the LPS is smooth or rough: 4. It serves as a site for antibodies\' recognition (antigenic). 5. Important in serology: the type of antibody found in serology will indicate which O antigen we have and thus the specific bacteria present. (remember that each bacterial strain has a different O antigen) ### Outer membrane openings: 1. **Porins**: it is a trimeric protein (3 units of protein) which makes an opening for the transfer of many types of solute. Remember it is size dependent (no energy is required). 2. **Lam B:** it acts as a pore receptor for Lambda Bacteriophage (a virus that infect bacteria), and is also used for sugar transfer like maltose (not glucose transfer). 3. **TSX:** it acts as a pore receptor for T6 Bacteriophage, and is also used for nucleoside or amino acids transfer. 4. **Omp A**: it acts as a pore receptor for many different types of bacteriophages. And a very important function is that it is used for genetic material transfer (sex pili receptor) that is a sexual transfer between a donor and a recipient (conjugation of sex pilis). 5. **Siderophore complex:** serve to transport irons. 6. **Ion transfer** pores. ### Other properties of the LPS: 1. The site of many enzymes such as Trans peptidase enzyme. 2. The site where we have the Penicillin Binding Proteins: there exist at least 6 PBPs some of which are structural, others are enzymatic, but all are under chromosomal control. 3. They are heat stable due to interaction between its compartments. 4. They are endogenous pyrogenic: causes fever that is produced in our system 5. They are pyogenic**:** induce pus or abscess. 6. They induce platelets aggregation which leads to thrombosis and thus septic shock. 7. They induce hypoglycemia (symptom of septic shock**)** ### Oligosaccharide (LOS) vs. Polysaccharide (LPS) 1. **Ability to change the antigenicity much quicker** than LPS because they are shorter. That is: bacteria such as Neisseria replicate in the human system and upon replication it changes sugars of the Antigen O leading to antigenicity change. This causes no formation of new antibodies due to lack of time and the antibodies produced before will not recognize the new antigen and thus will not have a protective effect. 2. **Ability of LOS to mimic many of our cellular antigens or properties.** And thus the antibodies can fight the humans\' own cells due to complementarity with LOS antigenicity. ### Septic shock: - Fever usually higher than 38C, followed by a transient period of leucopenia and then leukocytosis - low body temperature (hypothermia( - fast heart rate - rapid breathing, or more than 20 breaths per minute - noticeably lower amounts of urine - acute confusion - dizziness - severe problems breathing - bluish discoloration of the digits or lips (cyanosis( - People who are experiencing septic shock will experience the symptoms of severe sepsis, but they will also have **very low blood pressure** that doesn't respond to fluid replacement. 1. **The release of endotoxin occurs [only] when the bacteria is died**. This is the first case and it is much severe than the other one because the amounts of the LPS released in circulation are very high.it leads to a very quick sepsis. 2. **The release occurs via living gram negative bacteria (they release their own endotoxin as they colonize)**. This is the second case and the amounts of endotoxin released are less compared to the case above. This case activates the inflammatory response (because it have a higher tendency of appearing on cell surface= antigenicity). ##### coagulation pathway activated: 2. **in parallel**: constriction of arterioles and venules ### Lipoprotein: C. ### Other remarkable differences between gram positive and gram negative: 6. **Site of hydrolytic enzymes secretion** (plasma membrane enzymes): ##### Staining:  8. **Binary fission** (discussion below) 1.4-Spores & Binary fission --------------------------- A. **Spores:** ### Spore characteristics: 1. ##### Can remain in environment for years 2. **Metabolically inactive**: Their DNA is not destroyed; they have all the genetic material as the bacterial cell. But they are inactive, inert 3. **Not reproductive** but they are stable because of the different layers that cover those spores. 4. **Produced in response to nutrient limitation** or extreme conditions. 5. **Very resistant** to desiccation, to different degrees of heat; they need higher temperatures, and are resistant to different chemicals: this is why they are used in biological wars. 6. ##### Completely dehydrated ### Structure of endospore: 1. **Spore wall:** it is the innermost layer covering the DNA.it has the same composition of the peptidoglycan cell wall from which it is derived (with less water content). 2. **Cortex:** Spore cortex, is composed by peptidoglycan but it is thicker than the spore but not as compact as the cell wall. (Less bridges between the layers) 3. **Spore coat:** coat (the hardest layer to destroy in the spore), it is a Keratin like structure (protein present in hair, nails...) which is extremely resistant to all external factors so if the spore should be converted to a vegetative cell, the coat has to be destroyed (the cortex is easy to destroy) 4. **Exosporium:** the outermost layer, a thin layer that covers the ### Sporulation: ##### Steps and mechanism of sporulation:  B. **Bacterial division and Growth curve:** - *Mycobacterium tuberculosis needs 3 to 8 weeks to grow*. - *E. coli grows in 4 hours.* -- -- -- -- ### Growth curve: 1. **Lag phase**: When a microorganism is introduced into the fresh medium, it takes some time to adjust with the new environment. This phase is termed as Lag phase, in which cellular metabolism is accelerated, cells are increasing in size, but the bacteria are **not able to replicate:** growth rate is zero. 2. **Log phase**: or exponential phase: with time, the population is increasing in amount per ml. The growth rate is constant. NB: Spores are produced at the end of this phase. 3. **Stationary or plateau phase:** in the majority of cases, there are around 109 bacterial cells or CFU/ml but **growth rate is mostly zero.** 4. **Decline phase**: when the nutrients get depleted in the medium, a gradual decrease in the growth is obtained until all the bacteria die. Certain toxic products are released due to the death and breakdown of the bacteria. But the rate never reaches a zero. 1.5-Synthesis of bacterial components: -------------------------------------- ### Peptidoglycan synthesis: ### Lipopolysaccharide synthesis: - Those empty areas within the bacterial cell are known as **Bayer's junctions.**  ### Lipoprotein synthesis: - It is produced in the cytoplasm - It consists of a diglyceride thioether molecule to which are added different amino acids - It is bound to the cell wall (to the DAP of the peptidoglycan) from one side, and inserted on the outer membrane on the other side. 1.6-Growth requirements of bacteria: ------------------------------------ ### Nutrition: ##### Carbon: ##### Phosphate: ### Temperature: Bacteria ##### Eubactria Archaebacteria ### Substrate: ### Ions: ### Heat-shock (HSP) and cold-shock(CSP) proteins: ### pH: - **Acidic pH (**1\ - **Facultative anaerobic:** in presence of O2 or without they can live. - **Microaerophilic** need a certain amount of O2 more O2 than anaerobic bacteria. Very close to the facultative anaerobes 1.7-Genetic material of bacteria: --------------------------------- - **Chromosomal gene** which is responsible for all the bacterial functions. ### Means for the transfer of genetic material: #### Phages: ##### There are 2 different types of phages: 1. **Lytic phages** which cause lytic infections. 2. **Temperate phages** which cause lysogenic infections. #### Transposons: #### Plasmids: - Some of these plasmids are **"conjugative"** which means they can be transferred. They have genes that allow their transfer. - Other plasmids are **"sedentary"** and cannot be transferred by whatever means we do, but they can give some virulence properties to the bacterium itself. B. **Mechanisms for genetic material transfer:** ### Conjugation: -- ----------------------- -- **\|** P a g e **49** -- ----------------------- -- ### Transduction: #### Lytic bacteriophages:  **\|** P a g e **50** #### Lysogenic temperate phages: - At this moment, in the presence of a triggering element, we will have the multiplication of the phages (production of copies) and lysis of the cell and the phages will be released as **temperate bacteriophages**. ### Transposition: ##### We have 2 types of transposons: - **Insertion sequences**: these are small replicon genes (few base pairs) that are flanked by inverted sequences. - **composite/complicated transposon:** it confers the same structure as the simple transposon but extra genes coding for antimicrobial resistance are also present with the transposon coding genes and the flanking sequences. ##### Transposons don't multiply by themselves. 3. The transfer will be much more severe. 4. The resistance to antibiotics can cover many species of bacteria. It may not stay within the same population since it has gone outside the bacterial chromosome. #### How can transposons jump to phages? ### Transformation: - The end product is the uptake of that piece of DNA.  Energy production: ================== - In aerobic bacteria: glucose is utilized by **glycolysis** - In anaerobic bacteria: **fermentation** occurs in the absence of oxygen. (Not an alcoholic fermentation: (In yeasts and fungi we have alcoholic fermentation). #### What is glycolysis? ##### Functions of the TCA cycle Krebs cycle: - The production of NADH^+^H^+^ and FADH2 for electron transport. - The production and destruction of amino acids respectively called anabolism and catabolism. The TCA cycle is amphibolic, allowing production of amino acids and derivatives of amino acids. #### Pentose Phosphate Pathway #### What is glucose fermentation? Production of spheroplasts, protoplasts and L-form: =================================================== - **Protoplast** in Gram + : generally, they lose all the cell wall but sometimes, they can retain a small fragment. - **Spheroplast** in Gram -: in most cases, they will retain a small fragment of the cell wall, because it is inside the outer membrane. ### L-forms Microscope types ================ -- -- -- -- B. **Staining techniques:** #### Gram staining: ##### Gram staining steps: 1. We have to add our specimen on the slide by the bacteriological loop The colorants are liquid, so whenever I wash, thee bacteria will go. For that reason, we should do heat fix step 2. Heat fix; fix the bacteria on the slide 3. Add the first basic stain: crystal violet or gentian violet. All the 4. Fix the dye to the bacteria by iodine (called mordant or lugol) 5. Decolorization: by alcohol this is the step during it all the CRAM -- will lose their color and be transparent because their peptidoglycan is very thin but CRAM + will retain the crystal violet. Between those steps, there is steps of washing to eliminate excess of colorant during it we use water to wash. 6. The last step is the counterstain where we use fuchsin : (it's pink to red in color). When we add it the CRAM- will be stained pink, but the Gram+ remain purple. #### Acid-fast staining:  Media preparation: ================== #### Broth medium (or liquid medium( #### Solid medium (or Petri dish(  ##### Agar: - It comes from seaweed. - It is a solidifying agent. - It is not affected by bacteria: it is inert. That's why it is used - When agar is placed in the solid medium, it can melt at high temperatures (around 121℃ in the autoclave) and become liquid. But when returned to a temperature of around 40℃, it solidifies again. That is why it is used in all of the media. ##### Procedure: 1. We start with a sterile broth medium, and add the bacteria from a solid media. 2. If we look at the broth medium we are given, it will look turbid, meaning it contains bacteria. However, we still don't know if those bacteria are alive or dead because even bacteria that have already reached the stationary phase or the dead phase and have started to decrease in number are still present and can cause the turbidity. Bacteria might not be multiplying so they might be dead. 3. We test whether the bacterial population is still alive and multiplying by plating (putting in plate) them in the Petri dishes. 4. Now we are going to plate or streak in a culture in a medium. Media Types =========== #### Differential medium: #### Enriched medium: #### Selective medium: ##### SS (Salmonella-Shigella) Medium: - Shigella causes dysentery (bloody stools) - Salmonella and Shigella are Gram - enteric bacteria that can grow in a MacConkey medium. - In order to narrow the possibilities of the type of bacteria available, they are placed in a SS medium because only Salmonella and Shigella bacteria are capable of growing in it: the rest of Gram - enteric bacteria will not grow. - Further biochemical tests are needed to identify the bacteria as either Salmonella or Shigella. ##### Blood agar plate: - Sterilized agar, is poured into plates where it solidifies, but just before pouring it, around 5% of blood is added from the medium. - Whole red blood cells are needed for the blood agar plate. They are added later on because they would have burst in the autoclave. ##### Chocolate agar: - It used for the growth of Haemophilus influenza or Haemophilus ducreyi, or Neisseria for example. - Lysed red blood cells are needed: the red blood cells are added to the agar first, and then the mixture is put in the autoclave so the cells can burst, giving as a result the chocolate-like color. Normal flora: ============= - **Resident Flora:** These are permanent MOs that have the ability to re-establish themselves so that they always exist in their particular location. - **Transient flora:** Microorganisms that colonize people for hours to weeks but do not establish themselves permanently are called transient flora. They can cause symptomatic or asymptomatic infections**.** ##### They have different mechanism to protect us: 1. **Bacteriocin secretion**: bacteriocins are proteins or peptide toxins secreted by bacteria of normal flora strains to prevent growth of pathogenic similar outsider strains. 2. **Occupies ecological niche**: its presence in a certain area prevents the presence of a space for MO found in environment to occupy and thus prevents MOs from infecting the host. 3. **Immune system stimulation**: this occurs by secretion of antibodies that can cross-react with our antigens. 4. **They secrete nutrients**: such as vitamin k, vitamin D... that is why we can see vitamins deficiency in some people administering antibiotics. - ##### Natural or nonspecific immunity: - ##### Acquired immunity: Mechanical barriers: ==================== #### Skin: - The presence of intact normal flora on the skin can produce certain fatty and lactic acids which decrease the pH of the skin. - In fact, if somebody has acne, the dermatologist will give him medication or product with low pH 5.5-5.7. That low pH will not allow the invasion of pathogenic bacteria. - If the pH is high that means there is an imbalance and the fatty acids and lactic acid are not able to lower the pH, so it's that when the skin will be invaded by pathogenic bacteria. - Normal flora secretes bacteriocin. #### Mucous layer: #### Elimination mechanical mechanisms: Chemical barriers: ================== 3.2-Second line of defense: --------------------------- 1. Monocytes (blood) 2. Kupffer cells (live) 3. Mesangial phagocytes (kidneys) 4. Alveolar macrophages (lungs) 5. Histiocytes (connective tissue) 6. Microglial cells (brain) 7. Splenic macrophages (spleen) 8. Lymph nodes (central role) resident and recirculating 9. Osteoclasts (bones) Polymorphonuclear cells ======================= - **Neutrophils**: lobulated nucleus with short life span, first cell at site of injury or infection. - **Basophils**: secrete chemicals that mediate inflammation and allergic response, bean shaped nucleus. - **Eosinophils**: destroy **parasitic** invaders usually, bi-lobed nucleus ##### There are different types of granules in neutrophils: 1. **Primary** or azurophilic granules are present in all granulocytes and contain myeloperoxidase which creates anti-bacterial compounds, acid hydrolases and defensins. 2. **Specific** or heterophilic granules are the most numerous type and contain complement activators and enzymes 3. **Tertiary** granules are either phosphatases or metalloproteinase with the later aiding movement through connective tissue. #### Primary granules: a. Large amount of **myeloperoxidase** b. **Hydrolases** c. **Cathepsins G, B and D** d. **Defensins** e. **BPI** f. **Cationic proteins** g. Small amounts of **lysozyme** #### Specific granules: a. Large amount of **lysozyme** b. **Lactoferrin**: substance that plays an important role in the transport of iron ions (Fe). It is antibacterial because it takes the iron off from the bacterial cell (even in the presence of siderophores, bacteria will be destroyed) c. **Alkaline phosphatase** (detoxifying enzyme) d. NADPH **oxidase** e. **Collagenases** f. **Histaminases** (from the mast cells). ##### Properties of the polymorphic nuclear cells: - They have a **short life span.** - They don\'t have mitochondria so they can work under - They mostly depend on the **glycolysis** for the production of energy and survival. ##### How do polymorphs cause the destruction of the bacteria ? ##### Respiratory or metabolic burst: - The hydrogen peroxide can also be converted into **singlet oxygen**, that is also toxic. - **In other cases**, in the presence of myeloperoxidase (the primary granules) and chloride ions, the hydrogen will be converted into a hypochlorous ion (OCl^-^) which can be converted into singlet oxygen that is toxic too.  ##### Another important function of the polymorphs is the destruction of the deep abscess: #### Phagocytosis by polymorphs: #### Acute inflammation: #### Cellular phase:  +-----------------------------------+-----------------------------------+ | | - - | +-----------------------------------+-----------------------------------+ | | | +-----------------------------------+-----------------------------------+ | | | +-----------------------------------+-----------------------------------+ #### Vascular phase: - In the vascular phase, small blood vessels adjacent to the injury dilate **(vasodilatation)** and blood flow to the area increases. - The endothelial cells initially swell, then contract to increase the space between them, thereby **increasing the permeability of the vascular barrier** which causes erythema (redness). This process is regulated by chemical mediators. - **Exudation of fluid** leads to a net loss of fluid containing neutrophils from the vascular space into the interstitial space, resulting in edema and in recruiting more neutrophils. The formation of increased tissue fluid acts as a medium for which inflammatory proteins (such as complement and immunoglobulins) can migrate through. It may also help to remove pathogens and cell debris in the area through lymphatic drainage**.**  #### Following the process of acute inflammation, there are several possible results: 1. **Complete resolution** -- with total repair and destruction of the insult. 2. **Fibrosis and scar formation** -- occurs in cases of significant inflammation: if it has not been possible to destroy the infectious agents or to remove all of the products that have accumulated at the site completely, they are walled off from the surrounding tissue in granulomatous tissue. A granuloma is formed when macrophages and lymphocytes accumulate around material that has not been eliminated, together with epithelia cells and giant cells (perhaps derived from macrophages) that appear later, to form a ball of cell 3. **Chronic inflammation** -- from a persisting insult, occurs if neutrophil were unable to kill the pathogen. 4. **Formation of an abscess**: due to dead microbes and cells. #### Detection of Acute infection: How can an infection harm our body? =================================== ### Direct: ##### Through toxins: a. Endotoxin which causes clotting and thus hypo perfusion of organ lading to sepsis and tissue injury. b. Exotoxin which may cause tissue damage. ### Indirect: a. **activation of PMN and macrophages:** Polymorphs secrete enzymes to produce the tissue damage. b. **T-cell activation:** which increases the levels of the cytokine: Interferon gamma that functions in inducing macrophages and thus causing continues cell damage. c. **B-cell activation**: producing antibodies**.** Pathogenesis: ============= - The steps by which the bacterium works until it produces the disease is called **pathogenesis**. - Transmission is necessary for the microorganism to persist. When there is transmission, there is infection with or without disease. ##### There are 3 types of bacteria that we encounter in our life: - Cause disease under some circumstances (sometime can be members of our normal flora) - When we say opportunist it means that they can cause diseases. Usually when you are immune suppressed. - One of the easiest ways by which you can disturb your normal flora is the intake of antibiotics - **The worst is when there is a nosocomial infection:** - You have a patient with already immune suppressed in an environment of the hospital which is full of many types of bacteria and those bacteria usually are multi- drugs resistant. - Burn patient in the hospital which is the best area for pseudomonas, they can go there without any effort and stay in this burn area. - Introducing pseudomonas with the respirator (to the lungs) or with a lumbar puncture. - In addition to pseudomonas we can talk about the Candida albicans which is a fungus #### Roots of transmission: 1. **Fecal/oral transmission:** MO present in stool can be transmitted either directly (hand shaking) or indirectly (ingesting contaminated food or drinking contaminated water) A study showed that not washing our food is better than washing with water which provides a better environment for bacterial growth so we better use proper disinfectants to overcome this. 2. **Inhalation:** A very difficult mode of transmission, MO can be persistent on fomites for certain duration. It is hard to control such an infection because we don\'t know what bacteria are present around us; example: [mycobacterium tuberculosis]. 3. **Biological wars:** The easiest way is to throw doses of MO which can be inhaled and cause diseases. These genetically engineered MO have increased virulence properties. ex: Bacillus anthraces. 4. **Blood products:** transfusions, dialysis 5. **Sexual Transmission (STD):** hard to control, usually through campaigns because we cannot forbid people from having sexual relations. Also loyalty (no promiscuity) is a control measure. Most STDs are asymptomatic (mostly in females). 6. **Direct Contact:** some of which are due to direct contact with animals such as: [Malta fever] or human contact or fomites. 7. ##### Congenital transmission: - **In utero :**fetus still in womb, acquired via blood transfusion especially. - **During delivery**: bay passing through infected birth canal.it can be through contact, inhalation or skin lesions. Ex: herpes simplex virus 2. (type 2 in genital area, type 1 is oral) 8. ##### Transmission from animals to humans: 9. **Opportunists/Nosocomial Transmission:** discussed above 10. **Vector born:** vectors are like mosquitos or any others that can transmit microorganisms from a certain reservoir to humans. The reservoir can be animals, in such a situation a vector can transmit the microorganism. For example: plague (طاعون) can be transmitted directly from a bite of an infected rat or from a vector's bite. #### What will indicate whether there will have an infection or a disease? - The transmission depends on the **root of exposure:** that is the way by which the bacteria are transmitted. If the bacteria are transmitted by contact for example, then we won\'t get infected if we swallow it. - **the infectious dose:** which is the amount of the bacteria needed in order to cause an infection, plays a major role in transmission. - **Age** - **Immune status** - **Genetic predisposition** - **Gender** #### Stages of pathogenesis: ##### Incubation period: - *common cold: 1 or 2 days* - *Hepatitis B: 180 days* - *Mycobacterium leprae: 40 years* 2. ##### Illness 3. **Convalescence stage:** Koch\'s Postulates: =================== 1. Microorganism must be present in every case of the disease. Let's say I have 100 cases of a sore throat (pharyngitis), I should have the same microorganism in all cases. 2. Organism must be grown in pure culture from disease hosts. This means all have the same manifestations. For example, let suppose it's due to Streptococcus pyogenes, I should find strep. pyogenes in all and should be able to do culture of course in vitro. 3. Produce the same disease from the pure culture. Means if I could prepare a pure culture in a test tube (broth medium), and if I give or inoculate those bacteria into susceptible laboratory animal models (pigs, ducks, goose, mouse, hamster or monkeys depending on the type of animal model), they should develop the same type of disease as in the first case. 4. Organism recovered from experimentally infected hosts. Means from these animals I should be able again to recover the same type of bacteria or microorganism. Molecular Postulates ==================== - *we have many types of bacteria which cannot be grown [in vitro] like Mycobacterium leprae and Treponema pallidum.* - *Also there are other bacteria which cannot infect laboratory animals.* 1. Virulence gene or its product must be present: 2. Virulence gene must transform a non-pathogen to a pathogen: So it is that gene that makes the strain of bacteria pathogenic, if it is not present it will be not pathogenic 3. Virulence gene must be expressed during disease process: For different bacteria we have different virulence factors which will be expressed (we have talk about them when we talked about the structure of the bacteria), the turn back of the virulence gene will make the non-pathogenic strain virulent. 4. Antibodies against gene products, are protective: Antibodies against gene product like antigen or proteins or whatever is the antigen, are protective. Establishing an infection: ========================== #### Encounter #### Adherence #### Colonization - Competition with the normal flora (for nutrients) - They should resist natural barriers and defense mechanisms: - Bile - Stomach acidity - Peristalsis - Skin secretions - Compete with host for iron via the production of siderophore which is one of the virulent factors - IgA (mucosal antobodies): #### Invasion of tissues: - Some invade the tissues **in between the junctions** of the cells, they don't penetrate the cell itself. So they cross a certain tissue layer and go into deeper areas. - In other cases they **pass into the cell** and multiply within that cell, they affect it someway. - In other cases they **transit through the cell** to go to deeper layers.  - The phagocytic cell will destroy the bacteria - The bacterial cell isn't affected by the phagocyte but uses it as a vehicle and a place to multiply. That phenomenon allows bacteria to spread into more and more cells continuously. In many cases they quit the macrophages then go **directly** from cell to cell continuously without being exposed to the external environment. - The whole process will stop = immune response or antibodies will be able to get rid of the bacteria after the invasion. - Bacteria that have invaded the blood multiply in the blood to higher levels; in that case it's not a pure or an innocent bacteremia anymore, it becomes a **Septicemia**. Once we have **invasion of the blood+ multiplication of bacteria to larger numbers**, and because we have perfusion of the blood in all the organs, the bacteria can be spread to all the other organs of the body. Now the organs that were spared and not affected before (ex: liver, pancreas, brain\...) will be infected. ##### M cells invasion: - There is no formation of a phagosome, the bacteria stays in the cytosol of the macrophage. - There is no phagolysosomal fusion - Bacteria is resistant to the activity of the cytoplasmic granules. #### Avoid the host defenses - There is one situation where the host cell surface contains molecules that bind complement regulatory proteins (CRP). When that binding occurs and the C3b attaches to host cell surface, the complement regulatory proteins inactivate it. - In other situations, the bacterial surface contains molecules that bind complement regulatory proteins. #### Survival Srategies Within Phagocytes: - Escape the phagosome - Block lysosome infusion - Surviving within the lysosomes by being resistant to the granules #### Avoiding Antibodies 3.4-Bacterial Toxicity: ----------------------- - **Endotoxin** which are an integral part of the gram- bacteria and work whether it is released as a fragment or as part of the bacteria cell (in both cases they have the same activity) - **Exotoxin** which are released by the bacteria in gram + and -- Exotoxins ========= - **Enterotoxin**: exotoxins causing food poisoning and affecting the intestinal tract (ex: diarrhea, vomiting, etc\...) - **Other type** doesn't necessarily affect the intsestinal tract but has many other activities like breaking down hyaluronic acid, collagen, destroy white or red blood cells, platelets\... ##### The activity of exotoxins depends on the type of the bacteria. - be acquired in certain numbers - colonize certain cells in our intestinal tract - produce and release toxin ##### We have different types of food poisoning: - vomiting with a little diarrhea. - only diarrhea without vomiting. - Fever: some types of food poisoning induce fever, others do not. #### Properties of exotoxins: 1. **They are secreted by living cells**. The cell must be alive to multiply and code for the production of the exotoxins; [unlike] endotoxins that have 2 varieties: the lipopolysaccharide may be released from dead bacteria or remain as an integral part of an alive bacteria, in both cases the endotoxin will have similar toxicity effects. 2. **Can be produced from gram positive or gram negative** bacteria[; unlike] lipopolysaccharide which is only found in gram negative bacteria. 3. Structure: **most exotoxins are polypeptide** [but] endotoxins are lipopolysaccharide. So exotoxins are very good antigens (the strongest of antigens) to induce the production of antibodies. Lipopolysaccharides are also antigenic but at a very low level. 4. Most exotoxins are composed of 2 portions linked by disulfide bonds: 5. They can be converted to toxoids 6. Heat labile in most cases 7. Bind to specific receptors (unlike endotoxins) 8. Most importantly, they are active in microgram amounts (endotoxins are active when present in larger amounts, maybe 100s of micrograms). 9. **Exotoxins are coded mostly by extrachromosomal genes** especially when the disease is toxin mediated and not caused by the bacteria itself (endotoxins are usually coded by the bacterial chromosome). 10. They generally **don't** induce fever (endotoxins are pyrogenic). Membrane damaging toxins: ========================= #### Hemolysins: 2. #### Phospholipase 3. **Hyaluronidase** #### Gas gangrene #### Super-antigens: - Super-antigens differ from antigens in that they can hyper- stimulate the immune system. - Many of the super-antigens can lead to shock=\ organ failure and circulatory collapse. Toxic Shock Syndrome Toxin (TSST): ================================== Endotoxins: LPS =============== - Don\'t bind to specific receptors on cells, they need a mediator protein to attach them to their target immune cells especially monocytes and macrophages with the induction of cytokines and interleukin1 (IL1). - Are coded by the bacterial chromosomes. - Are active when present in large amounts. - Are usually pyrogenic due to the production of IL1. - Can be active either when released or as part of the bacteria. - It\'s very important to note that the pathophysiologic effect of the endotoxin in the system is the same irrespective of the type of bacteria. ##### There are many things that characterize an endotoxic shock: 1. The first characteristic is the **fever**. In parallel with the fever there is early **leucopenia** which means that directly after the infection, there is a decrease in the number of leucocytes. 2. Early leucopenia is a transient period followed by a period of **leukocytosis** (increase in the number of leucocytes) especially in the case of superinfections where a person is infected by more than one type of bacteria which makes the disease much more severe. A property of lipopolysaccharides is that they induce hypoglycemia. 3. Another important characteristic is the hypotension which will lead to vascular collapse and the endotoxic shock. Due to hypotension, some of the most important organs in our system (vital organs) like the brain, heart, lungs and kidneys will receive less blood, so we say that these organs will not have proper perfusion. The hypotension starts with the constriction of the arterioles and venules which will be compensated by peripheral vasodilation. This will lead to increased vascular permeability which will cause a decrease in the venous return, so the cardiac output decreases till we reach a stage of stagnation in the peripheral circulation. 4. In parallel to all of this is something we call the **DIC (disseminated intravascular coagulation)** which is a condition in which blood clots form throughout the body causing the blockage of certain vessels which could lead to thrombosis. There are many factors that participate in this coagulation: - Lipopolysaccharide that activates the alternate complement pathway will result in a decrease in in the levels of many components of the complement and it can allow the platelet aggregation. - In parallel, the lipopolysaccharide can activate the clotting system, which activates fibrinogen to produce fibrin because it acts on Hageman Factor or Factor XII which acts first in the clotting system - At the same time, it can activate plasminogen into plasmin, and the latter is a proteolytic that will break down fibrin into fibrin split products - DIC is not only produced as the result of the presence of endotoxin for ex a gram + bacteria that do not have endotoxin but we say a disseminated intravascular coagulation and other factors in viral diseases these are DIC irrespective of the endotoxin) ##### +Review page 26 for more info on septic shock Bactericidal and bacteriostatic: ================================ B. MIC & MBC: ========== - **MIC**= minimal inhibitory concentration. - **MBC**= minimal bactericidal concentration. - *Not all antibiotics are able to cross the blood brain barrier even if this barrier became more impermeable. Some will cross, others not.* - *Meninges are a close small system not like urine. If I have a meningitis and want to take the same drug that treats a urinary tract infection, the dose that I have to take for meningitis is less than the urinary infection because we have urination.* - *It's easier for the antibiotics that inhibit the cell wall synthesis to cross the wall of a gram+ than the wall of gram- (the antibiotic acts on peptidoglycan).* 4.1-Antibiotic classification: ------------------------------ - It can inhibit **cell wall synthesis**. (Only bacteria have cell wall, humans don't have cell wall, so there is a selective toxicity to the bacteria.) - They can **destroy Cell (cytoplasmic) membrane** function - **Inhibits protein synthesis** (it can cause a problem) - **Inhibits nucleic acid synthesis**: several antibiotics inhibit the nucleic acid synthesis of the bacteria, but have side effects and cross-reactivity with the host cells. - Antibiotics that interfere at a certain stage in the **Metabolic pathways** of the bacteria Antibiotics that act by cell wall synthesis =========================================== #### Penicillin: - **Structure**:6-aminopencillanic acid(intact), under exposure to beta lactamase it becomes 6-aminopencilloic acid which acts as a sensitizing hapten (antigenic determinant) but with no antibacterial affect. - **Target bacteria categories**: a. High activity against gram +, spirochetes with high sensitivity to lactamase. b. Lower activity against gram + with low sensitivity against lactamase. c. High activity against both gram + and gram - with low sensitivity against lactamase. d. Applicable for oral intake - **Target bacteria:** gram positive bacteria especially bacilli and spirochetes nowadays. - **Sensitivity:** highly sensitive to beta lactamase. - **Route of administration:** parenteral - **Extra notes:** it falls in the 1^st^ category above. like all beta lactams it cannot affect intra-cellular bacteria: chlamydia and rickettsia, nor mycoplasma bacteria**.** 1^st^ drug of choice for streptococcal infection (11 or 12 injections each 10 days for prophylaxis.) - **Target bacteria:** lower activity against gram (+) - **Sensitivity:** low sensitivity, more resistant - **Route of administration:** parenteral - **Extra notes:** it falls in the second category. - **Target bacteria:** high activity against gram+ and gram- - **Sensitivity:** highly sensitive. - **Route of administration:** parenteral - **Extra notes:** falls into the third category. - **Target bacteria:** gram + and gram - - **Sensitivity:** less sensitivity to beta lactam and - **Route of administration:** oral - **Extra notes:** falls into the fourth category, can be administered orally because unlike the other beta lactams they tolerate digestive enzymes. ##### Extra notes about Penicillin: A. The patient should be tested for Penicillin Allergy, and this better happen in the hospital to minimize the consequences. (a simple skin test). B. If the patient is allergic, he can manifest one of the reactions: - **Hyper-sensitivity:** Immediate, mediated by IgE. Manifested with skin redness or urticarial. It occurs due to **sensitizing** (a progressive response amplification due to re-exposure to a stimulus). The first exposure (which is basically forbidden) occurs due to food containing antibiotics, cosmetics etc... - **Anaphylactic Shock:** takes a couple of days, it is a serum sickness: an allergic reaction characterized by skin rashes, fever and joint stiffness. - **MRSA: methicillin resistant staph. aureus** - **MRSE: methicillin resistant staph. Epidermis** 2. **Clavulanic Acid (*sulbactam)*** - **Target bacteria:** No anti-bacterial effect alone. - **Sensitivity:** highly resistance - **Route of administration:** parenteral and oral. - **Extra notes:** used in combination with other beta- lactams. #### Cephalosporin: - **Structure:**7-aminocephalo sporanic acid (do not study) - **Target bacteria:** both gram positive and gram- negative - **Mechanism:** similar to penicillin - **Extra notes:** compared to penicillin they are more resistant to some beta-lactamases produced by gram -- and staphylococci. a. **First generation cephalosporin:** - **Target bacteria:** high activity against gram + cocci, MRSA except enterococci. Moderate activity against gram -- bacteria. - **Extra notes:** neither penetrate the CNS nor are the drug of choice for any disease. -- -- -- -- b. **Second generation:** - **Target bacteria:** all of those of the first generation but with extended activity against gram -- bacilli except for **pseudomonas aeruginosa.** -- -- -- -- c. **Third generation:** - **Target bacteria:** reduced activity against gram positive, expanded activity against gram negative including Pseudomonas and MRSC. - **Extra notes:** ability to cross the CNS and appear in spinal fluid to treat meningitis. -- -- -- -- d. **Fourth generation:** - **Target bacteria:** activity against pseudomonas, greater activity against MRSC and streptococci. #### Vancomycin - **Structure:** glycol-peptide, poorly absorbed by intestine bactericidal. - **Target bacteria:** MRSC, staphylococci some bacilli and some clostridium - **Mechanism:** inhibits early stages in cell wall synthesis through inhibiting a.a cross linkage. - **Route of administration**: parenteral - **Extra notes:** - it has a special valuable effect against endocarditis. - it consists of big molecules that cannot cross the outer layer of gram (--), (bacterial resistance mechanism) - susceptible to efflux mechanism: rejected by bacteria - also bacteria with a fifth a.a other than D- alanine can be resistant to it because it only recognizes the end D-Alanine. 5. #### Bacitracin: - **Structure:** polypeptide, derived from bacillus sabtillus, bactericidal. - **Target bacteria:** gram (+) bacteria, streptococci pyogens in vitro - **Mechanism:** inhibits the undecaprenol (UND) dephosphorylation so precursors are not released. - **Route of administration:** Topic - **Extra notes:** it is highly toxic to be administered parenteral or oral. It is used in combination with polymixicins we also use it with strep A in the lab. 6. #### Isoniazid and ethionamide: - **Structure:** IND, ethinoamide - **Target bacteria:** mycobacterium tuberculosis - **Mechanism:** inhibit mycolic acid synthesis, diffuse the much non-dense lipid layer. - **Extra notes:** - used in combination with other mycobacterial agent. - isoniazid: isonictonic acid hydrazide.(IND) - diffuses tissue fluid including CSF. 7. #### Monobactam: - **Structure:** not required - **Target bacteria:** active against gram (-) only. - **Mechanism:** binds through PBP3, highly resistant to beta -lactamase - **Route of administration:** parenteral every 8 or 12 hours - **Extra notes:** - tolerated by people with allergy to penicillin. - super infections with staphylococci can occur. - **aztreonam** was the 1^st^ drug to be available. 8. #### Carbapenem: - **Structure:** not required - **Target bacteria:** broad spectrum for anaerobes**:** gram (-), gram (+) and anaerobes. used with bacteria resistant to other drugs. - **Mechanism:** long half-life like penicillin G. active against non-hospital complex infection. Highly resistant to beta-lactamase. - **Extra notes:** - Imipenem was the 1^st^ drug of this type. - sensitive to kidney hydropeptidase, so administrated with peptidase (cilastatin). - penetrates the CSF - patients allergic to penicillin may be allergic to Imipenem. 9. #### Cycloserine: - **Structure:** not a beta-lactam. Bactericidial. - **Target bacteria:** broad spectrum antibiotic, used to treat mycobacterium avium and tuberculosis. - **Mechanism:** inhibit the reaction involved in the fifth D- alanine incorporation. - **Route of administration:** oral - **Extra notes:** causes the instability of the a.a Antibiotics that Inhibit cell membrane ====================================== 1. #### Polymixicins: - **Structure:** detergent-like cyclic peptide - **Target bacteria:** gram (-) - **Mechanism:** binds to lipid A, phospholipids: phosphatidyl ethanolamine - **Route of administration:** topical - **Extra notes:** it is neurotoxic and nephrotoxic. When bond to lipids the integrity will be damaged, imbalance occurs and rapture of bacterial cell occurs. Antibiotics that Inhibit nucleic acid ===================================== 1. #### Quinolones: - **Structure:** - - **Target bacteria:** majority of gram (-), staphylococci and enterococci - **Mechanism:** inhibit the activity of DNA gyrase or topoisomerase inhibiting thus DNA replication and super coiling. - **Route of administration:** oral usually but can be administered parenteral. - **Extra notes:** - **Bactericidial/**do not reach CSF - Used as urinary anti-septic, 1^st^ drug of choice for urinary tract infection. - All quinolones are excreted by the kidney. - Bacteria can develop resistance against it. - **Side effects of quinolones:** Diarrhea, fever, nausea and cartilage destruction (so should not be used for long periods). - **Structure:** synthetic - **Target bacteria:** gram negative - **Mechanism:** target the A-subunit of gyrase - **Route of administration:** oral - **Extra notes:** the 1^st^ quinolone drug, used in urinary tract infection. - **Norflo**xacin: against gram -- and gram + - **Ciproflo**xacin: against gram -- and gram+ anaerobes - **Cino**xacin: against gram (-) - **Oflo**xacin : against gram -- and gram + anaerobes. 2. #### Rifamycin (rifampicin): - **Structure:** not required - **Target bacteria:** mycobacterium tuberculosis and MRSA - **Mechanism:** binds strongly to DNA-dependent RNA polymerase thus inhibiting RNA synthesis - **Route of administration:** oral - **Extra notes:** Bactericidal - Used for tuberculosis treatment but can also be used in severe conditions: pneumonia. - Used for prophylaxis, resistance emerge quickly. - It can bind to prosthetic devices and clear the infection. - **Side effects include:** orange skin, urine and tongue. But this is temporary. 3. #### Metronidazole: - **Structure:** not required - **Target bacteria:** it is an anti-parasitic drug but can be used for anaerobes - **Mechanism:** it should be reduced into intermediate stages in order to be active: it causes nucleic acid breakage. - **Route of administration:** oral and parenteral - **Extra notes:** used in diarrhea caused either by antibiotics or of unknown origin. Used as preoperative prophylaxis especially for abdominal pain. Anti-metabolic drugs: ===================== 1. #### Sulfonamide: - **Structure:** similar to PABA - **Target bacteria:** gram (+) and gram (-) - **Mechanism:** competitive inhibitor of PABA Utilization: inhibit dihydropetroate synthase. - **Route of administration:** oral - **Extra notes:** used for urinary tract and respiratory tract infections.it is part of **Bactrim** formation: Bactrim is formed of 5 parts sulfonamides and 1 part of trimethoprim. Bactrim is a broad spectrum antibiotic. 2. #### Trimethoprim: - **Structure:** Precursor of thymidine structure - **Target bacteria:** Broad spectrum - **Mechanism:** PABA competition, inhibit dihydrofolate synthase. - **Route of administration:** oral - **Extra notes:** Bactrim is an antibiotic in which many people, especially women develop allergy against. The allergy is characterized by vaginal itchiness due to candida albicans fungi growth in the absence (suppression) of the normal flora. 3. #### Dapsone: #### Other drugs of this category: a. **sulfamadizime,** b. **sulfamethaxole** c. **Para-amino salicylic acid** = aspirin which is used as an alternative antibiotic in multi-drug resistant tuberculosis. Drugs that inhibit protein synthesis: ===================================== #### Aminoglycosides: - **Structure:** not required - **Target bacteria:** active against Aerobic bacteria( broad spectrum for aerobic bacteria). - **Mechanism:** Usually bind to the 30S ribosomal subunit. - **Route of administration:** Parenteral - **Extra notes:** - it is bactericidial. - It is the 1^st^ protein synthesis inhibitors, usually administered with other drugs synergistically. - ***synergy:** the amplified additive effect: combination of 2 bacterial anti-biotics (or more) to produce a greater effect greater than the sum of their effect (1+1=10).* - ***mycin :** derived from the Streptomyces species* - ***micin:** derived from the microminospora species.* 1. **Gentamycin:** 2. **Tobramycin:** 3. **Kanamycin and neomycin:** 4. **Amikacin:** 5. **Netilimicin:** 6. **Spectinomycin:** 7. **Streptomycin:** - **Structure:** not required - **Target bacteria:** enterococci, tuberculosis - **Mechanism:** bind to 30S subunit, freezes initiation and mRNA misreading. - **Route of administration:** parenteral - **Extra notes:** - the oldest aminoglycoside - it is bactericidal. - It has 2 weakness points: - **It is markedly toxic for the vestibular portion of the 8th cranial nerve:** It causes vertigo, ataxia (no muscle coordination) and tinnitus (annoying voices in the ear). - **Resistance against it emerges quickly** so we have to use it with combination of other drugs. The most severe resistance is the chromosomal mediated. 1. **Gram (--) Septicemia:** septic shock, we use aminoglycosides with beta-lactam, and then we treat the toxicity and failure due to treatment. 2. **Septicemia of unknown etiology:** arising from hospital acquired infection. 3. **Bacterial endocarditis:** acute, sub-acute caused by gram (-) or gram + bacteria. We use aminoglycosides combined with penicillin. 4. **Pyelonephritis:** an infection in the kidneys with no known cause usually. The pain usually decreases during antibiotic administration but may re-occur when we stop the antibiotic (the patient is administered antibiotics for almost a life- time which is very dangerous). 5. **Post-surgical abdominal sepsis:** we use anti-anaerobe and septicemia therapy. It causes peritoneal caring. 6. **Septic shock due to extreme of age, urinary catheters and intravenous catheters.** 11. #### Tetracycline: - **Structure:** not required - **Target bacteria:** susceptible gram (-) and gram (+) - **Mechanism:** inhibiting amino-acyl t-RNA binding to the 30S subunit. - **Route of administration:** oral and parenteral. - **Extra notes:** - Poor CSF penetration it is **Bacteriostatic.** - The bacterial resistance to it is transmissible under plasmid control, and the major resistance mechanism against tetracycline is the **efflux.** - Drug of choice for some intracellular bacteria. This drug is highly abused and is used as animal-growth promoter. a. chlortetracycline b. oxytetracyclin c. doxycycline d. minocycline 12. #### Chloramphenicol: - **Structure:** not required - **Target bacteria:** no longer drug of choice - **Mechanism:** binds the 50Ssubunit of the ribosome by blocking a.a attachment to the emerging poly- peptide chain. - **Route of administration:** oral and parenteral - **Extra notes:** - It is **bacteriostatic.** - Penetrates the CSF - It has a structure similar to benzene so it is inactivated in the liver by glucouronic acid but this does not happen in children that is why if it is administered to children they will develop **gray-baby syndrome**. - It also causes bone marrow suppression. - **It used to be the drug of choice for typhoid-**fever but it is no longer used now. 13. #### Macrolides: - **Structure:** not required - **Target bacteria:** gram(+) mainly streptococci - **Mechanism:** prevents translocation and initiation complex formation by binding the 50S subunit. - **Route of administration:** oral and parenteral - **Extra notes:** - **Bacteriostatic** - The most important derivative of it is **erythromycin**: active against gram (+) showing reduced activity with less side effects. Erythromycin is the 1st penicillin G alternative. a. roxithromycin b. azethromycin: improved activity against gram (-) c. clarithromycin: improved activity against gram (+) and legionella. 14. #### Fusidic acid: - **Structure:** not required - **Target bacteria:** gram (+), MRSA - **Mechanism:** act on 30S subunit. - **Route of administration:** topical and may be oral - **Extra notes: bacteriostatic.** 15. #### Lincosamides: - **Structure:** not required - **Target bacteria:** active against gram (+) usually in bone diseases - **Mechanism:** block translocation through binding the 50S subunit. - **Route of administration:** oral - **Extra notes:** - They cure infection (osteomyelitis) through penetrating the bone. - No CSF penetration. a. Lincomycin b. Lincocin c. **Clindamycin:** is an alternative drug for staph and strep cocci. 4.2-Resistance: --------------- ##### There are several mechanisms by which MO can exhibit drug resistance: 1. Enzyme production to destroy active products 2. Micro-organisms change their permeability to drug 3. Alter the structure of an anti-biotic target. 4. Develop an altered metabolic pathway 5. Develop an enzyme with the same metabolic function but with less drug effect (competition). ##### Origin of drug resistance: - Non-multiplying bacteria - MO may lose the structure targeted by the anti-biotic through evolution - MO may infect host atsites where anti-biotics are excluded or inactive. - Chromosomal resistance: spontaneous mutation, selective advantage. - Extra chromosomal resistance: arranged form the fastest to the slowest transmission are: transposons, plasmids. ##### How person can overcome resistance: a. Combining drugs b. Maintain high levels of drug in the tissue c. Avoiding the abuse and exposure of MO to a certain valuable anti-biotic. 4.2-Miscelleneous: ------------------ #### Anti-septic vs. anti-biotic: - Chlorhexidine and other biguanides. These are used on open wounds and for bladder irrigation. - Antibacterial dye. These help to treat wounds and burns. - Peroxide and permanganate. These are often used in antiseptic mouthwashes and on open wounds. - Halogenated phenol derivative. #### What is a disinfectant?