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65 Cards in this Set
- Front
- Back
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What are antimicrobial agents? |
Compounds used to treat bacterial infections in animals and humans |
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What are antibiotics? |
Substances of microbial origin acting on microorganisms |
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What is the mode of action of an antibiotic based on? |
selective toxicity |
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What are bacteriostatic agents? |
Delay growth of a bacterium, usually form unstable bonds with target, slow, depend on host immune system to kill |
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What are bactericidal agents? |
kill, bind to bacterial target irreversibly or with high affinity |
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What is the problem with aminoglycosides? |
bactericidal but poorly active against bacteria growing in anaerobic conditions |
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What are the 2 new classes of antibiotic drugs discovered in the last 30 years? |
Linezolid and damptomycin |
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What is the structure of lactam antibiotics? |
4 membered ring structure |
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What are the 4 main types of lactam antibiotics? |
Penicillins, cephalosporins, carbapenums and monobactams |
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What is the main toxicity problem of lactam antibiotics? |
Formation of lactam/serum protein conjugate resulting in allergic reaction |
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What do lactam antibiotics inhibit? |
the last step of bacterial peptidoglycan wall synthesis, the reaction that cross-links the NAM-NAG polymer chains |
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What penicillin binding proteins? |
cytoplasmic membrane proteins with a role in rtanspeptidation and turnover, inhibited by lactam antibiotics |
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Are lactam antibiotics bacteriostatic or bactericidal? |
bactericidal |
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How do lactam antibiotics differ? |
some more effective against gram positives, some more effective against gram negatives |
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What do glycopeptides inhibit? |
peptidoglycan synthesis (transglycosilation and transpeptidation) |
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What are 2 examples of glycopeptides? |
vancomycin and teichoplanin |
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What are glycopeptides usually used to treat? |
gram-positive infections, Staphylococcus aureus |
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What do aminoglycosides target? |
bacterial ribosome (kanamycin and gentamicin) |
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What do aminoglycosides bind to? |
30S ribosomal subunit |
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What do aminoglycosides inhibit? |
protein synthesis |
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Are aminoglycosides bacteriostatic or bactericidal? |
bactericidal |
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What limits the use of aminoglycosides? |
side effects: hearing loss and impaired renal function |
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What structure are tetracyclines? |
4 fused 6 membered rings |
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What do tetracyclines target? |
bacterial ribosome |
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What do tetracyclines bind to? |
30S subunit, distorting A site, preventing alignment of aminoacylated tRNA molecule |
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What tetracyclines inhibit? |
protein synthesis |
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Are tetracyclines bacteriostatic or bactericidal? |
bacteriostatic |
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What has led to wide spread use of tetracyclines? |
low toxicity |
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What are tetracyclines used for in agriculture? |
growth promoter in animal feed |
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Why are tetracyclines no longer being used? |
bacterial resistance common |
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What is an example of a macrolide? |
erythromycin |
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What do microlides bind to? |
50S ribosomal subunit |
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What do microlides inhibit? |
protein synthesis by preventing elongation of polypeptide chain |
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Are microlides bacteriostatic or bactericidal? |
bacteriostatic for most but bactericidal for some |
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What are microlides used for in agriculture? |
used in livestock to prevent shipping sickness |
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What are lincosamides? |
differ in structure to macrolides but mode of action the same |
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What is one example of a quinolone? |
nalidixic acid |
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What do quinolones inhibit? |
DNA replication |
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Are quinolones bacteriostatic or bactericidal? |
bactericidal |
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What do quinolones inhibit? |
A-subunit of DNA gyrase |
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What do quinolones have poor activity against? |
streptococci and anaerobes that make up majority of microflora in mouth, colon and vaginal tract, unlikely to disrupt resident flora |
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How do bacteria become resistant to quinolones? |
single mutation in DNA gyrase sufficient |
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What do quinolones penetrate? |
macrophages |
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What does rifampin inhibit? |
bacterial RNA polymerase by binding to subunit |
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What is 1 example of a rifampin antibiotic? |
rifampicin |
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What disease can rifampin treat? |
TB |
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Why is their renewed interest in rifampin? |
emergence of strains of mycobacterium tuberculosis resistant to isoniazid |
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What do trimethoprim and sulfonamides inhibit? |
bacterial enzymatic pathway that produces tetrahydrofolate |
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What is tetrahydrofolate essential for? |
1 carbon metabolism |
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How do sulfonamides work? |
structurally similar to p-aminobenzoic acid, substrate for the first enzyme of pathway |
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How does trimethoprim work? |
structural analog of dihydrofolic acid, acts by competitive inhibition of enzyme dihydrofolate reductase, catalyzing the last step of pathway |
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What antibiotics inhibit protein synthesis? |
Chloramphenicol, lincosamides, macrolides |
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What antibiotics inhibit cell wall synthesis? |
B-lactam antibiotics, vancomycin |
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What antibiotics interfere with DNA gyrase? |
Quinolones and novobiocin |
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What causes emergence of resistance? |
structural changes in targets |
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What is prophylaxis? |
drugs administered to herds of animals to prevent emergence of disease |
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What is metaphylaxis? |
Medicines administered to animals housed together to treat sick animals and control spread of disease |
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How are antibiotics used for growth promotion in agriculture? |
fed as supplement in feed, sub-therapeutic levels without prescription, long time period |
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How are lactams deactivated? |
Lactamase enzymes and inhibitors |
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How are aminoglycosides deactivated? |
group addition (-phosphoryl, -adenyl, -acetyl) |
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How are tetracyclines deactivated? |
enzymatic modification |
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What are the 2 stages of antibiotic resistance? |
emergence and dissemination of resistance |
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What is emergence a result of? |
mutations in housekeeping genes structural or regulatory genes or acquisition of foreign DNA |
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What strain was a result of mass medication? |
Salmonella Typhimurium DT29 |
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What do antibiotics disturb? |
Natural flora and creates conditions that favour genetic exchange |
