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NBME Micro > Microbiology: Antimicrobials > Flashcards

Microbiology: Antimicrobials Flashcards

1
Q

What are the antiprotozoal agents of choice for Trypanosoma brucei infection?

A

Suramin, melarsoprol

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2
Q

What are the possible adverse effects of carbapenem class of antibiotics?

A

Carbapenems can cause CNS toxicity and seizures at high plasma levels, GI problems, and skin rash

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3
Q

What 2 common adverse effects of metronidazole are NOT associated with alcohol use?

A

Headache and metallic taste

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4
Q

A patient with AIDS presents with Cushing-like syndrome secondary to use of one of his HIV medications. What is the mechanism of action of the culprit drug?

A

It stops viral maturation by preventing formation of polypeptide products; this is a protease inhibitor “Navir [never] tease a protease”

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5
Q

What is the common renal manifestation of sulfonamide toxicity?

A

Tubulointerstitial nephritis

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6
Q

Which types of organisms are treated with vancomycin?

A

Gram ⊕ only: MRSA, Staphylococcus epidermidis, Enterococcus spp, Clostridium difficile (oral dosing for pseudomembranous colitis)

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7
Q

A patient’s infection is no longer susceptible to tetracycline treatment. What mechanism mediated this resistance?

A

↓ uptake into bacterial cells or ↑ efflux out of cells by plasmid-encoded transport pumps

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8
Q

Why does acyclovir interfere with viral DNA synthesis and not human DNA synthesis?

A

It requires monophosphorylation by the thymidine kinase of herpes simplex virus/varicella-zoster virus and is inactive in uninfected cells

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9
Q

Which processes do sulfonamides and trimethoprim (TMP) affect to exert their antibacterial effects?

A

Folic acid synthesis and reduction (DNA methylation); sulfonamides inhibit PABA to DHF conversion; TMP inhibits conversion of DHF to THF

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10
Q

A patient with well-treated depression has MRSA pneumonia, which is treated with linezolid. Which serious adverse effect might you worry about?

A

Serotonin syndrome; more likely to occur if a patient is also taking a selective serotonin-reuptake inhibitor (due to partial monoamine oxidase [MAO] inhibition)

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11
Q

Name the antifungal agent that deposits in keratin-containing tissues, making it effective against dermatophyte infections.

A

Griseofulvin

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12
Q

A patient being treated for severe multidrug-resistant Eshcerichia coli infection develops slurred speech and weakness. For what other symptoms would you monitor?

A

Nephrotoxicity and respiratory failure; this patient has neurotoxicity from polymyxin use

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13
Q

Nucleoside reverse transcriptase inhibitors (NRTIs) are a class of HIV drugs that inhibit reverse transcriptase. What is a common suffix for this class of drugs?

A

-ine: didanosine, emtricitabine, lamivudine, stavudine, zidovudine; others are abacavir and tenofovir

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14
Q

Macrolides are used to treat infection with which organisms?

A

Gram ⊕ cocci, Mycoplasma, Legionella, Chlamydia, and Bordetella pertussis

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15
Q

Via what receptor does interferon-α act to exert its antiviral effects?

A

The PKR receptor

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16
Q

Acyclovir and valacyclovir are good therapeutic options against herpes simplex virus and varicella-zoster virus. Which common herpes viruses are they not useful against?

A

Epstein-Barr virus (weak activity), cytomegalovirus (no activity)

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17
Q

Deficiency of which enzyme is to blame for premature infants developing gray baby syndrome after receiving chloramphenicol?

A

UDP-glucuronosyltransferase, which premature infants lack

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18
Q

Gynecomastia develops in a man being treated for systemic mycoses. What is the cause of the adverse effect?

A

Inhibition of testosterone synthesis by an azole (most commonly seen with ketoconazole)

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19
Q

Which antifungal drug class kills fungi by causing the formation of membrane pores and disrupting cell membrane integrity?

A

The polyenes (amphotericin B and nystatin)

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20
Q

Which types of influenza are oseltamivir and zanamivir effective against?

A

Influenza A and B (for treatment and prevention)

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21
Q

What is the mechanism of action of isoniazid?

A

↓ synthesis of mycolic acids, which make up the cell wall

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22
Q

What is the activity of acyclovir, famciclovir, and valacyclovir against latent varicella-zoster virus or herpes simplex virus?

A

Minimal; these drugs work best in actively infected cells only

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23
Q

Why are ampicillin and amoxicillin considered extended-spectrum penicillins?

A

They cover Haemophilus influenzae, Helicobacter pylori, Escherichia coli, Listeria monocytogenes, Proteus mirabilis, Salmonella, and Shigella (HHELPSS kill enterococci)

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24
Q

A man has shingles. Which antiviral agent is the most appropriate therapeutic option?

A

Famciclovir (more effective against herpes zoster than acyclovir or valacyclovir)

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25
Q

Which disinfection and sterilization techniques are sporicidal?

A

Autoclaving, chlorine, ethylene oxide, hydrogen peroxide, iodine and iodophors (may be sporicidal)

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26
Q

A patient being treated for malaria complains of blurry vision. What is the most likely cause?

A

Chloroquine-induced retinopathy

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27
Q

What organisms are aminoglycosides used against?

A

Gram ⊖ rods, particularly in cases of severe infection

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28
Q

Antibiotics that target bacteria via their cell walls typically do so by interfering with the production of which cell wall component?

A

Peptidoglycans

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29
Q

What is the mechanism of action of azoles?

A

They block fungal synthesis of sterols (ergosterol) by inhibiting P-450 enzymes from converting lanosterol to ergosterol

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30
Q

Which antifungal drug class works by inhibiting the synthesis of fungal cell walls?

A

The echinocandins (anidulafungin, caspofungin, and micafungin)

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31
Q

What is the mechanism by which bacteria develop resistance to macrolide antibiotics?

A

By methylation of the 23S ribosomal RNA binding site, which prevents the drug from binding to it

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32
Q

Polymyxins are used to treat which types of infections?

A

Last resort treatment for multidrug-resistant gram ⊖ bacterial infections and topical treatment for superficial skin infections

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33
Q

A young woman has chronic hepatitis C and takes an antiviral agent that competitively inhibits IMP dehydrogenase. What are the adverse effects of the antiviral agent she is taking?

A

Hemolytic anemia and severe teratogenicity (the drug is ribavirin)

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34
Q

A patient with a Mycobacterium leprae infection is concerned about infecting family members. What prophylactic agent can you prescribe for them?

A

There is no prophylaxis available for M leprae infection

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35
Q

Sulfonamides are bacteriostatic when used alone but addition of which antibiotic can cause sulfonamides to be bactericidal?

A

Trimethoprim, a dihydrofolate reductase inhibitor

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36
Q

What adverse effects are associated with cephalosporin use?

A

Hypersensitivity reaction, disulfiram-like reaction, autoimmune hemolytic anemia, vitamin K deficiency

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37
Q

A patient who started treatment for lepromatous leprosy presents with sudden-onset cyanosis and hypoxia. What is your diagnosis?

A

Methemoglobinemia; the patient was likely started on dapsone

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38
Q

What monotherapy can be used for chronic hepatitis C infection?

A

None, treatment is always with a combination of drugs

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39
Q

What are some of the adverse reactions associated with vancomycin?

A

Nephrotoxicity, Ototoxicity, Thrombophlebitis (NOT trouble free), red man and DRESS syndromes

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40
Q

A patient taking an antimycobacterial agent has elevated liver enzymes and certain drug interactions. What is the mechanism by which this occurs?

A

Increased cytochrome P-450 activity due to rifampin

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41
Q

After a patient starts therapy for tuberculosis, he notices that his shirt is stained with orange sweat. What is the explanation for this phenomenon?

A

This is a benign adverse effect of Rifampin (Red/orange body fluids)

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42
Q

A woman being treated for mucocutaneous herpes simplex virus develops acute flank pain and nausea. She reports low oral intake due to painful oral lesions. What has happened?

A

She has developed acyclovir-induced obstructive crystalline nephropathy (likely due to inadequate hydration from poor oral intake)

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43
Q

A man’s herpes simplex virus infection does not respond to acyclovir, and he refuses foscarnet due to the seizure risk. What drug can you try next?

A

Cidofovir (given for acyclovir-resistant HSV)

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44
Q

What is the mechanism of resistance to ampicillin and amoxicillin?

A

Bacterial penicillinase cleaves the β-lactam ring (avoid this by coprescribing clavulanic acid, which inhibits penicillinases)

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45
Q

Name 6 antibiotics that can be used to treat methicillin-resistant Staphylococcus aureus (MRSA).

A

Vancomycin, daptomycin, linezolid, tigecycline, ceftaroline, doxycycline

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46
Q

Phlebitis develops in a patient being treated for mucor. Which antifungal agent is the most likely cause?

A

Amphotericin B (“amphoterrible”)

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47
Q

Aztreonam is usually well tolerated, but which adverse effect do patients occasionally have?

A

Gastrointestinal upset

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48
Q

Use of amphotericin B requires supplementation with which electrolytes?

A

Potassium and magnesium (due to altered renal tubule permeability)

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49
Q

Name the 4 carbapenem antibiotics.

A

Doripenem, Imipenem, Meropenem, and Ertapenem (DIME antibiotics are given when there is a 10/10 [life-threatening] infection)

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50
Q

What is the mechanism of action of the rifamycins, rifabutin and rifampin?

A

They block mRNA synthesis via inhibition of DNA-dependent RNA polymerase

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51
Q

What 2 adverse effects are caused by efavirenz?

A

CNS symptoms and vivid dreams

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52
Q

What is the advantage of using valacyclovir over acyclovir?

A

Valacyclovir is a prodrug of acyclovir with better oral bioavailability

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53
Q

Addition of a certain bactericidal antibiotic leads to misreading of the mRNA. Inhibition of which ribosomal subunit is likely the cause?

A

30S ribosomal unit (blocked by aminoglycosides and can cause misreading of mRNA)

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54
Q

A premature infant in Western Africa develops grayish skin after receiving a certain antibiotic. What is the mechanism of action of the antibiotic given?

A

Inhibits peptidyltransferase activity in the 50S subunit of the ribosome; the drug administered was chloramphenicol

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55
Q

How does adjusting the dose of the antibiotic chloramphenicol influence its risk of causing anemia?

A

Lowering the dose will lower the risk of anemia, as chloramphenicol-induced anemia is a dose-dependent adverse effect of the drug

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56
Q

Which antifungal agent is primarily used to treat onychomycosis?

A

Terbinafine

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57
Q

How do bacteria develop resistance to vancomycin?

A

Conversion of D-Ala-D-Ala to D-Ala-D-Lac; (if you Lack a D-Ala (dollar), you can’t ride the van [vancomycin])

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58
Q

What is the most serious adverse effect of flucytosine?

A

Bone marrow suppression

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59
Q

How does daptomycin exert its antibacterial effects?

A

It interferes with membrane integrity

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60
Q

A patient with renal failure needs a tetracycline-class drug for treatment of a Mycoplasma pneumoniae infection. What do you prescribe and why?

A

Doxycycline; it is fecally eliminated and can be used by patients with renal failure

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61
Q

A patient in renal failure needs to start antiretroviral therapy (ART) for newly diagnosed HIV. Which protease inhibitor should not be given to him?

A

Indinavir, which can cause nephropathy and hematuria

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62
Q

What are some of the dermatological manifestations of sulfonamide toxicity?

A

Photosensitivity or Stevens-Johnson syndrome

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63
Q

Clindamycin is used to treat anaerobic infections above the diaphragm. Which antimicrobial is used to treat infections below the diaphragm?

A

Metronidazole

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64
Q

What advantage does the prodrug of ganciclovir have?

A

Better oral bioavailability; the prodrug is valganciclovir

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65
Q

What is the mechanism of action of cidofovir?

A

Inhibits viral DNA polymerase; unlike guanosine analogs, it does not require phosphorylation by viral kinases

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66
Q

The peptidyl transferase activity is ↓ in bacteria after having given a certain 50S-inhibiting antibiotic. Identify the antibiotic.

A

Chloramphenicol

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67
Q

What is the mechanism of action of fluoroquinolones?

A

They inhibit prokaryotic topoisomerase II (DNA gyrase) and topoisomerase IV; they are bactericidal

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68
Q

Name the peptidoglycan cross-linking, inhibiting antibiotics that are penicillinase sensitive.

A

Penicillin G and V, ampicillin, amoxicillin

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69
Q

At what point during disease progression is imipenem or meropenem considered?

A

When other medications have failed or in life-threatening infections; they have significant adverse effects

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70
Q

Name the 4 non-respiratory fluoroquinolones.

A

Ciprofloxacin, norfloxacin, ofloxacin, and enoxacin

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71
Q

Describe the mechanism of action of the bacteriostatic macrolide antibiotics.

A

They inhibit protein synthesis by binding to the 23S rRNA of the 50S subunit and preventing translocation (macroslides)

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72
Q

An HIV antiviral drug prevents viral penetration. This ultimately blocks which genetic process immediately downstream of penetration?

A

Uncoating and reverse transcription (the drug is the fusion inhibitor enfuvirtide)

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73
Q

You treat a patient with an extended-spectrum β-lactam for a pseudomonal infection. What must be coadministered to overcome antibiotic resistance?

A

A β-lactamase inhibitor

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74
Q

A patient being treated for tinea corporis complains of headache and confusion. What is the most likely cause?

A

Griseofulvin

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75
Q

What is the general indication for treatment or prophylaxis with azoles?

A

For local and less serious systemic mycoses

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76
Q

How do penicillins, antipseudomonals, cephalosporins, carbapenems, and monobactams work?

A

They block cell wall synthesis by inhibiting cross-linking of peptidoglycans

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77
Q

What is the common dermatologic adverse effect of fluoroquinolones?

A

Rash

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78
Q

How does the antifungal drug that inhibits squalene epoxidase affect the concentration of ergosterol?

A

It will ↓ the level of ergosterol by ↓ lanosterol concentration available for 14-α-demethylase to convert into ergosterol

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79
Q

What are some potential adverse effects of daptomycin?

A

Rhabdomyolysis, myopathy

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80
Q

What antibiotic classically causes gray baby syndrome if taken by a pregnant woman?

A

Chloramphenicol

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81
Q

Contrast the modes of administration for penicillin G and penicillin V.

A

Penicillin G is administered intravenously or intramuscularly; penicillin V is administered orally

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82
Q

A man with sepsis receiving an aminoglycoside shows worsening renal function after receiving another drug. Which drug was added?

A

A cephalosporin (when combined with aminoglycosides, cephalosporins ↑ the potential for nephrotoxicity)

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83
Q

What are the 3 major adverse effects of ampicillin and amoxicillin?

A

Rash, hypersensitivity reaction, pseudomembranous colitis

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84
Q

Aztreonam is active against which organisms?

A

Gram ⊖ rods only

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85
Q

What is the mechanism of action of permethrin?

A

Blockage of sodium channels leading to depolarization of the neuronal membrane

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86
Q

A mutation in which enzyme allows cytomegalovirus and herpes simplex virus to be resistant to foscarnet?

A

DNA polymerase

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87
Q

A man’s cytomegalovirus infection is noted to have mutated viral kinases on genetic analysis. How does this influence the use of foscarnet as a treatment?

A

It has no influence; foscarnet does not require activation by viral kinases, and its efficacy will not be affected

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88
Q

What antifungal drug class works by inhibiting ergosterol synthesis?

A

Azoles (clotrimazole, fluconazole, itraconazole, ketoconazole, miconazole, and voriconazole)

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89
Q

Which aspect of nafcillin makes it resistant to degradation by the bacterial β-lactamase?

A

Bulky R group blocks access of β-lactamase to the β-lactam ring of the antibiotic

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90
Q

What are the 2 adverse effects of echinocandins?

A

Gastrointestinal upset and flushing

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91
Q

Which organisms are covered by the first-generation cephalosporins?

A

Gram ⊕ cocci (such as Staphylococcus auerus), Proteus mirabilis, Eschericia coli, Klebsiella pneumoniae (⊕ PEcK)

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92
Q

A patient receiving a new HIV drug regimen has had several skin reactions at the site of injection. What drug was she prescribed?

A

Enfuvirtide

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93
Q

Name the drug that is a monobactam.

A

Aztreonam

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94
Q

A patient has a severe gram ⊖ organism infection. Why do you choose to treat with aminoglycosides and a monobactam?

A

Aztreonam, a monobactam, is synergistic with aminoglycosides

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95
Q

A patient has a Sarcoptes scabiei infection. Which anti-mite/louse agents may be used?

A

Treat PML (Pesty Mites and Lice) with PML (Permethrin, Malathion, Lindane) because they NAG you (Na, AChE, GABA blockade)

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96
Q

Name the 2 fungal infections that are treated with isavuconazole?

A

Serious Aspergillus or Mucor infections

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97
Q

A man presents with low hemoglobin soon after starting on sulfadiazine. Which underlying enzyme deficiency does he likely have?

A

G6PD deficiency, causing hemolytic anemia

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98
Q

Name the 2 antibiotics that belong to the polymyxin class.

A

Colistin (polymyxin E) and polymyxin B

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99
Q

A patient with otitis externa is on an antibiotic that inhibits DNA gyrase. By what mechanisms can the bacteria develop resistance to the drug?

A

Chromosome-encoded mutation in the bacterial DNA gyrase, efflux pumps, or resistance mediated by plasmids; the patient is on a fluoroquinolone

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100
Q

What is the difference between disinfection and sterilization?

A

Disinfection reduces the number of pathogenic organisms to a safe level; sterilization inactivates all microbes (including spores)

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101
Q

What is the mechanism of action of dapsone?

A

It inhibits dihydropteroate synthase (sulfonamides inhibit the same enzyme), impairing bacterial folate synthesis

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102
Q

A man has a severe gram ⊖ infection that has been resistant to previously prescribed β-lactams. What do you prescribe next?

A

A third-generation cephalosporin (ceftriaxone, cefotaxime, cefpodoxime, or ceftazidime)

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103
Q

Which drug treats hepatitis C virus (HCV) by inhibiting HCV RNA-dependent RNA polymerase?

A

Sofosbuvir or dasabuvir (both cause viral RNA chain termination)

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104
Q

What is the mechanism of action of pyrazinamide?

A

Unclear; it acts via an unknown mechanism intracellularly

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105
Q

While prescribing antiretroviral therapy (ART), you discover that your patient has an HLA-B*5701 mutation. What drug is contraindicated?

A

Abacavir (nucleoside reverse transcriptase inhibitor [NRTI]) due to the ↑ risk of hypersensitivity

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106
Q

What is the mechanism of action of the antifungal agent terbinafine?

A

It inhibits squalene epoxidase (converts squalene into squalene epoxide), which ultimately blocks the production of lanosterol

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107
Q

When drug X, which is metabolized by P-450, is given to patients on treatment for tuberculosis, the serum levels are higher than expected. Identify the culprit.

A

Isoniazid; it is an inhibitor of cytochrome P-450

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108
Q

What is the mechanism by which bacteria develop resistance to aminoglycosides?

A

Transferase enzymes inactivate the drug by acetylation, phosphorylation, or adenylation

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109
Q

Which antibiotic is given to newborns as prophylaxis against gonococcal conjunctivitis?

A

Erythromycin ointment applied to the eyes

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110
Q

What is the mechanism of action of maraviroc?

A

Binds CCR-5 on T cells/monocytes, inhibiting CCR-5 interaction w/gp120; (maraviroc inhibits docking)

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111
Q

For hepatitis C infections refractory to newer therapies, what agent can be administered as an adjunct?

A

Ribavirin

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112
Q

Name 2 antibiotics that can be used against multidrug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii.

A

Polymyxins B and E (colistin)

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113
Q

How does resistance to acyclovir occur?

A

Mutated viral thymidine kinase

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114
Q

How are sulfonamides and dapsone similar?

A

They both inhibit folate synthesis by blocking dihydropteroate synthase

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115
Q

Name an antifungal agent that works by inhibiting nucleic acid synthesis.

A

Flucytosine

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116
Q

A drug is added to influenza-infected cells. Formed viral progeny become trapped within the cell. This is due to inhibition of which enzyme?

A

Neuraminidase (the drug is likely a neuraminidase inhibitor, such as oseltamivir or zanamivir, which blocks progeny virus release from the cell)

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117
Q

A patient taking an intravenous antibiotic for Clostridium difficile notices a metallic taste. Which antibiotic is it?

A

Metronidazole

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118
Q

What is the common gastrointestinal adverse effect of fluoroquinolones?

A

Gastrointestinal upset

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119
Q

A patient experiences taste disturbances after being treated for a fungal infection of his toenails. What is the drug’s mechanism of action?

A

Inhibits squalene epoxidase (in fungi)

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120
Q

What are the potential adverse effects of tigecycline?

A

Gastrointestinal distress, including nausea and vomiting

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121
Q

What is the mechanism by which bacteria develop resistance to carbapenems?

A

Via carbapenemases, typically produced by Klebsiella pneumoniae, Eshcerichia coli, and Enterobacter aerogenes

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122
Q

A pregnant woman is found to be HIV ⊕ and asks about drug options to help protect her child. Which nucleoside reverse transcriptase inhibitor (NRTI) may be used?

A

Zidovudine (ZDV) can ↓ the risk of vertical transmission and is also used for general prophylaxis

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123
Q

Why is daptomycin ineffective against MRSA pneumonia?

A

Daptomycin binds to and is inactivated by surfactant before it can act on the lungs

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124
Q

How does adjusting the dose of the antibiotic chloramphenicol influence its risk of causing pancytopenia?

A

It has no effect because aplastic anemia is a dose-independent adverse effect of chloramphenicol

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125
Q

What is the mechanism of action of malathion?

A

It inhibits mite/louse acetylcholinesterases

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126
Q

Name 5 antibiotics that work by binding to the bacterial 50S ribosomal subunits and blocking protein synthesis.

A

Chloramphenicol, clindamycin, streptogramins (quinupristin/dalfopristin), linezolid, macrolides (azithromycin/clarithromycin/erythromycin)

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127
Q

A man on gentamicin is recently started on a new medication. He soon develops hearing loss. Which drug was added?

A

Likely a loop diuretic, which ↑ the ototoxic potential of aminoglycosides

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128
Q

What is the major reason for the limited use of chloramphenicol in the United States?

A

High level of toxicity (although still widely used in developing countries due to low cost)

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129
Q

What is the mechanism of action of the anti-hepatitis C virus drugs simeprevir and grazoprevir?

A

Inhibition of HCV protease (NS3/4A), thereby preventing viral replication

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130
Q

A patient taking a β-lactam drug with reduced penicillinase susceptibility develops a prolonged prothrombin time. Why?

A

Cephalosporin use can lead to vitamin K deficiency, leading to ↓ clotting factors

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131
Q

A patient being treated with clindamycin develops pseudomembranous colitis. How did this happen?

A

Clindamycin kills normal gut bacterial flora and allows for the overgrowth of Clostridium difficile

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132
Q

What is the mechanism of action of the drug of choice for non-falciparum malaria?

A

Blockage of detoxification of heme into hemozoin, causing accumulation of heme, which is toxic to Plasmodium; the drug is chloroquine

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133
Q

A patient starts treatment for CMV with a guanosine analog. Soon after, blood tests show a rising BUN and creatinine. What is the most likely cause of these lab findings?

A

Ganciclovir-induced renal toxicity

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134
Q

Which anti-malarial agents should be administered to patients with life-threatening malaria infections?

A

Quinidine in the US (quinine in other countries) or artesunate

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135
Q

Aminoglycosides are synergistic w/which class of antibiotics?

A

β-lactams

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136
Q

What prophylactic antibiotic is used for patients with prosthetic heart valves undergoing dental procedures?

A

Amoxicillin; for patients with high risk for endocarditis

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137
Q

A 55-year-old man with epilepsy is started on ciprofloxacin for a UTI. Why might this be a potential problem?

A

Most antiepileptics are metabolized by the cytochrome P-450 system, which is inhibited by ciprofloxacin

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138
Q

Why are trimethoprim and sulfamethoxazole used in combination?

A

To synergistically inhibit folate metabolism and thus DNA synthesis, leading to bacterial death instead of growth suppression

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139
Q

A patient taking prednisone is given an antibiotic and develops tendon rupture as a complication. What abnormal finding might you see on his ECG?

A

A prolonged QT interval; the antibiotic given was a fluoroquinolone, which may cause tendon rupture when combined with prednisone

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140
Q

A 35-year-old hiker from Connecticut has a “bulls-eye” rash on his arm. You prescribe an antibiotic and caution him against consuming what?

A

Milk, antacids, and iron-containing products; divalent cations inhibit the absorption of tetracyclines

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141
Q

A patient being treated for ringworm experiences flushing, tachycardia, and hypotension after a bachelor party. What drug interaction occurred?

A

Alcohol, and griseofulvin caused a disulfiram-like reaction

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142
Q

Name the 3 respiratory fluoroquinolones.

A

Levofloxacin, moxifloxacin, and gemifloxacin

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143
Q

Which feature of tetracyclines makes them effective against Rickettsia and Chlamydia infections?

A

Their ability to accumulate intracellularly

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144
Q

What is the mechanism of action of cephalosporin antibiotics?

A

They are bacteriocidal β-lactams that inhibit cell wall synthesis

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145
Q

What are the 3 different mechanisms by which bacteria develop resistance against sulfonamides?

A

Altered bacterial dihydropteroate synthase, ↓ uptake, or ↑ PABA synthesis

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146
Q

A patient has liver dysfunction after being treated for an Aspergillus infection. What is the mechanism for liver dysfunction?

A

Azoles inhibit cytochrome P-450

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147
Q

You prescribe metronidazole and advise the patient to avoid alcohol use. Why?

A

Metronidazole with alcohol causes a disulfiram-like reaction (severe flushing, hypotension, tachycardia)

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148
Q

What is unique regarding the presentation of seizures induced by isoniazid toxicity?

A

Seizures caused by isoniazid toxicity are refractory to benzodiazepines

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149
Q

What is the mechanism of action of aminoglycosides?

A

They are bactericidal antibiotics that irreversibly inhibit the initiation complex by binding 30S, blocking translocation, and causing misreading of mRNA

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150
Q

A woman was prescribed an antibiotic during pregnancy. Her baby has hearing abnormalities as a result. Which class of drug was it?

A

An aminoglycoside

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151
Q

What is the mechanism of action of ampicillin and amoxicillin?

A

Blockage of bacterial cell wall synthesis through inhibition of peptidoglycan cross-linking (same as penicillin)

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152
Q

What are the adverse effects associated with pyrazinamide?

A

Hyperuricemia and hepatotoxicity

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153
Q

Which process does rifampin block to exert antimicrobial effects?

A

The synthesis of bacterial messenger RNA (mRNA) via inhibiting RNA polymerase

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154
Q

Why do patients require different dosages of isoniazid?

A

People are either fast or slow acetylators, and the half-life of isoniazid differs depending on the individual rate of acetylation

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155
Q

What is key for zanamivir and oseltamivir to be effective in shortening the duration of influenza symptoms?

A

Initiation of therapy within 48 hours of symptom onset

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156
Q

A patient with a severe bacterial infection is allergic to penicillin. Are monobactams a good treatment option?

A

Yes; aztreonam has no cross-sensitivity to penicillins/aminoglycosides and is usually nontoxic, making it a reasonable choice

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157
Q

What is the mechanism of action of griseofulvin?

A

Inhibition of microtubule function, thereby disrupting mitosis

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158
Q

A patient falls gravely ill with meningococcal meningitis. What do you give close contacts for prophylaxis?

A

Ceftriaxone, ciprofloxacin, or rifampin

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159
Q

A patient is given a triple antibiotic ointment for a superficial skin infection. Which antibiotic in the topical therapy is a cationic polypeptide?

A

Polymyxin B

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160
Q

Which antibiotic targeting bacterial protein synthesis can be given prophylactically before bowel surgery?

A

Neomycin (an aminoglycoside)

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161
Q

What is the mnemonic to remember for which protein synthesis inhibitors affect which bacterial ribosome subunits?

A

Buy AT 30, CCEL (sell) at 50: Aminoglycosides, Tetracyclines (30S); Chloramphenicol, Clindamycin, Erythromycin, Linezolid (50S)

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162
Q

A patient being treated for HIV is noted to have an ↑ creatine kinase level. What is the most likely cause?

A

An integrase inhibitor (eg, elvitegravir, dolutegravir)

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163
Q

What is the mechanism of action of caspofungin?

A

Inhibition of β-glucan synthesis, which disrupts cell wall synthesis

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164
Q

A child presents with discolored teeth, inhibited bone growth, and gastrointestinal distress secondary to antibiotic treatment. What is the antibiotic used?

A

A tetracycline, which should be avoided in children because of these adverse effects

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165
Q

Which carbapenem has limited Pseudomonas coverage?

A

Ertapenem

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166
Q

What are the common CNS adverse effects of fluoroquinolones?

A

Headaches, dizziness

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167
Q

What biochemical variation in MRSA makes nafcillin ineffective?

A

Alteration of the penicillin-binding protein target site

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168
Q

What is the mechanism of action of clindamycin?

A

It is a bacteriostatic antibiotic that inhibits peptide transfer (translocation) at the 50S ribosomal subunit

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169
Q

Which topical antifungal agent might you prescribe for vaginal candidiasis?

A

Topical nystatin

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170
Q

A patient who is HIV ⊕ and receiving antiretroviral therapy (ART) presents with heavy nosebleeds, bruising, hematuria and thrombocytopenia. What drug is the culprit?

A

Indinavir; this protease inhibitor causes thrombocytopenia, nephropathy and hematuria

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171
Q

What is the mechanism of action of daptomycin?

A

Creates transmembrane channels that disrupt cell membranes of gram ⊕ cocci

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172
Q

Describe the mechanism of action for sulfonamide antibiotics

A

They prevent folate synthesis by inhibiting dihydropteroate synthase, and in doing so, prevent bacterial replication (bacteriostatic)

173
Q

What drug should not be taken with fluoroquinolones?

A

Antacids

174
Q

What types of infections are the echinocandins used to treat?

A

Invasive aspergillosis, Candida infections

175
Q

What is autoclaving?

A

An infection control technique that involves the use of pressurized steam at temperatures >120°C; this effect may be sporicidal

176
Q

Acyclovir, famciclovir, and valacyclovir are guanosine analogs activated by viral thymidine kinase. What viral enzyme do they inhibit?

A

Viral DNA polymerase through chain termination

177
Q

Which 2 azoles are commonly used to treat topical fungal infections?

A

Clotrimazole and miconazole

178
Q

What are some adverse effects of penicillinase-resistant penicillins?

A

Hypersensitivity reaction and interstitial nephritis

179
Q

Name the 2 drugs that belong to the rifamycin class of antibiotics.

A

Rifampin and rifabutin

180
Q

Why is rifampin used with dapsone for the treatment of leprosy?

A

It delays the development of resistance to dapsone

181
Q

Amphotericin B is used to treat which specific fungal infections?

A

Serious systemic mycoses such as Cryptococcus, Blastomyces, Coccidioides, Histoplasma, Candida, Mucor

182
Q

A patient with an itchy scalp is found to have lice. Which anti-mite/louse agents may be used?

A

Treat PML (Pesty Mites and Lice) with PML (Permethrin, Malathion, Lindane) because they NAG you (Na, AChE, GABA blockade)

183
Q

How does the microbial coverage of ampicillin compare to that of penicillin?

A

Ampicillin and amoxicillin have a broader spectrum of coverage (AMinoPenicillins are AMPed-up penicillin)

184
Q

Why should clarithromycin be avoided in pregnant mothers with infections?

A

It is embryotoxic

185
Q

What neurologic injury can sulfonamides cause in infants?

A

Kernicterus

186
Q

What are the adverse effects of penicillin?

A

Hypersensitivity reactions, drug-induced interstitial nephritis, and direct Coombs ⊕ hemolytic anemia

187
Q

What are the first-line antiviral agents used to treat herpes simplex virus infections?

A

Acyclovir, valacyclovir, famciclovir

188
Q

A 16-year-old teenager with acne has a chlamydial infection. Why is your antibiotic of choice a tetracycline?

A

Tetracyclines treat both Chlamydia and acne

189
Q

Name the peptidoglycan cross-linking, inhibiting antibiotics that are penicillinase resistant.

A

Oxacillin, naficillin, dicloxacillin

190
Q

A patient on anidulafungin experiences skin flushing. What is the mechanism by which the drug causes this adverse effect?

A

Release of histamine

191
Q

Penicillin is a D-Ala-D-Ala analog. What is its mechanism of action?

A

Binds transpeptidases (penicillin-binding proteins) and impairs cross-linking of peptidoglycan cell wall; also activates autolytic enzymes

192
Q

What is the antiprotozoal agent of choice for leishmaniasis?

A

Sodium stibogluconate

193
Q

A patient being treated for HIV is receiving a nucleoside reverse transcriptase inhibitor (NRTI) that does not require intracellular phosphorylation. What drug is this?

A

Tenofovir, which is already a nucleoTide; all other NRTIs require phosphorylation

194
Q

A neonate has severe jaundice and no startle (Moro) reflex. Which antibiotic might his mother have taken during pregnancy?

A

A sulfonamide, which can cause kernicterus in the newborn

195
Q

What is the effect of griseofulvin on the cytochrome P-450 system?

A

It is an inducer, resulting in ↑ cytochrome P-450 activity

196
Q

Which azole should be used to prevent cryptococcal meningitis and Candida infections (any type) in patients with AIDS?

A

Fluconazole

197
Q

What is the treatment for lepromatous leprosy?

A

Long-term regimen of dapsone, rifampin, and clofazimine

198
Q

What is the mechanism of action of vancomycin?

A

It binds the D-Ala D-Ala part of cell wall precursors, thereby inhibiting the formation of peptidoglycan cell wall

199
Q

What are 2 ways to reduce the toxicity of amphotericin B?

A

Use the liposomal formulation of the drug and hydrate to prevent nephrotoxicity

200
Q

Drug Y is added to HIV-infected cells and this prevents transcription of HIV DNA by inhibiting HIV genome integration to the host cell. What category of drug was added?

A

An integrase inhibitor (dolutegravir, elvitegravir, raltegravir), which reversibly blocks viral DNA integration into host cell genome for transcription

201
Q

A patient with COPD and a recent episode of pneumonia has ↑ serum levels of theophylline. Which antibiotic is he likely taking?

A

A macrolide

202
Q

A patient with AIDS is started on dapsone for Pneumocystis jirovecii prophylaxis. Soon after, he develops a hemolytic crisis. Why?

A

Dapsone causes hemolysis in patients who are G6PD deficient

203
Q

For which specific infections should the azole itraconazole be used to treat?

A

Blastomyces, Coccidioides, Histoplasma, or Sporothrix schenckii

204
Q

What are the adverse effects associated with piperacillin and ticarcillin?

A

Hypersensitivity reactions

205
Q

A pregnant woman being treated for HIV develops anemia. Which drug is responsible?

A

Zidovudine (ZDV)

206
Q

How do bacteria develop resistance to penicillin?

A

By developing β-lactamases, such as penicillinase, which cleaves the β-lactam ring, or by direct mutations in the penicillin-binding proteins

207
Q

Which infections is β-lactam ceftriaxone most effective against?

A

Meningitis, disseminated Lyme disease, gonorrhea

208
Q

For which indications is cidofovir commonly used?

A

Cytomegalovirus retinitis in immunocompromised patients, acyclovir-resistant herpes simplex virus infections

209
Q

How would an organism become resistant to linezolid?

A

From a point mutation in the ribosomal RNA

210
Q

Name an antibiotic in the glycylcycline class.

A

Tigecycline

211
Q

Are patients with penicillin allergies allergic to cephalosporins?

A

Cephalosporins have some cross-sensitivity with penicillins

212
Q

What are the clinical uses of fluoroquinolones?

A

Treat gram ⊖ rods causing urinary and gastrointestinal tract infections (including Pseudomonas), some gram ⊕ organisms, and otitis externa

213
Q

What is the mechanism of action of metronidazole for its antimicrobial effect?

A

Free radical-induced damage to DNA integrity

214
Q

Name the agents that can be used to treat helminthic infections.

A

Pyrantel pamoate, Ivermectin, Mebendazole, Praziquantel, Diethylcarbamazine (helminths get PIMP’D)

215
Q

Which bacterial species are targeted by ticarcillin and piperacillin?

A

Pseudomonas spp and gram ⊖ rods

216
Q

A health care worker exposed to Mycobacterium tuberculosis is given the prophylactic drug, isoniazid. Which bacterial enzyme is needed for it to become active?

A

Catalase-peroxidase (encoded by KatG) converts isoniazid to its active form

217
Q

Name 4 examples of second-generation cephalosporins.

A

Cefaclor, Cefoxitin, cefuroxime, and cefotetan (2nd graders wear fake fox fur to tea parties)

218
Q

An man with HIV develops CMV esophagitis. He starts anti-CMV therapy. Soon after, he exhibits leukopenia, neutropenia, and thrombocytopenia. What likely caused the cytopenias?

A

He most likely began ganciclovir therapy for the CMV esophagitis and developed bone marrow suppression as an adverse effect

219
Q

A man receives an antibiotic for vancomycin-resistant enterococcus. He notes tingling and decreased sensation in his hands. What is the antibiotic’s mechanism of action?

A

Binds to the 50S subunit and blocks formation of the initiation complex, inhibiting protein synthesis; this is neuropathy from linezolid

220
Q

A patient taking antiretroviral therapy (ART) for HIV has nausea, diarrhea, lipodystrophy, and episodes of hyperglycemia. Which class of drug is she likely taking?

A

An HIV protease inhibitor

221
Q

What is the adverse effect of cidofovir, and how can it be prevented?

A

Nephrotoxicity; coadministration with probenecid and IV saline solution

222
Q

Which antifungal agent acts like amphotericin B but is only available in topical formulations because of systemic toxicity

A

Nystatin (same mechanism as amphotericin B)

223
Q

Antibiotics that target bacterial ribosomes typically do so by targeting which 2 ribosomal components?

A

The 30S subunit and the 50S subunit

224
Q

The big toe of a patient being treated for tuberculosis becomes red, swollen, and painful. Which antimycobacterial agent is the most likely cause?

A

Pyrazinamide, which can induce hyperuricemia

225
Q

Which class of antibiotics should pregnant women avoid to prevent discoloration of teeth and abnormal bone growth in their children?

A

Tetracyclines

226
Q

Which third-generation cephalosporin is effective against Pseudomonas infections?

A

Ceftazidime

227
Q

Why are aminoglycosides ineffective against anaerobes?

A

They require oxygen for uptake

228
Q

Which antibiotics should be avoided in pregnancy?

A

Sulfonamides, Aminoglycosides, Fluoroquinolones, Clarithromycin, Tetracyclines, Ribavirin, Griseofulvin, Chloramphenicol (SAFe Children Take Really Good Care)

229
Q

You add a bacteriostatic antibiotic to bacteria and notice that the A-site tRNA binding is reduced. Which ribosomal subunit is inhibited?

A

30S (this is caused by tetracycline antibiotics)

230
Q

Which organisms would you consider using linezolid against?

A

Gram ⊕ organisms, including MRSA and vancomycin-resistant enterococcus (VRE)

231
Q

A patient with active tuberculosis is found to be HIV ⊕. How must his treatment regimen for either diagnosis be modified?

A

Rifampin causes potent CYP/UGT induction that ↓ protease inhibitor levels; it should be replaced with rifabutin

232
Q

Use of aminoglycoside antibiotics is absolutely contraindicated in patients with what disorder?

A

Myasthenia gravis

233
Q

What dermatologic adverse effect results from use of tetracyclines?

A

Photosensitivity

234
Q

Name the carbapenem that is resistant to β-lactamase and is prescribed with cilastatin to prevent inactivation by the kidneys

A

Imipenem, a broad-spectrum antibiotic (“the kill is lastin’ with cilastatin”)

235
Q

A patient with herpes simplex virus is believed to have a strain resistant to acyclovir. Which pyrophosphate analog should be considered?

A

Foscarnet

236
Q

When would you consider using clindamycin over metronidazole to treat an anaerobic infection?

A

Clindamycin is useful for anaerobic infections above the diaphragm; metronidazole, for those below it

237
Q

Name 3 antibiotics that belong to the tetracycline class of antibiotics.

A

Tetracycline, doxycycline, and minocycline

238
Q

What is the mechanism of resistance to cephalosporins?

A

Via inactivation by cephalosporinases (a type of β-lactamase) or by structural changes in the penicillin-binding proteins (transpeptidases)

239
Q

A patient is found to have drug-induced systemic lupus erythematosus (SLE) after completing prophylaxis for tuberculosis. Which drug is the most likely cause?

A

Isoniazid

240
Q

Neuraminidase inhibitors are used to treat which viral infections?

A

Influenza A and B infections (neuraminidase inhibitors: eg, oseltamivir, zanamivir)

241
Q

What is the binding site for foscarnet?

A

The pyrophosphate-binding site of either viral DNA/RNA polymerase or HIV reverse transcriptase (foscarnet = pyrofosphate analog)

242
Q

What is the first-choice antiviral agent for an immunocompromised patient with cytomegalovirus retinitis?

A

Ganciclovir

243
Q

A woman was given an antibiotic during pregnancy, and her baby has cartilage damage as a result. Which class of drug was it?

A

A fluoroquinolone

244
Q

Name 5 antibiotics that belong to the aminoglycoside class of antibiotics.

A

Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin; “Mean” (aminoglycosides) GNATS

245
Q

What is the mechanism of action of ethambutol?

A

Ethambutol blocks arabinogalactan synthesis (via arabinosyl transferase inhibition) in the mycobacterial cell wall

246
Q

Which antimycobacterial agents can be used for meningococcal prophylaxis?

A

Rifampin, rifabutin

247
Q

A patient with tuberculosis is on a medication that blocks the 30S subunit of the bacterial ribosome. Identify the drug.

A

Streptomycin; this is typically a 2nd-line agent

248
Q

Which adverse effects are associated with aminoglycosides?

A

Nephrotoxicity, Neuromuscular blockade, Ototoxicity, Teratogenicity; “mean” (aminoglycoside) GNATS caNNOT kill anaerobes

249
Q

What is the mechanism of action of tigecycline?

A

Like all glycylcyclines, it binds the 30S ribosome to inhibit bacterial protein synthesis; it is bacteriostatic

250
Q

Which generation of cephalosporins work particularly well for meningitis, and why?

A

Third generation because they can cross the blood-brain barrier

251
Q

What infectious processes are commonly treated using clindamycin?

A

Aspiration pneumonia, lung abscesses, and oral infections involving anaerobic organisms

252
Q

A 65-year-old man says that ciprofloxacin worked well for previous bouts of traveler’s diarrhea. Why should another class be used this time?

A

Fluoroquinolones may cause tendinitis/tendon rupture in people older than 60 years of age (Fluoroquinolones hurt attachments to your bones)

253
Q

Aztreonam is an example of what subclass of β-lactam drugs?

A

Monobactams

254
Q

Name 3 classes of antibiotics that work by binding to the bacterial 30S ribosomal subunit.

A

Aminoglycosides (eg, gentamicin), glycylcycline (eg, tigecycline), and tetracyclines (eg, doxycycline)

255
Q

Which 2 systemic reactions accompanied by diffuse rash can be seen with vancomycin toxicity?

A

Red man syndrome (diffuse flushing) and DRESS (drug reaction with eosinophilia and systemic symptoms) syndrome

256
Q

Ceftaroline, a fifth-generation cephalosporin, is active against which organisms?

A

Gram ⊕ and gram ⊖, including MRSA (note that it has no coverage against Pseudomonas infections)

257
Q

What are the adverse effects of chloroquine?

A

Retinopathy and pruritus (particularly in dark-skinned patients)

258
Q

What are the major adverse effects associated with isoniazid?

A

Neurotoxicity and hepatotoxicity (INH: Injures Neurons and Hepatocytes), can also lower the seizure threshold

259
Q

Your patient being treated for tuberculosis experiences paresthesias in her arms and legs. How could you have prevented this adverse effect?

A

By coadministering pyridoxine (vitamin B6) to prevent neurotoxicity induced by isoniazid

260
Q

A 20-year-old woman presents with dysuria and frequency. Urinalysis is positive for nitrites and leukocyte esterase. Most common treatment?

A

Trimethoprim-sulfamethoxazole (TMP-SMX) for simple urinary tract infections

261
Q

Which of the guanosine-analog antiviral drugs is more toxic to host enzymes?

A

Ganciclovir (compared to acyclovir)

262
Q

Name 3 echinocandins.

A

Anidulafungin, caspofungin, and micafungin

263
Q

Which macrolide antibiotics inhibit cytochrome P450 enzymes?

A

Erythromycin, clarithromycin

264
Q

Which azole antifungal is best for treating Aspergillus and Candida infections?

A

Voriconazole

265
Q

Vancomycin is bactericidal, with what exception?

A

Clostridium difficile (it is bacteriostatic against it)

266
Q

A 40-year-old man with MRSA cellulitis is treated for a week with an antibiotic and notices reduced hearing in both ears. What drug was he given?

A

Vancomycin, which is associated with ototoxicity

267
Q

What is the consequence of treating latent tuberculosis solely with rifampin?

A

Development of Rapid resistance when Rifampin is used alone

268
Q

Compared to other commonly used antiviral agents, what is the half-life of cidofovir?

A

It has a long half-life

269
Q

Describe the mechanism of action of trimethoprim.

A

It blocks dihydrofolate reductase (like pyrimethamine), thus preventing bacterial replication (bacteriostatic)

270
Q

List 2 infection control agents that are not sporicidal and work by denaturing proteins and disrupting cell membranes.

A

Alcohols and chlorhexidine

271
Q

What is the mechanism of action of pyrazinamide?

A

Unknown, but it works best at acidic pH (allowing it to work in host phagolysosomes) and is converted to its active form, pyrazinoic acid

272
Q

A pregnant woman is ⊕ for a group B streptococcal infection. What antibiotic should she receive to prevent complications in the newborn?

A

Intrapartum penicillin G or ampicillin

273
Q

A young woman presents for treatment of tinea corporis. What do you need to remember when considering the antifungal griseofulvin for her?

A

It is teratogenic and contraindicated in pregnancy; perform a pregnancy test before starting therapy

274
Q

A patient has a deep tissue vanco-resistant enterococci infection. What antibiotic do you prescribe?

A

Tigecycline

275
Q

Why is chloroquine a poor treatment for Plasmodium falciparum malaria?

A

Because the resistance rate is too high

276
Q

What is the mechanism of action of abacavir?

A

A nucleoside reverse transcriptase inhibitor (NRTI); abacavir inhibits nucleotide binding to reverse transcriptase; NRTIs lack a 3′ OH group; this stops DNA synthesis

277
Q

Pancytopenia develops in a patient being treated for HIV. Which drugs should be considered to counteract this adverse effect?

A

Granulocyte colony-stimulating factor (G-CSF) and erythropoietin (EPO) to combat bone marrow suppression

278
Q

What is the mechanism of action of quaternary amines?

A

Impairment of cell membrane permeability; the effect is not sporicidal

279
Q

What is the mechanism of action of isoniazid?

A

Isoniazid targets mycolic acid synthesis in the mycobacterial cell wall

280
Q

A 39-year-old man has an acid-fast bacillus infection. After starting therapy, he can no longer see red-green colors. What is the mechanism of action of the offending agent?

A

Inhibition of arabinosyltransferase prevents carbohydrate polymerization within Mycobacterium tuberculosis cell walls; red-green color blindness indicates ethambutol toxicity

281
Q

What is the mechanism of action of polymyxin antibiotics?

A

Cause membrane damage, leakage of cell contents, and cell death by binding to the phospholipids in the membranes of gram ⊖ bacteria

282
Q

What are the adverse effects of foscarnet therapy?

A

Electrolyte abnormalities (hypo- or hypercalcemia, hypo- or hyperphosphatemia, hypomagnesemia, or hypokalemia), seizures, nephrotoxicity

283
Q

What is the mechanism by which bacteria develop resistance to chloramphenicol?

A

By acquiring a plasmid-encoded acetyltransferase that inactivates the drug

284
Q

A man with cytomegalovirus is taking a drug that causes viral DNA chain termination. What modifications must occur to activate the drug?

A

Formation of 5′-monophosphate by CMV kinase and a triphosphate by cellular kinases

285
Q

What are the major adverse effects of dapsone?

A

Hemolysis in patients with G6PD deficiency, methemoglobinemia, and agranulocytosis

286
Q

What is the mechanism of action of mebendazole?

A

Inhibition of microtubules

287
Q

A man presents with both mucocutaneous and genital herpes simplex virus lesions. Which antiviral agents may be considered?

A

Acyclovir, valacyclovir, famciclovir

288
Q

A patient is started on a drug for influenza with the goal of shortening the duration of symptoms. What is the mechanism of action of the drug?

A

Inhibition of viral neuraminidase, which blocks the release of viral progeny (the drug is oseltamivir or zanamivir)

289
Q

A strain of tuberculosis is resistant to treatment with isoniazid. What is the mechanism of resistance?

A

Mutations that lead to the underexpression of KatG

290
Q

A 70-year-old man on warfarin is started on a sulfonamide for an infection. He soon notes easy bruising and dark tarry stools. What happened?

A

Sulfonamides increase plasma concentration of warfarin (and other drugs) by displacing it from albumin

291
Q

A patient being treated for HIV experiences paresthesia and ↓ sensation in both legs. What is the most likely cause?

A

Nucleoside reverse transcriptase inhibitor- (NRTI) induced peripheral neuropathy

292
Q

A patient being treated with clindamycin for pneumonia develops fever and loose stools. What is the bacterial culprit?

A

Clostridium difficile overgrowth in the colon

293
Q

A patient has a Pediculus and Pthirus infection. Which anti-mite/louse agents can be used?

A

Treat PML (Pesty Mites and Lice) with PML (Permethrin, Malathion, Lindane) because they NAG you (Na, AChE, GABA blockade)

294
Q

What is the recommended combination of antiretroviral therapy (ART) classes in HIV therapy?

A

2 nucleoside reverse transcriptase inhibitors (NRTIs) and a third agent (integrase inhibitors are preferred)

295
Q

Why are fluoroquinolones contraindicated in women who are pregnant or nursing and patients younger than 18 years of age?

A

Possibility of cartilage damage (fluoroquinolones hurt attachments to your bones)

296
Q

A patient requests prophylaxis against Mycobacterium tuberculosis before travel. What is the one drug that can be used as solo prophylaxis?

A

Isoniazid

297
Q

What is the mechanism of action of ribavirin?

A

Competitive inhibition of inosine monophosphate dehydrogenase, thereby inhibiting synthesis of guanine nucleotides

298
Q

Which drug is flucytosine frequently paired with to treat systemic fungal infections?

A

Amphotericin B (especially in cases of cryptococcal meningitis)

299
Q

How many generations of cephalosporins antibiotics are there?

A

5 generations

300
Q

What is the mechanism of hydrogen peroxide in disinfection and sterilization?

A

Induction of free radical oxidation; the effect is sporocidal

301
Q

What is the mechanism of action of elvitegravir?

A

As an integrase inhibitor, elvitegravir stops HIV genome integration into host cell DNA

302
Q

What antibiotic is used as prophylaxis against postsurgical Staphylococcus aureus infection?

A

Cefazolin

303
Q

A certain antibiotic inhibits bacterial translocation and the ribosomal activity is measured. Would 30S activity be decreased?

A

No, antibiotics that act on translocation all inhibit the 50S subunit (eg, macrolides, clindamycin)

304
Q

What organisms are targeted by clindamycin?

A

Organisms causing anaerobic lung infections (eg, Clostridium perfringens, Bacteroides spp) and organisms causing group A streptococcal infections

305
Q

Which protein synthesis-inhibiting antibiotics are bactericidal?

A

Aminoglycosides (note that linezolid is variable: bacteriostatic and bactericidal)

306
Q

A patient taking an oxazolidinone for MRSA complains of headache and rapid heart rate. On exam he is shivering. Other adverse effects of this drug?

A

Peripheral neuropathy, bone marrow suppression (especially thrombocytopenia) from linezolid toxicity, serotonin syndrome

307
Q

A patient being treated for tuberculosis presents with fatigue and a low hemoglobin level. The blood smear shows ringed sideroblasts. What is the most likely cause?

A

Isoniazid-induced pyridoxine (vitamin B6) deficiency; diagnosis: sideroblastic anemia

308
Q

A patient with HIV is found to have a CD4+ count <50 cells/mm3. Aside from trimethoprim-sulfamethoxazole (TMP-SMX), what other prophylactic therapy should be started?

A

Azithromycin or clarithromycin for Mycobacterium avium complex

309
Q

Fungi treated with a certain antifungal agent have ↑ amounts of intracellular lanosterol. Which cellular structure is likely compromised?

A

The cell membrane (due to azoles inhibiting intracellular 14-α-demethylase, which reduces ergosterol synthesis)

310
Q

Name the antibiotic that belongs to the oxazolidinone class.

A

Linezolid

311
Q

Trimethoprim-sulfamethoxazole is used to treat which pulmonary infection in patients who are HIV ⊕?

A

Pneumocystis jirovecii pneumonia

312
Q

A woman has a herpes simplex virus infection that does not respond to acyclovir. What drug should you try next?

A

Cidofovir or foscarnet, viral DNA polymerase inhibitors that are useful for acyclovir-resistant HSV

313
Q

A patient with HIV has a CD4+ count of 150 cells/mm3. Prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMX) is started. What infection is the patient being protected against?

A

Pneumocystis pneumonia (if CD4+ count is <200 cells/mm3)

314
Q

What is the mechanism of action of tetracyclines?

A

They are bacteriostatic, binding to 30S and preventing the attachment of aminoacyl-tRNA

315
Q

What are the most common uses for chloramphenicol?

A

Treatment of meningitis (Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae) and rickettsial diseases (eg, Rocky Mountain spotted fever)

316
Q

What is the mechanism of action of praziquantel?

A

↑ Ca2+ permeability and vacuolization

317
Q

Which organisms do second-generation cephalosporins cover?

A

Gram ⊕ cocci, Haemophilus influenzae, Enterobacter aerogenes, Neisseria spp, Serratia marcescens, Proteus mirabilis, Escherichia coli, Klebsiella (HENS PEcK)

318
Q

A woman has recurrent dysuria, urgency, and frequency. What do you prescribe as prophylaxis against future infections?

A

Trimethoprim-sulfamethoxazole (TMP-SMX) is given for recurrent UTIs

319
Q

Name 4 drugs that can be given with penicillin antibiotics to prevent degradation of the antibiotics by β-lactamase (penicillinase).

A

β-lactamase inhibitors: Clavulanic acid, Avibactam, Sulbactam, Tazobactam (CAST)

320
Q

Tetracyclines are used to treat infections with which 2 organisms that are transmitted by ticks?

A

Borrelia burgdorferi and Rickettsia

321
Q

What is a common suffix for drugs of the protease inhibitor class used to treat HIV?

A

-navir: atazanavir, darunavir, fosamprenavir, indinavir, lopinavir, ritonavir, saquinavir

322
Q

Which antibiotic is most commonly used preoperatively to protect against Staphylococcus aureus wound infections?

A

Cefazolin

323
Q

Name the drugs that belong to the sulfonamide class.

A

Sulfamethoxazole (SMX), sulfadiazine, sulfisoxazole

324
Q

Name the narrow spectrum, penicillinase resistant antibiotics.

A

Dicloxacillin, nafcillin, oxacillin

325
Q

Why are tetracyclines contraindicated in pregnancy?

A

Because they inhibit bone growth in children

326
Q

What is the mechanism of action of metronidazole?

A

Forms free radical metabolites that damage bacterial DNA, leading to cell death (bactericidal)

327
Q

Which organisms are typically not covered by the first 4 generations of cephalosporins?

A

LAME: Listeria, Atypicals (Chlamydia, Mycoplasma), MRSA, Enterococci

328
Q

What is the mechanism of resistance of Plasmodium falciparum to chloroquine?

A

Membrane pumps ↓ intracellular concentrations of the drug

329
Q

Why do antibiotics that inhibit protein synthesis generally not affect human cells?

A

They target bacterial ribosome 70S, which is smaller than the 80S of humans; thus human ribosomes are left unaffected

330
Q

What drug is used for Mycobacterium tuberculosis prophylaxis?

A

Isoniazid

331
Q

A patient being treated for HIV exhibits a rash and ↑ values on liver function tests. What is the most likely cause?

A

A non-nucleoside reverse transcriptase inhibitor (NNRTI); a rash and hepatotoxicity are common adverse effects of all NNRTIs

332
Q

Anion gap metabolic acidosis develops in a patient being treated for HIV. What is the most likely cause?

A

Nucleoside reverse transcriptase inhibitor- (NRTI) induced lactic acidosis (nucleoside agents only)

333
Q

What drug regimen can you use to treat a Mycobacterium avium-intracellulare infection?

A

Azithromycin or clarithromycin plus ethambutol; rifabutin or ciprofloxacin can be added

334
Q

Name the penicillins that are effective against Pseudomonas spp.

A

Piperacillin and ticarcillin

335
Q

Why should ribavirin be used with caution in young women?

A

It is teratogenic

336
Q

You add amphotericin B to a fungal culture and note an ↑ in the electrolyte content of the culture media. Explain the mechanism.

A

Amphotericin B binds ergosterol (unique to fungi) and forms membrane pores (“tears” holes), allowing leakage of electrolytes

337
Q

A man receives acyclovir for a viral infection that is later found to be cytomegalovirus. How does the management change?

A

Acyclovir is not effective against CMV, so ganciclovir or a viral DNA polymerase inhibitor (eg, foscarnet, cidofovir) should be used instead

338
Q

A patient who is HIV ⊕ contracts tuberculosis. Why is rifabutin favored over rifampin in this case?

A

Less P-450 stimulation (Rifampin ramps up cytochrome P-450, but rifabutin does not)

339
Q

What is the mechanism of action of acyclovir?

A

It is a guanosine analog that inhibits DNA replication

340
Q

An antifungal agent interferes with mitotic spindles. Which conditions is this drug used for?

A

Superficial infections (oral therapy) and dermatophytoses; the drug is griseofulvin

341
Q

An immunocompromised man has cytomegalovirus retinitis that does not respond to ganciclovir. Which antiviral agent should be considered?

A

Foscarnet

342
Q

Which of the 2 aminopenicillins has a greater oral bioavailability?

A

Amoxicillin (AmOxicillin has better Oral bioavailability)

343
Q

What is the mechanism of action of the antipseudomonal penicillins?

A

Same as that of penicillin (they inhibit peptidoglycan cross-linking in bacterial cell walls)

344
Q

Name 2 viral DNA polymerase inhibitors and the 2 viruses they are commonly used to treat.

A

Cidofovir and foscarnet (for herpes simplex virus and cytomegalovirus)

345
Q

A patient treated for onychomycosis complains of gastrointestinal upset, headache, and taste disturbance; liver function test results are abnormal. Most likely cause?

A

Terbinafine toxicity

346
Q

A patient being treated for tuberculosis experiences tinnitus, vertigo, ataxia, and nephrotoxicity. Which antimycobacterial agent is the most likely cause?

A

Streptomycin

347
Q

A patient with COPD being treated with inhaled steroids has oral candidiasis (thrush). What medication do you prescribe?

A

Nystatin (swish and swallow)

348
Q

What is the major toxicity associated with ethambutol?

A

Potentially reversible optic neuropathy, commonly manifesting as red-green color blindness; think “eyethambutol”

349
Q

Which protein synthesis-inhibiting antibiotics are bacteriostatic?

A

Tetracyclines, chloramphenicol, clindamycin, erythromycin (linezolid is variable: bacteriostatic and bactericidal)

350
Q

A patient is on voriconazole for a serious Aspergillus infection, but the infection worsened. What azole should be used next?

A

Isavuconazole

351
Q

Which antibiotics can be used to treat vancomycin-resistant enterococci (VRE)?

A

Linezolid, streptogramins (quinupristin, dalfopristin), and tigecycline

352
Q

What is the mechanism of action of dicloxacillin, nafcillin, and oxacillin?

A

Inhibit peptidoglycan cross-linking in bacteria cell walls (same as penicillin)

353
Q

What is the treatment for tuberculoid leprosy?

A

Long-term regimen of dapsone and rifampin

354
Q

A man with HIV finds that taking his HIV protease inhibitor makes some other medications more potent. Inhibition of which enzyme is to blame?

A

Cytochrome P-450, which is inhibited by ritonavir

355
Q

Fourth-generation cephalosporins have ↑ activity against which organisms?

A

Pseudomonas and gram ⊕ organisms

356
Q

Name the fourth-generation cephalosporin.

A

Cefepime

357
Q

Carbapenems are used to treat infections with which type of organisms?

A

Gram ⊕ cocci, gram ⊖ rods, and anaerobes (wide spectrum)

358
Q

What are the adverse effects of therapy with amphotericin B?

A

Think “amphoterrible” B: fevers/chills (“shake and bake”), nephrotoxicity, hypotension, anemia, arrhythmias, IV phlebitis

359
Q

Which agent, when given with amoxicillin, protects against β-lactamases?

A

Clavulanic acid

360
Q

What drug prevents HIV virions from attaching to host cells?

A

Maraviroc

361
Q

An HIV drug inhibits reverse transcriptase. What 2 classes of HIV drugs utilize this mechanism of action?

A

Nucleoside reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs)

362
Q

Name the penicillins that are sensitive to penicillinase.

A

Penicillin and the aminopenicillin family (amoxicillin and ampicillin)

363
Q

Name 2 antipseudomonal antibiotics that interfere with peptidoglycan cross-linking.

A

Ticarcillin, piperacillin

364
Q

What are the current guidelines for initiation of antiretroviral therapy (ART)?

A

ART is commonly started at diagnosis of HIV; high viral load or presence of AIDS-defining illness is a stronger indication for starting treatment

365
Q

What is the 4-drug therapy commonly used to treat tuberculosis?

A

Rifampin, Isoniazid, Pyrazinamide, and Ethambutol (RIPE for treatment)

366
Q

A patient with HIV is on a medication that binds to gp41 protein. Which class of HIV medication does this drug belong to?

A

Fusion inhibitors, which prevent viral entry; this is enfuvirtide

367
Q

What organisms does tigecycline cover?

A

Broad-spectrum anaerobic gram ⊖ and gram ⊕ organisms, multidrug-resistant organisms (MRSA, VRE); also deep tissue infections

368
Q

Renal failure is found in a patient being treated for cytomegalovirus retinitis who presented with multiple seizures. What is the most likely cause of the renal failure?

A

Foscarnet-induced nephrotoxicity (foscarnet can also induce seizures)

369
Q

What is the mechanism of action of ledipasvir and ombitasvir?

A

NS5A inhibition, preventing RNA replication

370
Q

What is the function of the HIV-1 protease from the pol gene?

A

Cleaving the polypeptides made from the HIV mRNA into functional components

371
Q

What is the antiprotozoal agent of choice for a Trypanosoma cruzi infection?

A

Nifurtimox

372
Q

A patient being treated for HIV has upper abdominal pain radiating to the back and Grey Turner sign. What’s the most likely cause?

A

Didanosine-induced pancreatitis

373
Q

A patient with HIV has a CD4+ count <100 cells/mm3. Prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMX) is started. What infection is the patient being protected against?

A

Pneumocystis pneumonia (if CD4+ count is <200 cells/mm3) and toxoplasmosis (if CD4+ count is <100 cells/mm3)

374
Q

What is the mechanism by which mycobacteria develop resistance to rifamycin, particularly with monotherapy?

A

Mutations ↓ the drug’s ability to bind to the RNA polymerase

375
Q

How do fluoroquinolones and quinolones exert their antibacterial effects?

A

DNA gyrase inhibition

376
Q

Name 2 examples of first-generation cephalosporins.

A

Cefazolin and cephalexin

377
Q

Name some specific bugs that penicillin is particularly effective against.

A

Streptococcus pneumoniae, Streptococcus pyogenes, Actinomyces, Neisseria meningitidis, Treponema pallidum

378
Q

Which disinfection and sterilization techniques are not sporicidal?

A

Alcohols, chlorhexadine, quaternary amines

379
Q

Compared to that of other β-lactams, cephalosporins are more resistant to what enzyme?

A

Penicillinase

380
Q

Why should griseofulvin be used with caution in young women?

A

It is teratogenic

381
Q

Penicillin is the prototype for which class of antibiotics?

A

β-lactams

382
Q

What is the mechanism of action of chlorine against spores?

A

Oxidation and denaturation of proteins; the effect is sporicidal

383
Q

A patient with methicillin-resistant Staphylococcus aureus is given an antibiotic that has decreased absorption when taken with milk. Which antibiotic class does this drug belong to?

A

Tetracyclines; this is doxycycline

384
Q

Name 5 uses for tetracyclines.

A

Treat Mycoplasma pneumoniae, Chlamydia, Borrelia burgdorferi, and Rickettsia infections, and acne

385
Q

A patient with an inherited mutation causing ↑ dehydropeptidase I activity is given meropenem to treat septicemia. How does this affect seizure risk?

A

Meropenem is resistant to dehydropeptidase I activity, so its plasma levels will not ↑; therefore, no change to the risk of seizures

386
Q

Aztreonam inhibits peptidoglycan cross-linking by binding to which substance?

A

Penicillin-binding protein 3

387
Q

What are the musculoskeletal adverse effects of fluoroquinolones

A

Leg cramps, myalgia, tendonitis and tendon rupture (in those over 60 years of age or who are taking prednisone), and damage to cartilage in children

388
Q

An unvaccinated child contracts Haemophilus influenzae type b. Which antimycobacterial agents may be used as prophylaxis for the child’s contacts?

A

Rifampin, rifabutin

389
Q

What is the mechanism of action of lindane?

A

Blockage of GABA channels, thereby causing neurotoxicity

390
Q

What is the antiprotozoal agent of choice for toxoplasmosis?

A

Pyrimethamine

391
Q

Which drugs can you prescribe to a patient with Plasmodium falciparum malaria?

A

Artemether/lumefantrine or atovaquone/proguanil

392
Q

What agents is autoclaving not reliably successful against?

A

Prions

393
Q

You want to prescribe a triple therapy regimen for a patient with Helicobacter pylori, but she has a penicillin allergy. How do you alter your treatment plan?

A

Replace amoxicillin with metronidazole (triple therapy also includes a proton pump inhibitor and clarithromycin)

394
Q

An infant has a diaper rash that you determine is a fungal infection. You prescribe a topical medication. What is its mechanism of action?

A

It forms membrane pores on fungi, allowing electrolytes to leak; the drug is nystatin

395
Q

Why are tetracycline antibiotics not a good choice for infections of the central nervous system (CNS)?

A

They have limited CNS penetration

396
Q

A man with a systemic cryptococcal infection develops meningitis. How must you change the regimen of amphotericin B?

A

Consider intrathecal administration and co-administering with flucytosine

397
Q

Which antibiotics belong to the carbapenem group?

A

Doripenem, ertapenem, imipenem, meropenem

398
Q

Name 4 examples of third-generation cephalosporins.

A

Ceftriaxone, cefotaxime, ceftazidime, cefpodoxime

399
Q

What is the mechanism of action of flucytosine?

A

Flucytosine is converted to 5-fluorouracil by cytosine deaminase; 5-fluorouracil inhibits DNA and RNA synthesis

400
Q

What medications can be given to travelers for malaria prophylaxis?

A

Atovaquone-proguanil, mefloquine, doxycycline, primaquine, or chloroquine (for areas with sensitive species)

401
Q

A patient with strep throat is allergic to penicillin. Which part of protein synthesis is inhibited by the antibiotic that he receives instead?

A

Translocation; he was likely given a macrolide antibiotic; think macroslides

402
Q

A patient takes trimethoprim-sulfamethoxazole (TMP-SMX) and you later observe megaloblasts on a blood smear. How could this have been prevented?

A

By coadministration of leucovorin (folinic acid); TMP-SMX can cause megaloblastic anemia, leukopenia, granulocytopenia, and hyperkalemia (TMP Treats Marrow Poorly)

403
Q

Sulfonamides are active against which organisms?

A

Gram ⊕ and gram ⊖ organisms, Nocardia

404
Q

Trimethoprim and sulfamethoxazole are used in combination to treat which types of infections?

A

Urinary tract infections, toxoplasmosis prophylaxis, Shigella, Salmonella, and Pneumocystis jirovecii pneumonia treatment and prophylaxis

405
Q

Adding a guanine nucleotide synthesis blocker to virus-infected cells blocks virion assembly. What 2 viruses may be infecting these cells?

A

Respiratory syncytial virus or hepatitis C virus (the drug is likely ribavirin)

406
Q

How does griseofulvin influence cancer risk?

A

It is carcinogenic, so cancer risk is ↑

407
Q

What are the adverse effects of the NS3/4A inhibitors grazoprevir and simeprevir?

A

Grazoprevir causes photosensitivity and rash; simeprevir causes headache and fatigue

408
Q

How do viruses develop resistance to ganciclovir?

A

By a mutated viral kinase

409
Q

Name 2 antibiotics that work by blocking peptidoglycan synthesis.

A

Bacitracin and vancomycin (glycopeptides)

410
Q

How do iodine and iodophors work to control infection?

A

Halogenation of proteins, RNA, and DNA; may be sporicidal

411
Q

Monobactams are particularly useful in which patient populations infected with gram ⊖ rods?

A

In patients with penicillin allergy or patients with renal insufficiency in whom aminoglycosides should be avoided

412
Q

Against which classes of bacteria do penicillins exhibit bactericidal activity?

A

Gram ⊕ cocci, gram ⊖ cocci, gram ⊕ rods, spirochetes

413
Q

What are the adverse effects of the NS5B inhibitors sofosbuvir and dasabuvir?

A

Fatigue, headache

414
Q

A patient who recently started an antibiotic for tuberculosis has orange-colored urine and sweat. What is the drug’s mechanism of action?

A

Inhibition of DNA-dependent RNA polymerase; this is Rifamycin, RNA polymerase inhibitor

415
Q

List the organisms that can be treated with metronidazole.

A

Giardia, Entamoeba, Trichomonas, Gardnerella vaginalis, Anaerobes (Bacteroides, Clostridium difficile), Helicobacter pylori (GET GAP on the Metro with metronidazole!)

416
Q

What prophylaxis do you give for streptococcal pharyngitis in a boy with a history of rheumatic fever?

A

Oral penicillin V or benzathine penicillin G

417
Q

β-lactamase inhibitors are used to protect antibiotics from bacterial penicillinases. Would you use these with vancomycin?

A

No, because vancomycin is resistant to β-lactamases

418
Q

Ethambutol is used to treat which bacterial infection?

A

Mycobacterium tuberculosis

419
Q

Against which organisms are dicloxacillin, nafcillin, and oxacillin useful?

A

Staphylococcus aureus (use naf [nafcillin] for staph)

420
Q

Name 3 non-nucleoside reverse transcriptase inhibitors (NNRTIs) used to treat HIV.

A

Delavirdine, efavirenz, nevirapine

421
Q

A patient currently on erythromycin is found to have an electrical cardiac abnormality on EKG. What is it most likely to be?

A

Prolonged QT interval

422
Q

A drug added to HIV-infected cells stops viral particle budding and release. HIV proteins remain w/in cells. Which drug class was added?

A

A protease inhibitor (eg, atazanavir), which blocks proteolytic processing

423
Q

Name 3 examples of macrolide antibiotics.

A

Erythromycin, azithromycin, and clarithromycin

424
Q

Apart from tuberculosis, which other mycobacterial infection is rifampin used for?

A

Mycobacterium leprae (it delays resistance to dapsone)

425
Q

What are the 5 adverse effects caused by macrolides?

A

MACRO: GI Motility issues, Arrhythmia (prolonged QT), acute Cholestatic hepatitis, Rash, eOsinophilia

426
Q

What are some of the conditions for which daptomycin is used?

A

Vancomycin-resistant enterococcus, bacteremia, endocarditis, and skin infections with Staphylococcus aureus (especially MRSA)

427
Q

What antibiotics could you prescribe for a patient who is HIV+ with a CD4+ count of 10 to protect against Mycobacterium avium-intracellulare infection?

A

Azithromycin or rifabutin

428
Q

What disease is dapsone used to treat, and what disease is it used for prophylaxis?

A

Treatment: leprosy (for both lepromatous and tuberculoid forms); prophylaxis: Pneumocystis jirovecii (treatment if used with trimethoprim)

429
Q

What alkylating agent can be used for sterilization?

A

Ethylene oxide

NBME Micro (36 decks)

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