Clinical Bacteriology 1 Midterm PDF

CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm PATHOGENESIS (HOST-MICROBE 3. Systemic infection (Generalized infection)...

CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm PATHOGENESIS (HOST-MICROBE 3. Systemic infection (Generalized infection) - microbes spread throughout the body through the INTERACTION) DEVELOPMENT OF AN blood or lymph. INFECTION AND DISEASE INFECTION AND IMMUNITY There are (3) types of systemic infections INFECTION A. Bacteremia Involves the growth and multiplication of microorganisms presence of bacteria in the blood. that cause damage to the host Organisms invade the bloodstream without Bodily invasion of pathogenic microorganisms that active multiplication reproduce, multiply, and then cause diseases through The bacteria are not multiplying or they are local cellular injury, toxin secretion, or antigen-antibody not reproducing. But, they can be detected reaction in the host. when we are going to have a culture and sensitivity (best identified). When a patient Types of Infection According to the cause is experiencing a high fever. 1. Autogenous infection Highest concentration of bacteria in the blood - caused by a microorganism from the microbiota of occurs before the fever spikes. the host. 2. Iatrogenic infection B. Septicemia - is an infection that occurs as the result of some active multiplication of the invading bacteria medical treatment or procedure. in the blood. 3. Opportunistic infection Presence of bacteria in the blood. But, - an infection that affects immunocompromised hosts only then this bacteria are multiplying but not the individuals with a normal immune Dosage of the bacteria in the blood system. plays a very important role in its 4. Nosocomial infection virulence - also known as the hospital-acquired infection. - type of infection that is acquired at a healthcare NOTE: facility Bacteremia is easily to cure compared to - Hand washing is still the cornerstone of modern septicemia. Once it exposed the bacteria to infection control programs antibiotics, it eliminates and washed out. Unlike septicemia, it takes time to eliminate. 4 common types of nosocomial infections It affects children and newborn children. If it A. Urinary tract infection is left untreated it might leads to mortality B. Lung infection C. Surgical site infection C. Pyemia D. Blood stream infection condition wherein pus-producing organisms repeatedly invade the Predisposing factors to nosocomial infections bloodstream and become localized at a. Wide variety of microbes in the hospital different parts of the body. environment Extent Of Infection b. Weakened or immune-compromised patients 1. Primary infection c. Chain of transmission (direct or indirect) - initial infection that causes the illness. i. From health workers to patients - Example is the common cold ii. From patient to patients 2. Secondary infection iii. Use of fomites - caused by opportunistic pathogens after the - Non Living things which primary infection has weakened the host’s can be use as a source or immune system. source of infection - Examples are pneumonia and bronchitis that may iv. Airborne transmission develop from a common cold. v. Vector-borne transmission 3. Latent infection (Silent phase)- - (insects) - clinically silent inside the body and causes no Types Of Infections According To Host noticeable illnesses in the host. Then severe Distribution and acute infection manifests. 1. Local infection - Example is the asymptomatic type polio infection signs and symptoms are confined in one area. 4. Mixed infection examples are the infected wounds, boils (pigsa) - caused by two or more organisms and abscesses - Example is a wound infection 2. Focal infection 5. Acute infection starts as a local infection before spreading to the - type of infection that develops and progresses other parts of the body slowly examples are tooth infection, tonsillitis, - Example is a whooping cough appendicitis, and wound infections caused by 6. Chronic infection Clostridium tetani. - an infection which develops slowly with ○ Clostridium tetani - if we ignore it, milder but longer-lasting symptoms. the bacteria itself can migrate into - Example is tuberculosis our brain, and can cause seizures. Padayon, future RMT 🔬1  CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm Routes of Infection 4. Decline period 1. Direct transmission - the period in which the signs and symptoms begin to Congenital contact – Strept.agalactiae, Neisseria subside as the host’s condition improves. gonorrhoeae and Treponema pallidum Sexual contact – N.gonnorrhoeae and T.pallidum 5. Convalescence or the period of recovery Infectious respiratory secretions or droplets – - period in which the surviving host is recuperating Strept.pyogenes and N.meningitidis towards full recovery. Hand-to-hand transmission – Rhinovirus Predisposing Factors of Diseases 2. Indirect transmission 1. Gender 6. Environment Fomites, water and arthropod vectors 2. Genetic factors 7. Lifestyle 3. Climate and weather 8. Age DISEASE 4. Nutrition 9. Occupation A specific illness or disorder that is characterized by a 5. Fatigue/stress recognizable signs and symptoms which are attributable to heredity, infection, and environment. It results when the infection produces notable changes in General Classes of Pathogenic Microorganisms the human physiology, specifically those that cause 1. True pathogen damage to the body’s organ system - these organisms are able to invade the tissues of healthy individuals through some inherent ability Classification of Infectious Diseases causing various diseases. - normally found outside 1. Communicable or contagious disease the host. - spreads from one host to another, either directly or indirectly. 2. Opportunistic pathogens - Examples are tuberculosis, herpes, flu, and - normally do not cause diseases in their natural chickenpox habitat in healthy person. 2. Non-communicable disease - They cause diseases if the host is - does not spread from one host to another. immunocompromised or if they enter a different part - caused by external microbes or by of the body. opportunistic pathogens living in the body. - Examples are Neisseria meningitidis and - Examples are tetanus and botulism Escherichia coli. Classification of Disease According to Host-microbe Relationship Occurrence 1. Symbiosis – is the association of two organisms living in 1. Sporadic disease – occurs occasionally close proximity. 2. Endemic disease – is constantly present in a particular location or population. 2. Mutualism – is a symbiotic relationship in which both 3. Epidemic disease – is a disease that affects a large organisms benefit from each other. number of people in a population within a short period of time. 3. Commensalism – is a relationship in which one 4. Pandemic disease – disease that affects populations organism benefits while there is no beneficial or harmful across large regions around the world. effect to the other. Effects of Infectious Diseases 1. Signs 4. Parasitism – is a relationship in which one organism - these are objective changes that can be measured. (parasite) benefits at the expense of its host. - Examples are fever, redness, swelling, and Terminology paralysis 1. Biofilm production - is a complex interaction between the host, indwelling 2. Symptoms device, and bacteria and is a key component in - are subjective indications of the disease in a bacterial pathogenesis. person - Examples are pain and malaise 2. Pathogenicity - pertains to the ability of a pathogenic agent to 3. Syndrome produce a disease in a susceptible individual. - is a group of signs and symptoms that are associated with a disease. - Example is AIDS VIRULENCE Phases of Infectious Diseases Ability of the microorganisms to cause diseases. 1. Incubation period degree of pathogenicity - the time between the exposure to a pathogenic organism and the onset of symptoms. FACTORS INFLUENCING MICROBIAL VIRULENCE 2. Prodromal period 1. Toxic factors - is the appearance of the signs and symptoms. 2. Enzymatic factors 3. Cellular structure 3. Clinical or illness period Host Resistance Factors - the peak of characteristic signs and symptoms of an 1. Physical barriers infection or a disease. Padayon, future RMT 🔬2  CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm 2. Cleansing mechanisms Neisseria miningitidis 3. Antimicrobial substance 4. Indigenous/Normal microbial flora or microbiota E. Colon – E. coli, bacteroides, and lactobacilli 2 types of microbiota: F. Urethra – diphtheroids, Staph.epidermidis and alpha A. Resident microbiota – temporarily inhabit, – and non-haemolytic Streptococci. multiply in, and colonize an area for months Terminology or years 1. Active immunization - is the protection of susceptible humans and domestic B. Transient microbiota – inhabit ( but do not animals from communicable diseases through the multiply) and colonize an area until they are administration of vaccines. eliminated by either the host’s inherent immune defense or competition with the 2. Acquired active immunity resident microbiota. - the specific response of the host to an invading organism. 5. Phagocytosis 3. Anamnestic immunity - process by which certain cells called phagocytes - ability of the B-lymphocytes to recall pathogens during engulf and dispose of microorganisms and cell the primary encounter leading to a higher antibody debris. response on the second encounter - Phagocytes (PMN leukocytes and macrophages) ingest and destroy bacteria and other foreign 4. Antigenic shift particles through a process known as endocytosis. - is a major genetically determined change in the 6. Inflammation antigenic property of an organism in which it - a condition that serves as a reinforcement becomes unrecognizable by the host’s immune mechanism against microbial survival and system. proliferation in tissues and organs. - Some signs that may indicate an inflammation are 5. Antigenic drift swelling, redness, burning sensation, and pain in - a minor antigenic change as a result of mutation in the affected areas the organism strains. - Components of inflammation are phagocytes, complement system, coagulation system, and 6. Complement-fixing antibodies cytokines. - these are antibodies that are attached to the 7. Immune response surface of pathogens and which kill the bacteria by - provides the human host with the ability to create a lysis. specific protective response against microorganisms. 7. Natural (innate) immunity - “memorizes” all of the encountered - non-specific response that activates chemotaxis, microorganisms or the process in which phagocytes are directed to - normal immune system removes the bacteria from the site of replication and engulf the invading the blood within 30 to 45 minutes organism. - host’s immune response may be reduced or altered due to immunocompressive drugs, 8. Neutralizing antibodies that are attached to the surface of chemotherapy, or radiation microorganism and which block surface receptors. Host Resistance Factors 9. Passive immunization Two (2) types of specific immunity: - transient type immunization that is administered to A. Humoral (antibody-mediated) immunity individuals without fully activating the person’s - based on the action of soluble proteins called immune system to create the corresponding antibodies that occur in the body fluids and on the antibodies to diseases. plasma membrane of B-lymphocytes. 10. Opsonizing antibodies B. Cellular (cell-mediated) immunity - these are attached to the surface of - based on the action of specific kinds of microorganisms and which render pathogens T-lymphocytes that directly attack the cells that are susceptible phagocytosis. infected with viruses, parasites, cancer cells, or Infectious Agent Factors transplanted cells. 1. Adherence The Different body sites and their Respective 2. Proliferation Microbiota 3. Tissue damage A. Skin – staphylococcus, propionobacteria and 4. Production of toxins corynebacterium (diphtheroids) Two (2) types of toxins: B. Mouth and oral cavity – Streptococci viridans A. Exotoxin - known to be one of the most lethal C. Upper respiratory tract – Streptococci viridans, substances. Mostly present in Gram diphtheroids and Staph.epidermidis positive and Gram negative bacteria do not require bacterial death to be D. Nasopharynx – Staph.aureus, Staph.epi, and released into circulation. Padayon, future RMT 🔬3  CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm do not produce fever to the host Epidemiology they are either secreted or excreted by study of occurrence, distribution, and cause of living microorganisms. disease or injury some examples are the cytotoxins , FACTORS CONTRIBUTING TO EPIDEMIOLOGY: neurotoxins, and enterotoxins. some bacteria that produces this kind of 1. Carrier toxins are Clostridium botulinum, ➔ person or animal that harbors and spreads a C.diphtheria, Staph.aureus and microbes that causes a disease but does not Strept.pyogenes. become ill himself. Four (4) types of carrier B. Endotoxins A. Casual/acute/transient composed of the LPS of the cell wall harbors the microorganisms present only in Gram negative bacteria temporarily for a few days or weeks stimulates the fever center in the B. Chronic carrier hypothalamus remains infected for a relatively long released when bacteria dies and cell wall time sometimes throughout its undergo lysis entire life toxicity is due to the lipid A portion of the LPS C. Convalescent carrier 5. Invasion – process of penetrating and growing in an individual who has recovered tissues. from infection but continues to harbour large numbers of the 6. Dissemination – it is the spread of microorganisms to pathogen. distant body sites. D. Active carrier Routes of Transmission an individual who has an overt 1. Airborne transmission clinical case of the disease - Respiratory spread of infectious diseases is 2. Likelihood of becoming endemic common ➔ the organism or disease are indigenous to or - Secretions are aerolized by coughing, sneezing, constantly present in a geographic area or and talking population - Tuberculosis, brucellosis, tularemia and plague 3. Likelihood of becoming EPIDEMIC maybe acquired through inhalation ➔ affects a significantly large number of people 2. Transmission by food and water in a short period of time. - infection occur via fecal- oral route 4. likelihood of becoming PANDEMIC - Gastric enzymes and juices in the stomach ➔ affects huge population across the regions prevent the survival of most organisms. like several countries or a continent - Salmonella, Campylobacter, E. coli O157:H7 5. Incidence rate 3. Close contact - refers to the passage of organism through ➔ number of times a new event occurs in a salivary, skin, and genital contact. given period 4. Cuts and bites 6. Incubation period - cause infection through the normal oral microbiota ➔ time between the exposure to a pathogen 5. Arthropods and the onset of symptoms - infection multiply within the arthropod which 7. Morbidity rate transmits the microorganisms while feeding off a ➔ number of cases of a disease in a specified human host population during a defined time interval. 6. Zoonoses 8. Mortality rate - these animal diseases that depends on the contact ➔ number of deaths due to a disease in a with animals or animal by-product for transmission population 9. Reservoir ➔ source of an infection, which may be a person, animal or any object from the environment. Padayon, future RMT 🔬4  CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm THE CONTROL OF MICROBIAL GROWTH ❖ Boiling or flowing steam - kills vegetative bacterial and fungal STERILIZATION and DISINFECTION pathogens and almost all viruses within 10 minutes, less effective on endospores. Preferred use: Mechanism of Action: Terminologies Dishes Protein denaturation 1. Sterilization basins Destruction and removal of all forms of microbial pitchers life, including endospores various equipments Usually done by steam under pressure or a ❖ Autoclaving sterilizing gas such as ethylene oxide. - very effective method of sterilization, at 2. Commercial sterilization about 15 psi (1210C), all vegetative cells and Sufficient heat treatment to kill endospores of their endospores are killed in about 15 mins. Clostridium botulinum in canned foods. Used in: Mechanism of Action: More resistant endospores of thermophilic Microbiological media, Protein denaturation bacteria may survive, but they will not germinate solutions and grow under normal storage condition. linens 3. Disinfection utensils Destruction of vegetative pathogens. dressings May make use of physical or chemical methods equipment other items that can 4. Antisepsis withstand temperature Destruction of vegetative state pathogens on and pressure. living tissues. 2. PASTEURIZATION Treatment is always by chemical antimicrobials the use of mild heating which is sufficient to kill the 5. Degerming microorganisms that can cause spoilage problem Removal of microbes from a limited area such without really damaging the taste of the product. as the skin around the injection site. Heat treatment for milk (720C for about 15 secs) kills Mostly a mechanical removal by an all pathogens and most non-pathogens alcohol-soaked swab. Used in: Mechanism of Action: 6. Sanitation Milk, cream Protein denaturation Treatment intended to lower microbial counts on certain alcoholic eating and drinking utensils to safe public health beverages (beer and levels. wine) Maybe done with a high temperature washing or by dipping into a chemical disinfectant. 3. DRY HEAT kills by oxidation effect ❖ Direct flaming Rate of microbial growth - Very effective method of sterilization Bacterial population die at a constant rate when heated or Used in: Mechanism of Action: treated with antimicrobial agents. Inoculating loops Burning contaminants to Ex. A population of 1 million microbes has been treated ashes for 1 minute, 90% dies, 100,000 microbes left. If the ❖ Incineration population is treated for another minute, another 90% will - very effective method of sterilization die and left with 10,000 survivors. Used in: Mechanism of Action: For each minute the treatment is applied, 90% of the remaining population is killed. Paper cups Burning to ashes contaminated dressings animal carcasses bags and wipes. Factors affecting the effectiveness of ❖ Hot-air sterilization antimicrobial treatments: - very effective method of sterilization The number of microbes but requires temp.at 1700C for Environmental influences about 2 hours. Time of exposure Used in: Mechanism of Action: Microbial characteristics Empty glasswares Oxidation instruments needles and glass PHYSICAL METHODS USED TO CONTROL syringes. MICROBIAL GROWTH 4. FILTRATION HEAT the passage of a liquid or gas through a screen like 1. MOIST HEAT materials with pores small enough to retain microbes. kills microorganism primarily by coagulation of Used to sterilize heat sensitive materials such as proteins (denaturation), which caused by breakage of enzymes, vaccines and antibiotic solutions. the hydrogen bonds that hold the protein. Removes microbes by passage of a liquid or gas. Most filters in use consist of cellulose or nitrocellulose Padayon, future RMT 🔬5  CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm Used in: Mechanism of Action: CHEMICAL METHODS OF MICROBIAL Sterilizing liquids Separation of bacteria CONTROL (enzymes, vaccines) that from suspending liquid Chemical agents are used to control growth of are destroyed by heat microbes on both living tissue and inanimate objects. COLD Most chemical agents merely reduce the microbial 1. REFRIGERATION population to safe levels or remove vegetative forms Has a bacteriostatic effect from objects. Used in: Mechanism of Action: A common problems to disinfection is the selection of Food, Decreased chemical an agent.No single disinfection is appropriate for all drug and culture reactions and possible circumstances. preservation changes in protein. 2. DEEP-FREEZING an effective method for preserving microbial cultures, PRINCIPLES OF EFFECTIVE in which cultures are quick-frozen between -500C and DISINFECTION 950C 1. Read the label. The label usually indicates what group Used in: Mechanism of Action: of microbes is it effective against. Food, Decreased chemical 2. Nature of material being disinfected. The organic drug and culture reactions and possible material present might interfere with the action of the preservation changes in protein. disinfectant.The pH of the medium often has a great 3. LYOPHILIZATION effect on disinfectant’s activity. Most effective method for long term preservation of 3. Disinfectant effect. Consider whether the disinfectant microbial culture will easily make contact with microbes. Water removed by high vacuum at low temp. Used in: Mechanism of Action: Food, Decreased chemical Disinfectants vs. Antiseptics drug and culture reactions and possible ➔ Disinfectants are chemical substances that applied preservation changes in protein. to non-living objects or surfaces to inhibit the growth of microorganisms. HIGH PRESSURE ➔ They prevent the spreading of germs and bacteria to ➔ Preservation of colors, nutrient values people by sterilizing the surfaces where they are Used in: Mechanism of Action: applied. fruit juices Alteration of molecular ➔ They are largely used in homes for cleaning structure of proteins and bathrooms, kitchens and floor. carbohydrates. ➔ Some disinfectants such as hydrogen peroxide are DESICCATION used in healthcares and hospitals to clean surgery ➔ Involves removing of water from microbes; primarily tools and rooms. bacteriostatic ➔ Common disinfectants are alcohols, oxidizing agents and bleaches. Used in: Mechanism of Action: ➔ Disinfectants may not necessarily eliminate all the Food preservation Disruption of microorganisms. metabolism ➔ Antiseptics are chemical agents used to destroy or OSMOTIC PRESSURE prevent the growth of microorganisms that could ➔ Results in loss of water from microbial cells cause infections and diseases. Used in: Mechanism of Action: ➔ They are applied on broken skins to kill Food preservation Plasmolysis disease-causing microorganisms that might have infected the area or keep them away from these RADIATION areas. ➔ kills microorganism in two ways ➔ Are applied on living tissues with zero injurious effect A. Ionizing (gamma rays or high energy electron) on the body surface where it is applied. - Not widespread in routine sterilization ➔ Antiseptics may also act as sanitizer for cleaning Used in: Mechanism of Action: hands to remove bacteria when a person cannot wash Sterilizing Destruction of DNA hands. pharmaceuticals and medical and dental Major differences between disinfectants and supplies antiseptics B. Non-ionizing – radiation not very penetrating Disinfectants Antiseptics Used in: Mechanism of Action: Applied on non-living items Applied on living tissues Inhibit the growth of Kill and destroy microorganisms on Control of closed microorganisms on the living environment with UV surfaces tissue lamp Disinfect areas that can spread Reduce the risk of infections by germs germs. Very toxic and injurious when used Have no injurious effect on living on living tissue. tissue Padayon, future RMT 🔬6  CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm CHEMICAL METHODS Actions of microbial control agents 1. PHENOL (Carbolic acid) 1. Alteration of membrane permeability Used in: Mechanism of Action: The plasma membrane located outside the cell wall is Original surgical Denatures proteins the target of many microbial agents. antiseptic. disrupt cell membrane The membrane actively regulates the passage of 2. ALCOHOL nutrients into the cell and the elimination of wastes from the cell. Used in: Mechanism of Action: Damage to the lipids and proteins of the plasma Disinfectants Denatures proteins membrane by antimicrobial agents causes cellular antiseptics disrupt cell membrane contents to leak into the surrounding medium and solvent in tincture interferes with the growth of the cell. 3. HALOGEN (iodine, chlorine, bromine) 2. Damage to protein and nucleic acids Used in: Mechanism of Action: Bacteria sometimes thought of as a little bags of Disinfectants Denatures proteins enzymes which are primarily proteins and are vital to antiseptics disrupt cell membrane all cellular activities. water purification The hydrogen bonds of proteins is susceptible to heat, 4. OXIDIZING AGENTS (peroxides,ozone) breakage results to denaturation of the protein. Used in: Mechanism of Action: The nucleic acids DNA and RNA are the carriers of Disinfectants Denature protein by the cell’s genetic information, damage to these nucleic antiseptics for deep oxidation acids by heat, radiation or chemicals is frequently wound lethal to the cell, the cell can no longer replicate nor water purification and carry its normal metabolic functions sterilization of food processing and medical equipments. 5. SURFACTANTS Used in: Mechanism of Action: Soaps, Decrease surface degerming reagents, tension of water antiseptics disrupt cell membranes 6. HEAVY METALS (arsenic, mercury, silver copper) Used in: Mechanism of Action: Fungistat in paints Denature protein silver nitrate cream surgical dressing burn cream catheter. 7. ALDEHYDES (Formaldehyde,glutaraldehyde) Used in: Mechanism of Action: Disinfectant and Denature protein embalming fluid 8. GASEOUS AGENTS (ethylene oxide) Used in: Mechanism of Action: Sterilization of heat Denature protein water sensitive objects 9. ANTIMICROBIALS Used in: Mechanism of Action: Disinfectants and Act against cell wall, treatment of infectious cell membranes, diseases protein synthesis DNA replication. Padayon, future RMT 🔬7  CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm Antimicrobial Agents Classification ANTIMICROBIALS 1. Bacteriostatic agents ➔ Chemical substances produced by microorganisms with the capacity to inhibit (bacteriostatic) or kill ➔ inhibit the bacterial growth but generally they (bactericidal) other microorganisms. do not kill the microorganisms. Ex. Chloramphenicol Source of Antibiotics Erythromycin Clindamycin Source ( Microorganisms) Antibiotics Produced 2. Bactericidal agents Streptomyces nodosus Amphotericin B ➔ usually kill or destroy organisms and are used Streptomyces noursei Nystatin for the treatment of life-threatening infections. Streptomyces venezuelae Chloramphenicol ➔ Example: Bacillus subtilis Bacitracin ◆ Aminoglycosides Bacillus polymyxa Polymyxin Gentamicin Cephalosporium Cephalosporins Amikacin Micromonospora purpurea Gentamicin Streptomycin Penicillium notatum Penicillin ◆ Β-lactams Ceftriaxone Streptomyces erythraeus Erythromycin Imepenem Streptomyces fradiae Neomycin Penicillin Cefotaxime ◆ Glycopeptides -\ Spectrum Activity Isoniazid Narrow-spectrum Quinolones ➔ effective against a limited number of pathogens. Bacitracin Metronidazole EXAMPLE: Antimicrobial Agents Classification Bacitracin gentamicin 1. Must be in an active form. clindamycin penicillin 2. Must able to achieve concentration at the site of erythromycin Vancomycin infection that is higher than the pathogen’s MIC to be effective. Narrow-spectrum 3. Must have “selective toxicity”. ➔ destroy different kinds of organisms. EXAMPLE: Terminology Ampicillin Rifampicin 1. Integrons - are genetic elements that are capable of Cephalosporins Trimethoprim integrating genes(cassettes) by an integrin encoded chloramphenicol Tetracycline site-specific recombinase. Ciprofloxacin 2. Minimal-inhibitory concentration (MIC) - is the Classification of Antibacterial Drugs lowest concentration of a drug that can still inhibit 1. Natural drugs bacterial growth. ➔ produced by bacteria or fungi. 3. Minimal lethal concentration - is the lowest concentration of a drug that can kill bacteria. EXAMPLE: 4. Penicillin-binding proteins - are enzymes Erythromycin, Tetracycline, (transpeptidase or transglycolase) that mediate amphotericin B Penicillin peptidoglycan cross-linking with reduced affinity for vancomycin B-lactam antibiotics. Therapeutic index - is the ratio of the toxic dose to the 2. Semi-synthetic drugs therapeutic dose and as such, the higher the therapeutic index, ➔ modified drugs with added chemical groups the more effective the chemotherapeutic agent. Transposons – DNA elements that encode transposition and EXAMPLE: excision functions and which are also able to carry antibiotic Ampicillin resistance genes among plasmids and chromosomes Carbenicillin Methicillin 3. Synthetic drugs Kinds of Antimicrobial agents ➔ chemically –produced drugs. 1. Cell wall inhibitors ➔ most selective antibiotics with a high therapeutic EXAMPLE: index. Inhibits the transpeptidase enzymes in Sulfonamides Ciprofloxacin which cell growth stops and the death of the Trimethoprim Isoniazid cells occurs. Example a. Bacitracin - inhibits the synthesis of peptidoglycan precursors Padayon, future RMT 🔬8  CLINICAL BACTERIOLOGY 1 T. Embudo BSMT - 3C Professor: Mary Grace Bayot 1st Semester Midterm ANTIBIOTIC RESISTANCE b. Β-lactams - inhibits transpeptidation ➔ Result of both the use and overuse of antimicrobial agents c. Isoniazid - acts on growing cells & can either ➔ May arise within antibiotic-producing microorganism be a bactericidal or bacteriostatic agent (autotoxicity) d. Vancomycin - inhibits the translocation and 2 TYPES OF ANTIBIOTIC RESISTANCE elongation of peptidoglycan. 1. Intrinsic Resistance ➔ Result of the biochemical make up of wild type of e. Carbenicillin organism. f. Penicillin ➔ Depends on the hydrophobic or hydrophilic nature of the 2. Protein synthesis inhibitors antibiotic and on the impermeability of the cell wall to the ➔ that binds with a 30S subunit that result in the antibiotic misreading of mRNA and 50S subunit that ➔ Passed vertically into new cell. results in the inhibition of peptidyl transferase ➔ All Gram-negative bacteria mediate this type of and peptide chain elongation. resistance through the inactivation of penicillin Example Example a. (30S) = Tetracycline, aminoglycosides b. (50S) = Erythromycin,chloramphenicol & a. Glycopeptide clindamycin - Gram-positive bacteria c. Linezolid - blocks the initial step in protein synthesis. b. Porins and LPS - Gram-negative 3. Nucleic acid inhibitors Example c. Β-lactamases - enzymes that chemically inactivate a. Rifampicin - inhibits RNA polymerase β-lactam drugs by disrupting β-lactam ring component of the b. Quinolones - interferes with DNA gyrase molecule. and topoisomerase IV and highly effective for enteric bacteria. Most clinically important β-lactamases: c. Metronidazole - disrupts DNA and is A. Class A enzymes – found in plasmids effective against anaerobic bacteria. 4. Cell membrane inhibitors B.Class C enzymes – chromosomally Example located and inducible by exposure to β-lactams. a. Polymyxin B and E 2. Β-lactamase Inhibitors - Gram- negative bacteria ➔ structurally similar with the β-lactam antibiotics and (P.aeuruginosa) also used as a functions as a substrate, thus reducing their harmful topical antibiotic. effects on the β-lactam antibiotics. 5. Cell membrane inhibitors Example Example a. Sulfamethoxazole (SMZ) a. Clavulanic acid c. Tazobactam - inhibits folic acid and metabolism b. Sulbactam and has a higher therapeutic index. ➔ Extended Spectrum β-lactamases (ESBL) b. Dapsone ➔ Can inactivate extended spectrum cephalosporins, - interferes with folic acid synthesis penicillins and aztreonam. ➔ Enzymes that are differentiated with regards to the c. Trimethoprim properties of the parent enzymes - blocks the tetrahydrofolate ➔ Carbapenems are actively against ESBL- producing synthesis strains. ➔ Indicators drugs for ESBL – ATM, CRO, & CTX ➔ Clavulanic acid is the inhibitor. ACQUIRED RESISTANCE ➔ Present only on a certain isolates that are different from the parental strains. ➔ Usually expressed as a modification of target sites or enzymatic modification of antibiotics. Example Chromosomal mutations (transformation and recombination) Padayon, future RMT 🔬9