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Step 1 11.1.12
Microbiology XI
| Question | Answer |
|---|---|
| What is the mech of penicillin, methicillin, ampicillin, pipericillin, cephalospirins, azetreonam, impipenem? | block cell wall synthesis by inhbiting peptidoglycan cross linking |
| What is the mech of bacitracin, vancomycin? | block peptidoglycan synthesis |
| What is the mech of sulfonamides, trimethoprim? | block nucleotide synthesis |
| What is the mech of fluoroquinolones? | block DNA topoisomerases |
| What is the mech of rifampin? | blocks mRNa synth |
| What is the mech of penicillin, methicillin, ampicillin, pipericillin, cephalospirins, azetreonam, impipenem? | block cell wall synthesis by inhbiting peptidoglycan cross linking |
| What is the mech of bacitracin, vancomycin? | block peptidoglycan synthesis |
| What is the mech of sulfonamides, trimethoprim? | block nucleotide synthesis |
| What are the 3 mechs of penicilin G and penicilin V? | 1. bind penicilin binding proteins 2. block transpeptidase crosslinking of peptidoglycan 3. activate autolytic enzymes |
| What is the clinical use of penicillin? | G+ (strep pneumoniae, S. pyogenes, actinomyces), syphilis |
| What is the mech of fluoroquinolones? | block DNA topoisomerases |
| What are the major SE of penicillin? | hypersensitivity reactions, hemolytic anemia |
| What is the mech of rifampin? | blocks mRNa synth |
| What is the mech of metronidazole? | damage DNA |
| What is the mech of chloramphenocol, macrolides, clindamycin, streptogrammins (quinupristin, dalfopristin), linezolid? | block protein synth at 50 S subunit |
| What is the mech of aminoglycosides, tetracyclines? | blcok protein synth at 30 S ribosomal subunit |
| What is the clinical use of methicillin, naficillin, dicloxicillin? | S. aureus, except MRSA which resists due to altered penicillin binding protein |
| What are the 3 mechs of penicilin G and penicilin V? | 1. bind penicilin binding proteins 2. block transpeptidase crosslinking of peptidoglycan 3. activate autolytic enzymes |
| What are the major SE or methicillin, naficillin, dicloxicillin? | hypersensitivity reactions, methicillin-interstitial nephritis |
| What is the clinical use of penicillin? | G+ (strep pneumoniae, S. pyogenes, actinomyces), syphilis |
| What are the non species clinical use of penicillin? | G+ cocci, G+ rods, G- cocci, spirochetes. not penicillinase resistant |
| What are the major SE of penicillin? | hypersensitivity reactions, hemolytic anemia |
| What allows for resistance to penicillin? | beta lactamases cleave the Beta lactam ring |
| What is the clinical coverage of ampicillin, amoxicillin? | HELPSS kill enterococci.: Haemophilus influnezae, E. coli, Listeria monocytogenes, Proteus mirabilis, salmonella, shigella |
| What is the class of methicillin, naficillin, dicloxicillin? | penicillinase resistant penicillins |
| What are the SE ampicillin, amoxicillin? | hypersensitivity, ampicillin rash, pseudomembranous colitis |
| What is the mech and resistance development to penicillinase for the methicillin, naficillin, dicloxicillin? | mech is same as penicilling: beta lactams. resist penicillinase because of bulkier R group |
| What is the clinical use of methicillin, naficillin, dicloxicillin? | S. aureus, except MRSA which resists due to altered penicillin binding protein |
| What are the major SE or methicillin, naficillin, dicloxicillin? | hypersensitivity reactions, methicillin-interstitial nephritis |
| What is the mech of ampicillin, amoxicillin? | beta lactam, but wider spectrum but penicillinase sensitive. amoxicillin has better oral availability than ampicillin |
| What should ticarcillin, carbenicillin, piperacillin be administered with to resist penicillimase? | clavulanic acid |
| What do you give with ampicillin, amoxicillin to make them resist penicillinase? | clavulanic acid |
| What is the major SE of ticarcillin, carbenicillin, piperacillin? | hypersensitivity rxn |
| What is the clinical coverage of ampicillin, amoxicillin? | HELPSS kill enterococci.: Haemophilus influnezae, E. coli, Listeria monocytogenes, Proteus mirabilis, salmonella, shigella |
| What are the Beta lactamase inhibitors? | CAST: clavulanic acid, Sulbactam, tazobactam |
| What are the SE ampicillin, amoxicillin? | hypersensitivity, ampicillin rash, pseudomembranous colitis |
| What is the mech of the cephalosporins? | beta lactam drugs which inhibit cell wall synth but less susceptible to penicillinase |
| What is the mech of ticarcillin, carbenicillin, piperacillin? | same as penicillin, anti pseudomonals |
| What organisms are not covered by cephalosporins? | LAME: listeria, Atypicals ( Chlamydia, Mycoplasma), MRSA, Enterococci |
| What is the clinical use of ticarcillin, carbenicillin, piperacillin? | Pseudomonas spp, G- rods. |
| What are the 1st gen cephalosporins and what are they effective against? | cefazolin, cephalexin. Proteus miribilis, E. coli, Klebsiella PEcK |
| What should ticarcillin, carbenicillin, piperacillin be administered with to resist penicillimase? | clavulanic acid |
| What are the 2nd gen cephalosporins and what are they effectivde against? | cefoxitin, cefaclor, cefuroxime. HEN PEcKS: Haemophilus influenzae, Enterobacter aerogenes, Neisseria spp, Proetus mirabilis, E. coli, Klebsiella, Serratia marcese |
| What is the major SE of ticarcillin, carbenicillin, piperacillin? | hypersensitivity rxn |
| What are the Beta lactamase inhibitors? | CAST: clavulanic acid, Sulbactam, tazobactam |
| What is the mech of the cephalosporins? | beta lactam drugs which inhibit cell wall synth but less susceptible to penicillinase |
| What organisms are not covered by cephalosporins? | LAME: listeria, Atypicals ( Chlamydia, Mycoplasma), MRSA, Enterococci |
| What are the 1st gen cephalosporins and what are they effective against? | cefazolin, cephalexin. Proteus miribilis, E. coli, Klebsiella PEcK |
| What are the 2nd gen cephalosporins and what are they effectivde against? | cefoxitin, cefaclor, cefuroxime. HEN PEcKS: Haemophilus influenzae, Enterobacter aerogenes, Neisseria spp, Proetus mirabilis, E. coli, Klebsiella, Serratia marcese |
| What are the 3rd generation cephalospirins and what are they effective against? | ceftriaxone, cefotaxime, ceftazidime. good against serious G- infections resistant to other lactams. Ceftriaxone: meningitis, gonorrhea. Ceftazidime: pseudomonas |
| What is the 4th generation cepholosporin and what is it effective agaisnt? | incr activity against pseudomonas ans G+ organisms |
| What are the major SE of cephalosporins? | hypersensitivity, vit K deficiency, incr nephrotoxicity of aminoglycosylides, disulfram rxn with ethanol |
| What is the mech of aztreonam? | monobactam resistant to Beta lactamases. inihibts cell wall synth (binds PBP3). syngistic with aminoglycosylides. no cross allergenicity |
| What is the clinical use of aztreonam? | G- rods only. not for G+ or anaerobes.for penicillin allergic pt and those with renal insufficiency who cant tolerate aminoglycosylides |
| What are the major SE for aztreonam? | usually non toxic. occasional GI upset. no cross sensity w penicillin or cephalosporins |
| What is the mech of imipenem/cilastatin, meropenem? | broad spectrum Beta lactamase resistant carbapenem. always given with cilastatin (inhibits renal dehydropeptidase I) |
| What is the use of imipenem/cilastatin, meropenem? | G+ cocci, G- rods, anaerobes. wide spectrum but SE limit its use to life threatening infections. meropenem is a little better |
| What are the major SE of imipenem/cilastatin? | GI distress, skin rash, CNS toxicity, seizures at high plasma levels |
| What is the mech of vancomycin? | inhibits cell wall mucopeptide formation by binding D-ala D-ala protion of cell wall precursors. bacterocicdal. |
| What is the clinical use of vancomycin? | G+ only. serious, multidrug resistant orgamisms. like S. aureus, enterococci, Clostridium difficle. |
| What are the major SE of vancomycin? | nephrotoxicity, ototoxicity, thrombophlebitis, diffuse flushing "red man" syndrome (prevent with antihistamine or slow infusion). does NOT have mant problems |
| How does resistance to vancomycin develop? | AA change from Dala Dala to Dala Dlac |
| Which abtx attack the 30 S subunit? | AT. aminoglycosides {bactericidal} |
| Which abtax attack the 50 S subunit? | Chloramphenicol, clindamycin (bacterostatic) Erythromycin (macrolides) (bacterostatic Linezolid (vaires) CEL |
| What are the aminoglycosylides? | Gentamycin, neomycin, amikacin, tobramycin, strpetomycin Mean GNATS can NOT kill anaearobes |
| What is the mech of Gentamycin, neomycin, amikacin, tobramycin, strpetomycin? | bactericidal. inhibits formation of initiation complex and cause misreading of mRNA. Require O2 for uptake. thus ineffective against anaerobes |
| What is the clinical use of Gentamycin, neomycin, amikacin, tobramycin, strpetomycin? | aminoglycosalides. for severe G- rods. syndergistic with beta lactams. neomycin used for bowel surgery |
| What are the major SE of Gentamycin, neomycin, amikacin, tobramycin, strpetomycin? When might they be increased? | aminoglycosylides. nephrotoxicity(esp w cephalosporins), ototoxicity (esp w loop diruretics), teratogen |
| How does resistance to Gentamycin, neomycin, amikacin, tobramycin, strpetomycin develop? | transferase enzymes inactivate drug by acetylation, phosphrylation or adenylation |
| What is demeclocycline? | ADH antagonist, acts as diuretic in SIADH |
| What is the mech of tetracycline, doxycycline, demeocycline, minocycline? | bacteriostatic. bind to 30S and prevent attatchment of aminoacyl t-RNA. limited CNS penetration. |
| How is doxycline eliminated and who should not get it? | fecally eliminated, dont use in renal failure |
| What should tetracycline, doxycycline, demeocycline, minocycline not be taken with? | milk, antacids, iron containing preps because they will inhbits its abdorbtion |
| What is the clinical use of tetracycline, doxycycline, demeocycline, minocycline? | Borellia burgdoferi, M. pneumoniae. drugs ability to accumlulate in the cell makes it effective against Rickettsia, Chlamydia |
| What is the SE of tetracycline, doxycycline, demeocycline, minocycline? | GI distress, discoloration of teeth, inhbition of bone growth in kids, photosenstitivty. CONTRA in pregnency |
| How does resistance to tetracycline, doxycycline, demeocycline, minocycline develop? | decr uptake into cells or incr efflux by plasmid qtransport pumps |
| What is the class of erytromycin, azithromycin, clarithromycin? | macrolides |
| What is the mech of erytromycin, azithromycin, clarithromycin? | bacteriostatic. bind 23S rRNA of 50S subunit to block translocation |
| What is the clinical use of erytromycin, azithromycin, clarithromycin? | atypical pneumonias (mycoplasma, chlamydia, legionella), URI, STDs, G+ cocci (streptococcus if pt allergic to penicillin), Neisseria |
| What are the SE of erytromycin, azithromycin, clarithromycin? | prolonged QT interval (esp erythromycin), GI discomfort, acute cholestatic hepatitis, eosinophilia, skin rashes. |
| What are some important drug interactions of erytromycin, azithromycin, clarithromycin? | incr serum theophyllines, oral anticoagulants |
| How does resistance to erytromycin, azithromycin, clarithromycin develop? | methylation of 23 S rRNA binding site |
| What is the mech of chloramphenicol? | blocks peptide bond formation at 50 S rbiosomal unit. bacterostatic. |
| What is the clinical use of chloramphenicol? | meningitis (H. influnza, Nesseria meningitidis, Step. pneumoniae). conservative use owing to toxicity but still used in developing countries due to low cost |
| What is the toxicity of chloramphenicl? | anemia, aplastic anemia, gray baby syndrome (b/c infants lack UDP glucuronyl transferase) |
| How does resistance to chloramphenicol develop? | plasmid encoded acetyltransferase that inactivates drug |
| What is the mech of clindamycin? | blocks peptide bond formation at 50S ribosomal subunit,. bacteriostatic |
| What is the clinical use of clindamycin? | anaerobic infections (Bacteroides fragilis, Clostridium perfingens) in aspiration pneumonia and lung absesses |
| How do you treat anaerobic bacteria above the diaphragm as opposed to below? | clindamycin above, metranidazole below |
| What are the major SE of clindamycin? | pseudomembranous colitis (C. difficle overgrowth), fever, diarrhea |
| What is the mech of sulfamethoxazole (SMX), sulfisoxazole, sulfadiazine? | PABA antimetabolites inhibit dihydropteroate synthetase. bacteriostatic |
| What is the clinical use of sulfamethoxazole (SMX), sulfisoxazole, sulfadiazine? | G+, G-, Norcardia, Chlamydia. Triple sulfas or SMX for simple UTI |
| What are the major SE of sulfamethoxazole (SMX), sulfisoxazole, sulfadiazine?? | hypersensitivity reactions, hemolyisis if G6PD deficient, nephrotixicity (tubulointerstitial nephritis), photosensitivity, kernicterus in infants, displace warfarin from albumin |
| How does resistance to sulfamethoxazole (SMX), sulfisoxazole, sulfadiazine develop? | altered enzme (bacterial dihydropteroate sythetase), decr uptake, or incr PABa synth |
| What is the mech of trimethoprim? | inhibits bacteria DHF reductase. bacteriostatic |
| WHat is the clinical use of trimethoprim? | used in combo tieh sulfonimdes, causing sequential block of folate synthesis. combo used for UTI, Shigella, Salmonella, Pneumocystis jiroveci pneumonia |
| What are the major SE of trimethoprim? | megaloblastic anemia, leukopenia, granulocytopenia (may alleviate with folinic acid supplement) |
| What do all flouroquinolones end with? | floxacin except enoxacin, and nalidixic acid which is just a quinolone |
| What is the mech of the fluoroquinolones? | inhibit DNA gyrase (topoisomeraseII), bacterocidal. not taken with antacids |
| What is the clinical use of fluoroquinolones? | G- rods of urinary and GI tract (including pseudomonas), Neisseria, some G+ organisms |
| What are the major SE of fluoroquinolones? | GI upset, superinfections, skin rash, HA, dizziness. Contraindicated in children and pregnant women b/c of cartilage damage. |
| What might fluoroquinolones cause in adults vs kids? | tendonitis and tendon rupture in adults, leg cramps and myalgias in kids |
| How does resistance to fluoroquinolones happen? | chromosome encoded mutation in DNa gyrase |
| What is the mech of metronidazole? | forms free radical toxic metabolites in bacterial cell that damage DNA. bacteriocidal and antiprotozoal |
| What is the clinical use of metronidazole? | GET GAP on the Metro: Giardia, Entamoeba, Trichomonas, Gardnerella vaginalis, Anaerobes (bacteroides, C. difficle) |
| How is metronidazole used in peptic ulcer disease? | used with bismuth and amoxicillin or tetracyclin for triple therapy against H. pylori |
| What is the major SE of metronidazole? | disulfram reaction with alcohol, HA, metallic taste |
| What is the prophylactic Tx for M. tuberculosis? | isoniazid |
| What is the tx for M. tb? | Rifampin, isoniazide, Pyrazinamide, ethambutol |
| What is the prophylactic Tx for Mycobacterium avium-intracellulare? | azithromycin |
| What is the tx for mycobacterium avium-intracellulare? | azithromycin, rifampin, ethambutol, streptomycin |
| What is the tx for mycobacteriu leprae? | dapsone, rifampin, clofazimine |
| What is the mechanism of isonizide? What is required for its activation | decr synth of mycolic acids. bacteria catalase peroxidase needed to convert INH to active metabolite |
| What is the clinical use of isoniazide? | M. tb. only solo prophylaxis for tb |
| What is the major SE of isoniazide? How can some of them be avoided? | neurotoxicity, heptotoxicity, lupus. pyridoxone (B6) can prevent neurotoxicity, lupus |
| What is the mech of rifampin? | inhibits DNA dependent RNA pol |
| What is the clinical use of rifampin? | M. tb. delays resistance to dapsone if used with leprosy. used for meningococal prophylaxis and chemoprophylaxis in contancts of children w H influenza type B |
| What are the major SE of rifampin? | minor hepatoxicity and drug interactions (incr P-450), orange body fluids (nonhazrdous side effects) |
| What are the 4 R's of rifampin? | RNA polymerase inhibitor, Revs up microsomal P-450, Red/organge body fluids, Rapid resistance if used alone |
| What is the mech of pyrazinamide? | inhibits mycolic acid production by blocking FA synthase I. effective in acid pH of phagolysosomes where TB engulfed by macrophages is found |
| What is the clinical use of pyrazinamide? | M. tb |
| What are the SE of pyrazinimide? | hyperuricemia, hepatotoxicty |
| What is the mech of ethambutol? | decr carbohydrate polymerization of mycobacterial cell wall by blocking arabinosyltranferase |
| What is the clinical use of ethambutol? | mycobacterium tuberculosis |
| What are the major SE of ethambutol? | optic neuropathy (RG color blindness) |
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