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Antimicrobials1. Which of the following statements regarding penicillins is FALSE?a. They inhibit cell wall synthesis by blocking transpeptidation of peptidoglycan - trueb. Penicillin G has no activity against Gram-negative organisms <= active against G+ves, G-ve cocci, and non-b-lactamase anaerobes. Not effective against G-ve baccilic. Penicillin sensitization occurs as a result of exposure to antigens produced by the degradation of penicillind. Approximately 90% of renal elimination takes place through tubular secretion – and only 10% by filtratione. Oral administration of penicillin should precede or follow food by at least 1 hour – poorly absorbed with food2. With regard to antibioticsa. Tetracyclines inhibit transpeptidation by inhibiting peptidyl transferase activity – 30S binding, bacteriostaticb. Aminoglycosides bind to the 50S ribosomal subunit and inhibit translocation – 30Sc. Sulphonamides inhibit cell wall synthesis – folic acid synthesis thus bacterial DNA synthesisd. Quinolones inhibit DNA gyrase and lead to unwinding of DNA supercoils <= e. Penicillin causes incorrect reading of MRNA at 30S subunit – block transpeptidation and cell wall synthesis3. The mechanism of action of beta-lactam antibiotic isa. To inhibit hydroxylation in bacterial cell wall synthesisb. To inhibit transpeptidation in peptidoglycan synthesis <=c. To add alanine to the peptidoglycan chaind. To promote transpeptidation in peptidoglycan synthesise. To add amino sugar to N-acetyl muramic acid4. Aminoglycosidesa. Are bacteriostatic – bacteriocidal inhibitor of protein synthesis via 30s bindingb. Bind to receptors on the 40S subunit of the bacterial ribosome – 30Sc. Are well absorbed after oral administrationd. Generally reach high levels in CSFe. Are ineffective as monotherapy against streptococci – need cell wall active drug like vancomycin for synergism5. Which of the following drugs acts as an antimicrobial agent by blocking the attachment of IRNA molecules to ribosomes?a. Gentamicin b. Penicillinc. Chloramphenicold. Tetracycline <=e. Clindamycin6. The incidence of aplastic anaemia following use of chloramphenicol is approximatelya. 1 in 100 (1%)b. 1 in 500 (0.2%)c. 1 in 1000 (0.1%)d. 1 in 10000 (0.01%)e. 1 in 30000 (0.003%) <= 1/25,000 – 1/40,000 (also causes gray baby syndrome)7. Isoniazida. Is a second line drug for the treatment of TBb. Acts by inhibition of DNA gyrase – pyridoxine-like, inhibits mycobacteral cell wallsc. Causes clinical hepatitis in 1% of recipients <= also neurotox (need pyridoxine) and inhibits metabolism of other drugsd. Is active only against M tuberculosis organisms which are extracellular – penetrates cellse. Causes an irreversible neuropathy – reversible with pyridoxine8. With regards to penicillina. Concentrations in most tissues are equal to serum <= trueb. Mostly excreted by glomerular filtration – 10% vs 90% secretionc. Half life is 2 hours – 30mins (is 30mins-1hour for most)d. Does not need to be adjusted in renal failure – does b/c secretione. Can be used for enterococcal meningitis 9. With respect to antiviral therapya. Indinovir is a reverse transcriptase inhibitor – protease inhibitor (antiHIV, Iggy Pop)b. Acyclovir is only effective against herpes simplex and varicella zoster virus – this is true for in vivo, it has only in vito activity against EBV and CMVc. Zidovudine (AZT) is a reverse transcriptase inhibitor and can only be administered orally – can be given oraaly and is an NRTId. Protease inhibitors prevent uncoating of viral nucleic acids – prevent assembly of infectious viron coree. Valacyclovir is converted to acyclovir when taken orally <= true10. Which drug causes hypoprothrombinaemia and bleeding disorders?a. Cefotetan <= also cefamandole and cefoperazone, these three can also cause disulfiram-like reaction like trimethoprim and metronidazole (inhibition of aldehyde dehydrogenase w/ accumulation of acetaldehyde -> flushing , N&V, HA)b. Cephalexinc. Cefotaximed. Cefaclore. Ceftazidime11. acyclovira. dose is 12-20mg five times daily – 200-800mg 5x/day (short t ? 2.5-3h)b. does not work on viruses with thymidine kinase – this is required for the initial viral specific phosphorylation of acyclovir, and strains without are cross resistant to acyclovir and ganciclovirc. does not work on CMV – true in vivod. is a guanasine analogue <= guanosine derivativee. ?12. metronidazolea. is shown to be teratogenic in humans – animal studies, no evidence in humansb. causes a disulfiram-like reaction <= truec. inhibits alcohol dehydrogenase – acetaldehyde =(aldehyde dehydrogenase)=> acetated. is recommended as a single dose for giardiasise. ?13. Which of the following is a cell wall inhibitor?a. Cephalosporins <=b. Tetracycline – 30s, inhibit tRNA to acceptor site or mRNA/ribosome complex, bacteriostaticc. Ciprofloxacin – fluroquinolone, DNA gyrased. ?e. ?14. tetracyclinea. may cause photosensitivity <=b. does not cause enamel discolouration – Ca2+ chelatesc. ?d. ?e. ?15. gentamicina. is water soluble but unstable in solutionb. is an antibiotic which is oxygen dependent <= correctc. ?d. ?e. ?16. which antibiotic is resistant to beta-lactamase?a. Piperacillin – and ticarcillin are anti-pseudomonas (Gram-ve bacilli)b. Cloxacillin <= anti-staph penicillins include methicillin (interstitial nephrtitis), nafcillin, oxacillin and the isoxazolyl penicillins cloxacillin, dicloxacillin, flucloxacillinc. Amoxicillin – ampicillin are extended spectrum but still b-lactamase suceptable (hence use w/ b-lactam inhibitos like clavulanic acid)d. Penicilline. ?17. Regarding trimethoprim, which is INCORRECT?a. Synergistic with sulphonamides - sequential synergismb. Folate synthesis disruption - truec. Less toxic to humans than to bacteria - trued. Is bacteriocidal <= bacteriostatice. ?18. aminoglycosidesa. resistance is plasmid mediated <= trueb. does not cross speciesc. ?d. ?e. ?19. Which is INCORRECT?a. Disinfectants clean non-living fieldsb. Antiseptics clean living fieldsc. Antiseptics in low dose can promote bacterial growth <= correctd. Alcohol kills all bacteria and spores- not sporocidale. ?20. Penicillin Ga. Hypernatraemia is not reportedb. Has good penetration to the eye – eye, prostate and normal CNS is poorc. 100000u intrathecally can cause seizures <=d. 50% of people who clain allergy will have an allergic reaction on further exposure – ‘small number’e. ?21. metronidazolea. commonly causes constipation – nausea, diarrhoea, hairy back tongue, headache, insomnia..b. inhibits alcohol dehydrogenase – aldehyde dehydrogenasec. is useful in treatment of urogenital trichomonas – antiprotozoal, treatment of choice of C. dif, also in H.pylori, anti bacteriodesd. ?e. ?22. erythromycina. is predominantly renally excreted – biliary secretion t1/2 2hrb. is a cell wall inhibitor – 50S inhibitorc. is bacteriostatic only – in high conc bacteriocidald. is effective against Campylobacter jejuni <=e. ?23. Which antiseptic is commonly used in medical practice?a. Ethyl alcohol 70% <= need 60-90% to be effectiveb. Ethanol 30%c. Formaldehyded. Isopropyl alcohol 10%e. All of the above24. penicillins reach high concentrations ina. vitreous humour – nots eye, prostate or normal CNSb. CSF with normal meninges – only when inflammedc. Proximal tubular fluid in kidneys <=d. ?e. ?25. All are cell wall inhibitors EXCEPT:a. Vancomycinb. Erythromycin <= 50Sc. Penicillind. Ceftriaxonee. Imipenem26. Regarding erythromycina. It has a large cross reactivity with penicillinb. It is bacteriostatic onlyc. It is ineffective against Gram positive organismsd. It is inactivated by beta-lactamasese. It binds to the 50S subunit on the bacterial ribosome <=27. Regarding metronidazole, all of the following are true EXCEPT:a. It is useful against trichomonasb. Is used to treat garnerellac. Causes a metallic taste in the mouthd. Inhibits alcohol dehydrogenase <= aldehyde dehydrogenasee. Is used to treat giardiasis28. Which skin antiseptic is commonly used?a. Ethyl alcohol 70% <= must be 60-90%b. Ethanol 30%c. Isopropyl alcohol 10%d. Formaldehydee. Boric acid 5%29. Acyclovir is active against all of the following EXCEPT:a. Herpes simplexb. CMV <= only in vivoc. Herpes zosterd. Varicellae. ?30. A woman aged 43 presents with a petechial rash on her legs and a platelet count of 8,000. She has recently been receiving treatment for an ear infection. Which of these agents is MOST likely to be the cause of her current problems?a. Penicillinb. Amoxycillinc. Cotrimoxazole <= as folate blocking agents can cause thrombocytopaenia, granulocytopaenia, aplastic/megaloblastic anaemiad. Erythromycine. Roxythromycin31. Which of the following does NOT act primarily by inhibiting protein synthesis?a. Gentamicinb. Vancomycin <= D-Ala-D-Ala bindingc. Erythromycind. Clindamycine. Chloramphenicol32. Which of the following is a contraindication to the use of griseofulvin?a. Diabetes mellitusb. Multiple myelomac. Porphyria <= (an antifungal)d. Alcoholic hepatic cirrhosise. Sickle cell disease33. with respect to hypersensitivity reactions to penicillins:a. if a patient has had a previous reaction to penicillin, the risk of allergic reaction is greater than 80%b. small children are at higher risk of allergic reaction to penicillinc. less than 1% of patients with a past history of having taken penicillin without reaction will have an allergic reaction <=d. the risk of sensitization is not related to the amount of penicillin received in the paste. ceftriaxone is a safe alternative for those with a past history of anaphylaxis to penicillin34. which of the following is NOT true for norfloxacin?a. It is poorly absorbed from the gastrointestinal tract <=b. It is effective in salmonella enteritisc. It inhibits DNA synthesis in susceptible microbes – fluroquinalone so blocks DNAgyrased. It can increase serum theophylline levels if administered concurrently e. It is mainly excreted by the kidney – true, secreted (and can be blocked by probenecid)35. which of the following is NOT an adverse effect of gentamycin?a. Haemolytic anaemia <=b. Prolonged neuromuscular blockadec. Eighth cranial nerve damaged. Impairment of renal functione. Vestibular damage36. A 25 year old woman being treated for pneumonia develops clinical jaundice. Her serum bilirubin level is 40 micromoles per litre (normal up to 17) with a conjugated bilirubin level of 30 micromole per litre (normal up to 7). Which antibiotic is MOST likely to have caused this effect?a. Vancomycinb. Ceftriaxonec. Penicillind. Doxycyclinee. Erythromycin <= liver tox and can cause acute cholestatic hepatitis37. cephalosporinsa. promote cross linking in bacterial cell wallsb. bind to penicillin binding proteins <=c. increase peptidoglycan synthesisd. promote the transpeptidation reactione. are inactive in the synthesizing cell wall38. macrolide antibioticsa. are usually active against Neiserria species <=b. are bacteriostatic but not bactericidal – in high doses arec. bind at the 30S ribosome subunit – 50Sd. are unaffected by plasmid mediated resistancee. enhance metabolism by cytochrome pathways - inhibit39. which of the following is a second generation cephalosporin?a. Cefaclor <=b. Ceftazidime – 3rdc. Cephalexin – 1st w/ cefazolind. Cefotaxime – 3rde. Cephalothin – 1st40. the cephalosporin with the higest activity agains gram positive bacteria isa. cefuroximeb. cefotaximec. cefaclord. cefipimee. cephalothin <= 1st41. Which of the following antibiotics does not possess a beta-lactam ring?a. Penicillinsb. Cephalosporinsc. Fluoroquinilones <= DNA gyrase inhibitord. Carbapenemse. Monobactams42. Which of the following drugs does not exert its action by inhibiting cell wall synthesis?a. Vancomycinb. Erythromycin <= 50Sc. Penicillind. Ceftriaxonee. Imipenem43. Erythromycina. Has a large cross-reactivity with the penicillinsb. Is bacteriostatic onlyc. Is ineffective against gram positive organismsd. Is inactivated by beta lactamasese. Binds to the 50S subunit of the bacterial ribosome <=44. Metronidazolea. Inhibits alcohol dehydrogenase – aldehyde dehydrogenaseb. Is effective for vaginal trichomoniasis <=c. Does not cause a metallic taste in the mouthd. Turns urine greene. ?45. penicillins reach high concentrations ina. vitreous humourb. CSF with normal meningesc. Proximal tubular fluid in kidneys <=d. ?e. ?46. zidovudine (AZT)a. has a short half life <=b. inhibits viral thymidine kinase – NRTI: are prodruges converted to active drug by the kinase, then inhibit the reverse transcriptasec. has no activity against retrovirusesd. ?e. ?47. The antiviral drug which acts on reverse transcriptase isa. Acyclovir - nob. Zidovudine <= NRTIc. Ganciclovir – similar to acyclovir (but also CMV)d. Vidarabine e. All of the above48. acyclovira. is commonly given in doses of 10-20mg tdsb. is used to treat CMVc. is a guanosine analogue <=d. acts to inhibit viral entry into cellse. is only available intravenously49. amantadinea. is an antiviral drugb. produces insomnia not sedationc. causes acute psychosisd. potentiates dopaminergic functione. all of the above <=50. doxycyclinea. acts to inhibit nucleic acid synthesis – binds 50S so protein synthesisb. may cause photosensitivity <= truec. ?d. ?e. ?51. all of the following inhibit nucleic acid synthesis EXCEPT:a. norfloxacin – blocks DNAgyraseb. trimethoprim - truec. rifampicin – anti TB, blocks RNA polymerased. sulfasalazine – sulfonamide, used for inflammorty condistion like IBSe. chloramphenicol <= 50s blocker52. gentamicina. is not nephrotoxicb. decreases the effect of neuromuscular junction blocking drugsc. may be given orallyd. enters cells by an oxygen dependent influx <=e. has a large therapeutic index53. Which of the following is not true of trimethoprima. It is useful in the treatment of UTIb. It is bactericidal - bacteriostaticc. It is an antifolate antimetabolite drugd. ?e. ?54. A patient with impetigo would be most likely to respond toa. Streptomycinb. Kanamycinc. Metronidazoled. Cephalexin – 1st gen cephalosporine. Phenoxymethylpenicillin ................
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