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MICR- ANTIMICROBIAL COMPOUNDS AND RESISTANCE MECHANISMS 2025 2026. A+ GRADED, Exams of Veterinary

MICR- ANTIMICROBIAL COMPOUNDS AND RESISTANCE MECHANISMS 2025 2026. QUESTIONS WITH CORRECT AND VERIFIED ANSWERS. A+GRADED. Bacteriostatic Inhibits bacteria growth, relies on host defence to clear bacteria. Narrow spectrum antibiotics Active against small group of bacteria Broad spectrum antibiotics active against much wider variety of bacteria Resistance When organism no longer responds to therapy, treatment won't stop infection Sensitive organism responds to antimicrobial

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2024/2025

Available from 07/12/2025

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A+GRADED. Bacteriostatic Inhibits bacteria growth, relies on host defence to clear bacteria. Narrow spectrum antibiotics Active against small group of bacteria Broad spectrum antibiotics active against much wider variety of bacteria Resistance When organism no longer responds to therapy, treatment won't stop infection Sensitive organism responds to antimicrobial What are the 3 antimicrobial targets? - Cell wall synthesis - Nucleic Acid synthesis - Protein synthesis Antimicrobial effect in cell wall synthesis? - most commonly used - can't build/destroys cell wall Types of cell wall synthesis antimicrobials? - Beta Lactams *penicillins *cephalosporins *carbapenems *monobactams - Vancomycin - Bacitracin Antimicrobial effect in nucleic acid synthesis? prevents production of proteins -30S subunit *tetracyclines *aminoglycosides What are 5 the beta-lactam antibiotics? What do they target? - cell wall synthesis inhibition - beta-lactam ring is central component of beta-lactam antibiotics -penicillins, amoxicillin, cephalosporins, minocyclines, carbapenems What do beta-lactams specifically act on? transpeptidase enzyme - it crosslinks NAM and NAG in the peptidoglycan layer - inhibiting this enzyme= no peptidoglycan layer What are the 5 types of penicillins? - Penicillin G - Penicillin V - Cloxacillin - Amoxicillin - Piperacillin What are the 4 important types of cephalosporins and their generations? 1st gen- ampicillin 2nd gen- cefazolin 3rd gen- ceftazidime, ceftriaxone, cefixime Any antibiotic beginning with "chef" is what type of antibiotic? Cephalosporins Which are the broadest vs narrowest beta-lactams? Last line defence? - Penicillin is narrowest - Cephalosporins | st gen is broader than penicillins and gets broader throughout generations - Carbapenems are last line defence, very broad What types of bacteria do beta-lactams work on? gram pos and neg what type of spectrum are penicillin and ampicillin. What are the 3 main families of protein synthesis inhibitors? - Tetracyclines - Macrolides - Chloramphenicol What subunit do tetracyclines bind to? 30S (prevents attachment of tRNA to ribosome) What subunit do macrocodes and chloramphenicol bind to? 50S (prevents bond from being formed) Name on important type of macrolide? azithromycin What are nucleic acid inhibitors called? Fluoroquinolones What is good about fluoroquinolones? - good drugs - broad spectrum of activities - used for UTIs - oral pill - penetrates tissues well What to metabolic inhibitors inhibit? folate What 2 types of metabolic inhibitors are there? - trimethoprim - sulfamethoxazole Trimethoprim vs sulfamethoxazole? - T= competitive inhibitor of dihydrofolate reductase - S= competitive inhibitor of synthesis of DHF What are the 2 types of resistance? - intrinsic What does the minimum inhibitory concentration have to be to be able to use an antibiotic? LOW What is a factor that bacteria mutates? Short replication time (20 mins) What are the 4 types of bacterial resistance mechanism? 1. efflux pump 2. reduced permeability 3. enzymatic inactivation 4. altered binding site Describe efflux pump bacteria pumps the antibiotic out describe reduced permeability changes pore sizes on cell membrane, not enough antibiotic can get in to kill bacteria explain enzymatic inactivation produces an enzyme that breaks down the antibiotic Explain altered binding site change binding site for antibiotic so the antibiotic doesn't work What are the downsides of resistance mechanisms for bacteria fitness/metabolic cost (uses energy) - the wild type of the bacteria is most fit so it will revert to that if you take the antibiotic away What are the 2 types of resistant mechanisms? - Always on (usually acquired) - inducible (intrinsic) What 2 places can resistance genes be found? - bacterial chromosome intrinsic) - plasmic (circular DNA strand) Explain plasmids - circular dsDNA - exist and replicate independently - may integrate with chromosome - MOST STUFF WORRIED ABOUT IS PLASMID MEDIATED What does E. coli cause commonly? 80% of UTIs What was used to treat E coli UTIs? Ciproflaxin What are some elements of selective pressure? - over use of antibiotics - we give animals the same ones as us - not fully completing prescriptions - getting into environment from animals and getting back into us through water What are the 3 classes of gram positive resistant organisms? - Methicillin resistant staphylococcus aureus (MRSA)] - vancomycin resistant enterococcus (VRE) - Clostridium difficile (CDI) What are the 2 phenotypes of gram negative resistant organisms? - Extended spectrum beta-lactamase producers (ESBLs) - Carbapenem resistant organisms (CRE/CPE) (IN MOST GRAM NEGATIVE BACTERIA) What is one of the most challenging hugs to treat and manage? C diff What do ESBLs do? knock out Ist 2nd and 3rd gen cephalosporins. What is the other resistant bacteria? mycobacterium tuberculosis What does S. aureus colonize? What happens in hospitals for MRSA protection? Swabbing and screening, isolation if positive How to prevent MRSA HAND HYGEINE What are the 2 main species of enterococcus? Where are they found? E. faecium E. faecalis - found in GUT What are VRE resistant to? Anything that starts with a C or S What kind of resistance do VREs have a lot of? intrinsic - means very few treatment options How are VREs screened for Rectal swab be they live in gut How are VREs transmitted? Environmental contamination (clean environment to protect, proper poop disposal, etc) What resistance mechanism do VREs use? Target change - low affinity molecules to not bind vancomycin What is a nosocomial infection? hospital/healthcare associated infection What is the biggest risk factor for C. diff being on antibiotics - immunocomp also a risk - one of most common nosocomial infections How to preven C. diff hand hygiene and cleaning environment where are ESBLs usually found - gram negs, E. coli and K. pneumoniae What do ESBLs do? enzyme that breaks down penicillin and cephalosporins (beta lactams) What are ESBLs sensitive to? Carbapenems What are ESBL mechanism of resistance? enzymatic inactivation What are the 4 risk factors for ESBL infections? - antibiotic use - travel - hospitals - ESBL organisms in GI tract What are carbapenem resistant organisms (CRO)? any gram negative in GI tract that is resistant to carbapenem - risk from travel, overuse of antibiotics, etc