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USMLE S1 > Antimicrobials > Flashcards

Antimicrobials Flashcards

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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
what antibiotics work against *chlamydia trachomatis*?
doxycycline and macrolides (azithromycin erythromycin)
26
what is the mechanism of action of saquinavir?
HIV protease inhibitor - saqui**navir** protease coded by *pol* gene. protease inhibitors stops maturation of new virions
27
what are the specific fungal species and subcellular structure of griseofulvin?
dermatophites microtubular proteins
28
what do enfuviride and maraviroc do? how are they different?
both HIV fusion blockers. en**fu**virtide - binds gp41 inhibiting viral **fu**sion maravir**oc** - blocs CCR5, inhibiting binding with gp120 (d**oc**king)
29
what antibacterials affect which portions of the bacterial ribosome?
buy **AT 30**, **CCEL** at **50** aminoglycosides, tetracycline - 30S clindamycin, chloramphenicol, erythromycin (& macrolides), linezolid - 50S
30
what antiretroviral class gives hyperglycaemia and cushing-like syndrome as side effects?
protease inhibitors (-navirs)
31
what drug blocks peptidyltransferase at the 50S subunit?
cholamphenicol
32
of the penicillinase-sensitive penicillins, which has a greater oral bioavailability?
amOxicillin =Orally available
33
what antibiotics can affect long bone growth in children?
tetracyclines
34
what is red man syndrome and how do you stop it?
diffuse erythematous rash wtih vancomycin therapy. prevent - pre-treat with antihistamine and slow infusion rate
35
HLA-B 5701 means you cannot give? what would happen?
abacavir (NRTI) in HIV/AIDS treatment alters MHC I resulting in hypersensitvity reaction (IV) with desquamating rash, GI upset, fever & malaise
36
why is chloroquine ineffective against *vivax* and *ovale* in particular?
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
what are two distinguishing side effects of cephalosporin?
1. disulphiram reaction with alcohol 2. vitamin K deficiency
38
3 drugs for MRSA, mechanism of action and side effects
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
are antipseudomonals susceptible to penicillinase?
yes - 'pip-taz'.. always give with penicillinase inhibitor
40
what antifungals target the cell wall? the cell membrane?
wall = capsofungin membrane = amphotericin, nystatin (bind ergosterol), -azoles (inhibit synthesis)
41
when is famicyclovir indicated mainly?
herpes zoster
42
what does and integrase inhibitor do? what is the common part of the names to identify these ARVs?
inhibit integration of dsDNA to integrate into host cell chromosome, so no new viral mRNA is transcribed in**tegra**se inhibitor = ral**tegra**vir, dolu**tegra**vir, elvi**tegra**vir
43
what is the mechanism of action of oseltamavir and what bug does it work against?
inhibits neuraminidase without need for intracellular activation prevents **influenza A/B** from exiting the cell
44
in what patient group is doxycycline particularly useful and why?
renal failure, faecal excretion
45
how does vancomycin work?
binds D-ala-D-ala motif of cell wall precursor c/o penicillin which acts as decoy D-ala-D-ala
46
what is the mechanism of action of foscarnet? does this require intracellular activation?
foscarnet = pyrofosphate analog binds & inhibits viral DNA/RNA polymerase and HIV reverse transcriptase does not require kinase/intracellular activation
47
what must be given with imipenem?
cilastatin - inhibitor of renal dehydropeptidase I, slows renal inactivation of the carbapenem
48
are cephalosporins bactericidal or bacteristatic?
bactericidal (same mechanism as penicillins)
49
what are the adverse effects of acyclovir and family?
obstructive crystalline nephropathy and AKI if not adequately hydrated
50
what is the mechanism of action of acyclovir?
nucleoside analog that is activated intracellularly **by viral enzyme** thymidine kinase - hence few side effects in human tissue inhibits herpesvirus DNA polymerase
51
what is the mechanism of penicillin resistance in MRSA?
mutation of the PBP target site
52
what bugs are killed by extended-spectrum penicillins?
HHELPSS haemophilus, H pylori, E coli, Proteus mirablis, Salmonella, Shigella
53
what class is neomycin?
aminoglycoside
54
what generation are ceftriaxone, cefotaxime, ceftazidime? what bugs are they used against?
3rd generation - gram negatives resistant to other beta-lactams, cross BBB **ceftriaxone** = meningitis, lyme disease, neisseria. **ceftazi​dime** = pseudomonas
55
what are the penicillinase inhibitors?
claulanic acid, avibactam, sulbactam, tazobactam (CAST)
56
what are the side effects of aminoglycosides?
ototoxic, nephrotoxic, neuromuscular blockade teratogenic
57
what is the mechanism of resistance against tetracyclines?
decrease intracellular accumulation by increased efflux or decreased uptake by different drug transporter coded for on a plasmid
58
what is the mechanism of action for acyclovir?
inhibitor of viral DNA polymerase
59
what is the mechanism of resistance against acyclovir (& family)
mutation of viral thymidine kinase, which is the viral enzyme required for phosphorylation and activation of these nucleoside analogs
60
what is the mechanism of resistance against cephalosporins?
structural change of PBPs
61
flattened eggs seen on the perianal tape test are treated with what?
bendazoles or pyrantel pamoate
62
nafcillin is useful for what bug?
staph aureus
63
what are the adverse effects of vancomycin?
**NOT** without trouble nephrotoxic, ototoxic, thrombophelbitis *Red man syndrome*
64
what is the mechanism of action for cidofovir? intracellular activation? indication?
inhibits viral DNA polymerase preferentially (still works on human protein a bit though) no intracellular activation/phosphorylation required CMV retinitis, acyclovir-resistant HSV
65
what does valacyclovir do better than acyclovir?
better oral availability
66
what antibiotics change the colour of your teeth?
tetracyclines
67
what medication interferes with bacterial DNA gyrase?
quinolones - good against gram-negatives
68
what is the toxicity of cidofovir and how do you get past this?
nephrotoxic administer with probenecid and IV fluids
69
azole antifungals have what effect on P450?
inhibit P40
70
what is the mechanism for sulfonamides? sulfamethoxazole (SMX), sulfisoxazole, sulfadiazine
antimetabolite = competes with para-aminobenzoic acid for incorporation into folic acid
71
mechanism of action of isoniazid? side effects?
inhibits mycolic acid synthesis vitamin B6 deficiency, neurotoxic - give with pyridoxine Hepatotoxic
72
what antimicrobial works through inhibition of arabinosyl transferase? side effect?
ethambutol - optic neuropathy
73
what are the side effects of carbapenems?
seizures, GI upset, rash
74
what is a D-Ala-D-Ala analog?
penicillin - allows binding of PBPs (transpeptidases)
75
what bugs does ceftaroline cover that other cephalosporins do not? (3)
*Listeria,* MRSA and *enterococcus faecalis* 5th gen cephalosporin
76
what enzyme is needed to activate isoniazid?
intracellular catalase peroxidase
77
what class is streptomycin?
aminoglycoside
78
what is an antibiotic good against multi-drug resistant organisms that binds to the 30S subunit of bacterial ribosome
Tigecycline - tetracycline derivative
79
what is the benefits of using meropenem rather than other carbapenems? (2)
meropenem is resistant to renal dehydropeptidase I and has decreased risk of seizures
80
what generation is cefepime? what is it used for?
*pseudomonas*
81
what is the best drug for tinea corporis, a common dermatophytosis?
terbinafine squalene epoxidase inhibitor
82
what is the main difference between NRTIs and NNRTIs?
NNRTIs (delavridine/efavirenz/nevirapine) do not require intracellular activation
83
how does isoniazid cause B6 deficiency?
direct hepatocyte damage
84
what class is amikacin?
aminoglycoside
85
what are the penicillinase-sensitive penicillins?
amox ampicillin aminopenicillins

USMLE S1 (16 decks)

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