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USMLE S1 > Antimicrobials > Flashcards

Antimicrobials Flashcards

1
Q

in penicillin bactericidal or bacteristatic?

A

bactericidal

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2
Q

griseofulvin has what effect on P450?

A

inducer

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3
Q

methylation of a ribosomal binding site in bacteria is a common resisitance mechanism against which antibiotics?

A

aminoglycosides

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4
Q

what are the penicillinase-resistant penicillins?

A

nafcillin, dicloxacillin, oxacillin

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5
Q

what antimicrobials stop binding of aminoacyl-tRNA to 30S ribosomal subunit?

A

tetracyclines

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6
Q

what species and polymerase/RTase is the preferential target of ganciclovir?

what is different about valganciclovir?

A

CMV DNA polymerase; must be activated by CMV viral kinase

valganciclovir = better oral availability, is prodrug

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7
Q

how does NRTIs affect viral life cycle exactly?

A

incorporation into newly synthesised DNA, but cannot then form 3’-5’ phosphodiester bond to continue DNA replication

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8
Q

why does acyclovir affect HSV/VZV and not CMV/EBV?

A

CMV/EBV lacks the guanosine analog kinase that is needed to activate acylovir (and family) within the infected cell

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9
Q

what are the electrolytes that need monitoring with amphotericin B therapy?

A

K+ and Mg++

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10
Q

rifampin mechanism of action

adverse effects

A

inhibits bacterial DNA-dependent RNA polymerase

red-orange body fluids, cytopenia, GI upset

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11
Q

what is the difference between penicillin G and V?

A

G = IV and IM, V = oral

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12
Q

what advice must be given about taking tetracyclines PO?

A

do not take with milk or antiacids because divalent cations stop gut absorption of these drugs

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13
Q

aminoglycosides are ineffective against what kind of bacteria? why?

A

anaerobes

O2 is required for uptake

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14
Q

what generation are cefazolin and cephalexin? what bugs are they good against?

A

1st generation - PEcK = proteus, E coli, Klebsiella

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15
Q

rocky mountain spotted fever and meningites (H flu, n meningitidis strep pneumo) can all be successfully treated with?

A

chloramphenicol

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16
Q

what is the mechanism of action of terbinafine?

A

inhibits synthesis of ergosterol by inhibiting squalene epoxidase

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17
Q

how does vancomycin resistance occur?

A

in enterococcus by changing cell wall to D-ala-D-lac

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18
Q

what generation are cefaclor, cefoxitin and cefuroxime?what bugs are they good against?

A

2nd generation HENS PEcK = haemophillus, enterobacer, neisseria, serratia PEcK

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19
Q

what are the antipseudomonan penicillins?

A

piperacillin, ticaracillin

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20
Q

what is the indication for sofosbuvir?

A

RNA-dependent RNA polymerase inhibitor specific to hepatitis C

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21
Q

what are the main adverse effects of ganciclovir?

A

bone marrow suppression

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22
Q

what antifungal gives fever and chills upon administration?

does it get better or worse with subsequent administration?

A

amphotericin B

gets better, treatment with antipyretics and antihistamines can ameliorate

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23
Q

other than gram +ve’s, what can you use penicillin for?

A

gram -ve cocci (N meningitidis) and T pallidum spirochetes

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24
Q

what are 3 carbapenems?

A

Imipenem, meropenem, ertapenem

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25
Q

what antibiotics work against chlamydia trachomatis?

A

doxycycline and macrolides (azithromycin erythromycin)

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26
Q

what is the mechanism of action of saquinavir?

A

HIV protease inhibitor - saquinavir

protease coded by pol gene. protease inhibitors stops maturation of new virions

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27
Q

what are the specific fungal species and subcellular structure of griseofulvin?

A

dermatophites

microtubular proteins

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28
Q

what do enfuviride and maraviroc do? how are they different?

A

both HIV fusion blockers.

enfuvirtide - binds gp41 inhibiting viral fusion

maraviroc - blocs CCR5, inhibiting binding with gp120 (docking)

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29
Q

what antibacterials affect which portions of the bacterial ribosome?

A

buy AT 30, CCEL at 50

aminoglycosides, tetracycline - 30S

clindamycin, chloramphenicol, erythromycin (& macrolides), linezolid - 50S

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30
Q

what antiretroviral class gives hyperglycaemia and cushing-like syndrome as side effects?

A

protease inhibitors (-navirs)

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31
Q

what drug blocks peptidyltransferase at the 50S subunit?

A

cholamphenicol

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32
Q

of the penicillinase-sensitive penicillins, which has a greater oral bioavailability?

A

amOxicillin =Orally available

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33
Q

what antibiotics can affect long bone growth in children?

A

tetracyclines

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34
Q

what is red man syndrome and how do you stop it?

A

diffuse erythematous rash wtih vancomycin therapy.

prevent - pre-treat with antihistamine and slow infusion rate

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35
Q

HLA-B 5701 means you cannot give?

what would happen?

A

abacavir (NRTI) in HIV/AIDS treatment

alters MHC I resulting in hypersensitvity reaction (IV) with desquamating rash, GI upset, fever & malaise

36
Q

why is chloroquine ineffective against vivax and ovale in particular?

A

these set up latent infection in the liver.

chloroquine kills plasmodium in the blood but not the exo-erythrocyte phase (liver)

for this treat with primaquine to eradicate hypnozoites

37
Q

what are two distinguishing side effects of cephalosporin?

A
  1. disulphiram reaction with alcohol
  2. vitamin K deficiency
38
Q

3 drugs for MRSA, mechanism of action and side effects

A
  1. vancomycin - binds D-ala-D-ala - red man syndrome, nephrotoxic
  2. daptomycin - pore in membrane - CPK elevation & myopathy
  3. linezolid - binds 50s ribosomal subunit - thrombocytopenia, optic neuritis
39
Q

are antipseudomonals susceptible to penicillinase?

A

yes - ‘pip-taz’.. always give with penicillinase inhibitor

40
Q

what antifungals target the cell wall? the cell membrane?

A

wall = capsofungin

membrane = amphotericin, nystatin (bind ergosterol), -azoles (inhibit synthesis)

41
Q

when is famicyclovir indicated mainly?

A

herpes zoster

42
Q

what does and integrase inhibitor do?

what is the common part of the names to identify these ARVs?

A

inhibit integration of dsDNA to integrate into host cell chromosome, so no new viral mRNA is transcribed

integrase inhibitor = raltegravir, dolutegravir, elvitegravir

43
Q

what is the mechanism of action of oseltamavir and what bug does it work against?

A

inhibits neuraminidase without need for intracellular activation

prevents influenza A/B from exiting the cell

44
Q

in what patient group is doxycycline particularly useful and why?

A

renal failure, faecal excretion

45
Q

how does vancomycin work?

A

binds D-ala-D-ala motif of cell wall precursor

c/o penicillin which acts as decoy D-ala-D-ala

46
Q

what is the mechanism of action of foscarnet?

does this require intracellular activation?

A

foscarnet = pyrofosphate analog

binds & inhibits viral DNA/RNA polymerase and HIV reverse transcriptase

does not require kinase/intracellular activation

47
Q

what must be given with imipenem?

A

cilastatin - inhibitor of renal dehydropeptidase I, slows renal inactivation of the carbapenem

48
Q

are cephalosporins bactericidal or bacteristatic?

A

bactericidal (same mechanism as penicillins)

49
Q

what are the adverse effects of acyclovir and family?

A

obstructive crystalline nephropathy and AKI if not adequately hydrated

50
Q

what is the mechanism of action of acyclovir?

A

nucleoside analog that is activated intracellularly by viral enzyme thymidine kinase - hence few side effects in human tissue

inhibits herpesvirus DNA polymerase

51
Q

what is the mechanism of penicillin resistance in MRSA?

A

mutation of the PBP target site

52
Q

what bugs are killed by extended-spectrum penicillins?

A

HHELPSS haemophilus, H pylori, E coli, Proteus mirablis, Salmonella, Shigella

53
Q

what class is neomycin?

A

aminoglycoside

54
Q

what generation are ceftriaxone, cefotaxime, ceftazidime?

what bugs are they used against?

A

3rd generation - gram negatives resistant to other beta-lactams, cross BBB

ceftriaxone = meningitis, lyme disease, neisseria.

ceftazi​dime = pseudomonas

55
Q

what are the penicillinase inhibitors?

A

claulanic acid, avibactam, sulbactam, tazobactam (CAST)

56
Q

what are the side effects of aminoglycosides?

A

ototoxic, nephrotoxic, neuromuscular blockade

teratogenic

57
Q

what is the mechanism of resistance against tetracyclines?

A

decrease intracellular accumulation by increased efflux or decreased uptake by different drug transporter coded for on a plasmid

58
Q

what is the mechanism of action for acyclovir?

A

inhibitor of viral DNA polymerase

59
Q

what is the mechanism of resistance against acyclovir (& family)

A

mutation of viral thymidine kinase, which is the viral enzyme required for phosphorylation and activation of these nucleoside analogs

60
Q

what is the mechanism of resistance against cephalosporins?

A

structural change of PBPs

61
Q

flattened eggs seen on the perianal tape test are treated with what?

A

bendazoles or pyrantel pamoate

62
Q

nafcillin is useful for what bug?

A

staph aureus

63
Q

what are the adverse effects of vancomycin?

A

NOT without trouble

nephrotoxic, ototoxic, thrombophelbitis

Red man syndrome

64
Q

what is the mechanism of action for cidofovir?

intracellular activation?

indication?

A

inhibits viral DNA polymerase preferentially (still works on human protein a bit though)

no intracellular activation/phosphorylation required

CMV retinitis, acyclovir-resistant HSV

65
Q

what does valacyclovir do better than acyclovir?

A

better oral availability

66
Q

what antibiotics change the colour of your teeth?

A

tetracyclines

67
Q

what medication interferes with bacterial DNA gyrase?

A

quinolones - good against gram-negatives

68
Q

what is the toxicity of cidofovir and how do you get past this?

A

nephrotoxic

administer with probenecid and IV fluids

69
Q

azole antifungals have what effect on P450?

A

inhibit P40

70
Q

what is the mechanism for sulfonamides?

sulfamethoxazole (SMX), sulfisoxazole, sulfadiazine

A

antimetabolite = competes with para-aminobenzoic acid for incorporation into folic acid

71
Q

mechanism of action of isoniazid? side effects?

A

inhibits mycolic acid synthesis

vitamin B6 deficiency, neurotoxic - give with pyridoxine
Hepatotoxic

72
Q

what antimicrobial works through inhibition of arabinosyl transferase?

side effect?

A

ethambutol - optic neuropathy

73
Q

what are the side effects of carbapenems?

A

seizures, GI upset, rash

74
Q

what is a D-Ala-D-Ala analog?

A

penicillin - allows binding of PBPs (transpeptidases)

75
Q

what bugs does ceftaroline cover that other cephalosporins do not? (3)

A

Listeria, MRSA and enterococcus faecalis

5th gen cephalosporin

76
Q

what enzyme is needed to activate isoniazid?

A

intracellular catalase peroxidase

77
Q

what class is streptomycin?

A

aminoglycoside

78
Q

what is an antibiotic good against multi-drug resistant organisms that binds to the 30S subunit of bacterial ribosome

A

Tigecycline - tetracycline derivative

79
Q

what is the benefits of using meropenem rather than other carbapenems? (2)

A

meropenem is resistant to renal dehydropeptidase I and has decreased risk of seizures

80
Q

what generation is cefepime? what is it used for?

A

pseudomonas

81
Q

what is the best drug for tinea corporis, a common dermatophytosis?

A

terbinafine

squalene epoxidase inhibitor

82
Q

what is the main difference between NRTIs and NNRTIs?

A

NNRTIs (delavridine/efavirenz/nevirapine) do not require intracellular activation

83
Q

how does isoniazid cause B6 deficiency?

A

direct hepatocyte damage

84
Q

what class is amikacin?

A

aminoglycoside

85
Q

what are the penicillinase-sensitive penicillins?

A

amox ampicillin aminopenicillins

USMLE S1 (16 decks)

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