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USMLE Step 1 > Microbiology--Pharmacology > Flashcards

Microbiology--Pharmacology Flashcards

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USMLE® Step 1 flashcards
1
Q

Penicillin G ,V use

A

G+ organisms: S pneumoniae, S pyogenes, Actinomyces, Also used for N meningitidis, T pallidum

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2
Q

Ampicillin, amoxicillin use

A

H flu, E coli, Listeria, Proteus, Salmonella, Shigella

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3
Q

Oxacillin, nafcillin, dicloxacillin

A

S aureus–has bulky R group to prevent penicillinase breakdown

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4
Q

antibiotic that can cause pseudomembranous colitis

A

ampicillin, amoxicillin

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5
Q

Ticarcillin, piperacillin

A

antipseudomonals–use with B lactamase inhibitors like tazobactam

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6
Q

what are organisms typically not covered by cephalosporins?

A

LAME: listeria, atypicals (chlamydia, mycoplasma), MRSA, Enterococci

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7
Q

1st generation cephalosporin

A

cefazolin, cephalexin–gram+ and PEcK: proteus, e coli, Klebsiella

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8
Q

2nd generation cephalosporin

A

cefoxitin, cefaclor, cefuroxime–gram +, and HEN PEcKS: h flu, enterobacter, Neisseria spp, Proteus, E coli, Klebsiella, Serratia

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9
Q

3rd generation cephalosporin

A

ceftriaxone, cefotaxime, ceftazidime; use ceftriaxone in meningitis and gonorrhea; use ceftazidime in pseudomonas

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10
Q

4th generation cephalosporin

A

cefepime–increased activity against pseudomonas and G+ organisms

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11
Q

5th generation cephalosporin

A

ceftaroline–broad gram+ and - coverage including MRSA, but does NOT cover pseudomonas

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12
Q

toxicities of cephalosporins?

A

vit K deficiency; low cross reactivity with penicillis; greater nephrotoxicity than aminoglycosides

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13
Q

what is a monobactam?

A

aztreonam–prevents peptidoglycan cross linking by binding to PBP3. Synergistic w/ aminoglycosides; no cross reactivity with penicillin

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14
Q

aztreonam uses?

A

gram - only; no activity against g+ or anaerobes; use in penicillin allergics or renal failure patients who can’t tolerate aminoglycosides

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15
Q

What is imipenem always administered with?

A

cilastatin–inhibitor of renal dehydropeptidase I

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16
Q

Which carbapenem is stable to dehydropeptidase I

A

meropenem

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17
Q

carbapenem tox?

A

GI distress, skin rash, CNS toxicity (seizures)–last resort bug

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18
Q

Vancomycin MoA?

A

inhibits cell wall peptidoglycan formation by binding D-ala Dala portion of cell wall precursors; resistance forms when AA modified to DalaDlac

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19
Q

Vancoymcin use?

A

only for G+, MRSA, enterococci, C diff

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20
Q

Vancomycin tox?

A

NOT; nephrotoxicity, ototoxicity, thrombophlebitis, diffuse flusing (red man syndrome)–prevent with antihistamines and slow infusion rate

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21
Q

Which antibacterial protein synthesis inhibitors target which ribosome?

A

buy AT 30; CCEL at 50: 30S: aminoglycosides, tetracyclines; 50S: chloramphenicol, clindamycin, erythromycin (macrolides), linezolid

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22
Q

What are some aminoglycosides?

A

Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin

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23
Q

aminoglycoside MoA:

A

30S: inhibit formation of initiation complex and cause misreading of mRNA; also blocks translocation; requires O2 for uptake so ineffective against anaerobes

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24
Q

aminoglycoside use?

A

severe gram negative rod infections; synergistic with B lactam anbx; neomycin for bowel surgery;

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25
Q

aminoglycoside resistance?

A

transferase enzymes inactive the drug by acetylation, phophorylation or adenylation

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26
Q

Tetracycline MoA?

A

bind to 30S and prevent attachment of aminoacyl tRNA; limited CNS penetration; doxycycline eliminated by gut and can use in renal failure patients; do not take with milk, antacids, or iron containing preps because divalent cations inhibit gut absorption

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27
Q

Tetracycline use?

A

borrelia, mycoplasma, rickettsia, Chlamydia–drug can accumulate intracellularly

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28
Q

Tetracycline resistance?

A

decreased uptake or increased efflux out of bacterial cells by plasmid encoded transport pumps

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29
Q

Macrolides MoA?

A

Inhibit protein synthesis by blocking translocation; binds to 23S rRNA of 50S ribosomal subunit

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30
Q

Macrolide toxicity?

A

MACRO: GI motility issues, arrhythmia (prolonged QT), acute cholestatic hepatitis, rash, eosinophilia; increases serum concetrations of theophylines, oral anticoagulants

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31
Q

Macrolide resistance?

A

methylation of 23S rRNA-binding site prevents drug binding

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32
Q

Chloramphenicol MoA?

A

blocks peptidyltransferase at 50S ribosomal subunit

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33
Q

Chloamphenicol tox?

A

anemia, aplastic anemia, gray baby syndrome (lack liver UDP-glucuronyl transferase)

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34
Q

Chloramphenicol resistance?

A

plasmid encoded acetyltransferase inactivates the drug

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35
Q

Clindamycin MoA?

A

blocks peptide transfer (translocation) at 50S ribosomal subunit,

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36
Q

Sulfonamide MoA?

A

inhibit folate synthesis, PABA antimetabolites inhibit DHF synthase

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37
Q

Sulfonamides, trimethoprim, pyrimethamine affect the THF pathway at which enzymes?

A

Sulfonamides: Dihydropterate synthase; Trimethoprim/pyramethamine: dihydrofolate reductase

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38
Q

Sulfonamide tox?

A

hemolysis if G6PD deficient; tubulointerstitial nephritis; photosensitivity; kernicterus in infants; displaces other drugs from albumin (like warfarin)

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39
Q

trimethoprim MoA?

A

inhibits DHF reductase

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40
Q

TMP tox?

A

TMP: treats marrow poorly: megaloblastic anemia, leukopenia, granulocytopenia (can alleviate with folinic acid (leucovorin))

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41
Q

Fluoroquinolones (-floxacins)

A

inhibit DNA gyrase (topoisomerase II) and topoisomerase IV; do NOT take with antacids

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42
Q

fluoroquinolone tox?

A

tendonitis/tendon rupture/leg cramps/myalgias, contraindicated in pregnant women, nursing mothers, children < 18 over concerns for cartilage damage, can cause prolonged QT,

43
Q

fluoroquinolone resistance?

A

chromosome encoded mutation in DNA gyrase, plasmid mediated, efflux pumps

44
Q

Metronidazole MoA? Tox?

A

forms free radical toxic metabolites in the bacterial cell that damage DNA; disulfiram like reaction with alcohol; headache; metallic taste

45
Q

Isoniazid MoA?

A

decreases synthesis of mycolic acids, bacterial catalase peroxidase (KatG) needed to convert INH to active metabolite

46
Q

Isoniazid Tx?

A

Neurotoxicity; hepatotoxicity; B6 can prevent neurotoxicity and lupus

47
Q

Rifampin, rifabutin MoA

A

inhibits DNA dependent RNA polymerase

48
Q

Rifabutin is favored in patients w/ HIV over Rifampin why?

A

Rifampin ramps up CYP450; rifabutin does not

49
Q

Pyrazinamide tox?

A

hyperuricemia, hepatotoxicity

50
Q

Ethambutol MoA?

A

decreases carbohydrate polymerization of mycobacterium cell wall by blocking arabinosyltransferase

51
Q

Ethambutol tox?

A

optic neuropathy–can cause red green color blindness

52
Q

Prophylaxis: endocarditis with surgical or dental procedures

A

Penicillins

53
Q

Prophylaxis: gonorrhea

A

ceftriaxone

54
Q

Prophylaxis history of recurrent UTIs

A

TMP SMX

55
Q

Prophylaxis meningococcal infx

A

Ciprofloxacin (rifampin for child)

56
Q

Prophylaxis Pregnant women carrying group B strep

A

Ampicillin

57
Q

Prophylaxis Prevention of gonococcal or chlamydial conjunctivitis in newborn

A

Erythromycin ointment

58
Q

Prevention of postsurgical infection due to S aureus

A

Cefazolin

59
Q

Prophylaxis strep pharyngitis in child with prior rheumatic fever

A

oral penicillin

60
Q

prophylaxis in HIV patients with CD4 counts < 200, <50

A

<50 azithromycin for MAC; use pentamidine if TMPSMX cannot be tolerated

61
Q

serotonin syndrome anbx

A

linezolid–inhibits 50S

62
Q

Amphotericin B MOA?

A

binds ergosterol and forms membrane pores that allow electrolyte leakage

63
Q

what supplements must be given with amphotericin B?

A

supplement K and Mg because of altered renal tubule permeability

64
Q

amphotericin tox?

A

fevers/chills, hypotension, nephrotoxicity, arrhythmias, anemia, IV phelbitis, hydration decreases renal damage; liposomal forms can decrease toxicity

65
Q

Nystatin MoA?

A

binds ergosterol–pores; only topical because so toxic

66
Q

Azoles MoA?

A

inhibit fungal sterol (ergosterol) synthesis by inhibiting CYP450 enymes that convers lanosterol to ergosterol

67
Q

chronic supression of cryptococcal meningitis in AIDS and candida infx of all types

A

fluconazole

68
Q

blastomyces, coccidiodes, histoplasma

A

itraconazole

69
Q

topical fungal infx

A

clotrimazole and miconazole

70
Q

azole tox?

A

testosterone synthesis inhibitor (esp ketoconazole), liver (inhibits CYP450)

71
Q

Flucytosine moA? tox

A

converted to 5-FU via cytosine deaminase to inhibit DNA and RNA biosynthesis; bone marrow supression

72
Q

Caspofungin, micafungin, anidulafungin MoA? Tox?

A

inhibits cell wall synthesis by inhibiting synthesis of B glucan; GI upset/flushing via histamine release

73
Q

Terbinafine MoA? tox?

A

inhibits funal enzyme squalene epoxidase (squalen to squalene epoxide); use for skin funal infections esp finger/toe nails; GI upset/HA/liver tox/taste disturbance

74
Q

Griseofulvin moA? Tox?

A

interferes with microtubule function to disrupt mitosis; teratogenic/carcinogenic/confusion/H/A; increases p450 and warfarin metabolism

75
Q

Chloroquine moA?

A

block detoxification of heme into hemazoin; heme accumulates and kills plasmodia; do not use for falciparum

76
Q

chloroquine resistance?

A

efflux pump

77
Q

falciparum treatment?

A

artemether/lumefantrine, atovaquone/proguanil

78
Q

Zanamivir, oseltamivir moa?

A

neuraminidase inhibitor, prevent release of progeny virus; used for flu A/B

79
Q

ribavirin moa? tox?

A

inhibits synthesis of guanine nucelotides by competitively inhibiting IMP dehydrogenase; RSV/chronic hep C; hemolytic anemia, severe teratogen

80
Q

acyclovir, famciclovir, valacyclovir moa? Tox?

A

guanosine analog that requires phosphorylation by thymidine kinase; used for HSV/VZV; crystalline nephropathy and ARF if not adequately hydrated

81
Q

Ganciclovir moa? Tox?

A

5’ monophosphate formed by CMV viral kinase. Guanosine analog; use for CMV; leukopenia/neutropenia/thrombocytopenia/renal toxicity

82
Q

Foscarnet moa? Tox?

A

viral DNA Polymerase inhibitor that binds to pyrophosphate binding side of enzyme; does not need activation by viral kinase; nephrotoxicity

83
Q

used in CMV retinitis when gancyclovir fails, used in acycolvir resistant HSV

A

foscarnet

84
Q

cidofovir moa, tox?

A

preferentially inhibits viral DNA polymerase; no need for kinase activation; nephrotoxicity, administer with probenecid and IV saline to decrease toxicity

85
Q

when to initiate HAART?

A

aids defining illness, CD4 < 500; high viral load: 2NRTIs and 1 NNRTI/1 protease inhibitor/1 integrase inhibitor

86
Q

-navir HIV drug MoA?

A

protease inhibitors; prevent maturation of new virus;

87
Q

whats special about ritonavir?

A

can boost other drug concentrations by inhibiting P450

88
Q

-navir tox?

A

hyperglycemia, GI intolerance, lipodystrophy, thrombocytopenia

89
Q

tox of indinavir?

A

nephropathy, hematuria

90
Q

NRTIs moa?

A

competitively inhibit nucleotide binding to reverse transcriptase and terminate DNA synthesis (lack 3’ OH group)

91
Q

Tenofovir

A

nucleotide; all others are nucleosides that need to be phosphorylated to be active

92
Q

NRTI tox?

A

bone marrow supression (give GCSF and EPO); peripheral neuropathy; lactic acidosis (nucleosides)

93
Q

NRTI that can cause anemia

A

zidovudine; used in general phrophylaxis and during pregnancy

94
Q

NRTI that causes pancreatitis

A

didanosine

95
Q

NNRTI that causes vivid dreams/CNS symptoms

A

efavirenz

96
Q

NNRTI tox

A

rash and heptotoxicity–do not use delavirdine or efavirenz in pregnancy

97
Q

Raltegravir

A

integrase inhibitor; reversibly inhibits HIV integrase; hypercholesterolemia

98
Q

Enfuvirtide

A

fusion inhibit; binds gp41; inhibits viral entry

99
Q

Maraviroc

A

binds CCR-5 on surface of T cells/monocytes inhibiting interaction with gp120 on HIV

100
Q

IFN-alpha

A

chronic hep B/C, kaposi, hairy cell leukemia, condyloma acuminatum, renal cell carcinoma, malignant melanoma

101
Q

IFN-beta

A

multiple sclerosis

102
Q

IFN gamma

A

chronic granulomatous disease

103
Q

IFN tox?

A

neutropenia, myopathy

104
Q

vitamin A can improve which infection?

A

measles

USMLE Step 1 (36 decks)

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