ABIM Infectious Disease flashcards

37 cards. Read the term and the definition here. The deck at the top of this page is optional.

MRSA resistance mechanism

Methicillin resistance is mediated by the mecA gene, which encodes PBP2a, a penicillin-binding protein with low affinity for beta-lactams, conferring resistance to all beta-lactams except ceftaroline.

Vancomycin AUC target

For serious MRSA infections, the recommended pharmacodynamic target is an AUC/MIC ratio of 400 to 600, which is associated with improved outcomes and reduced nephrotoxicity versus trough-only monitoring.

Endocarditis empiric therapy

For native valve endocarditis, empiric therapy is vancomycin plus ceftriaxone; for prosthetic valve endocarditis, add gentamicin and rifampin for staphylococcal coverage.

C. difficile first-line therapy

Oral vancomycin or fidaxomicin is first-line for initial and recurrent Clostridioides difficile infection; metronidazole is reserved for when these agents are unavailable.

Necrotizing fasciitis management

Immediate surgical debridement is the primary intervention; broad-spectrum antibiotics are adjunctive and cannot substitute for source control, which determines outcome.

Acyclovir activation mechanism

Acyclovir is phosphorylated by viral thymidine kinase to a monophosphate, then by cellular kinases to a triphosphate that inhibits viral DNA polymerase; thymidine kinase mutations cause resistance.

CMV ganciclovir resistance

Ganciclovir requires phosphorylation by UL97 kinase; UL97 mutations cause ganciclovir resistance, while UL54 DNA polymerase mutations may confer cross-resistance to cidofovir and foscarnet.

Hepatitis C SVR12

SVR12 is undetectable hepatitis C RNA 12 weeks after completing direct-acting antiviral therapy; it is the accepted endpoint for cure and exceeds 95% across genotypes.

Measles post-exposure prophylaxis

For susceptible contacts, MMR vaccine is given within 72 hours of exposure; immunoglobulin is given within 6 days for those who cannot receive live vaccine, such as immunocompromised or pregnant patients.

Amphotericin B mechanism

Amphotericin B binds ergosterol in the fungal membrane, forming pores that cause leakage and cell death; liposomal formulations reduce nephrotoxicity and infusion reactions.

Echinocandin mechanism

Echinocandins inhibit beta-1,3-D-glucan synthase, disrupting fungal cell wall synthesis; they are fungicidal against Candida and fungistatic against Aspergillus.

Cryptococcal meningitis induction

Induction therapy for cryptococcal meningitis is amphotericin B plus flucytosine for at least 2 weeks, followed by fluconazole consolidation; elevated intracranial pressure requires serial therapeutic lumbar drainage.

Mucormycosis treatment

Mucormycosis is treated with high-dose liposomal amphotericin B plus urgent surgical debridement; voriconazole is inactive against Mucorales and should not be used.

Pneumocystis first-line therapy

Trimethoprim-sulfamethoxazole is first-line for Pneumocystis jirovecii pneumonia and for prophylaxis; alternatives include atovaquone, pentamidine, and clindamycin-primaquine.

Latent TB regimens

Standard latent TB regimens are 4 months of rifampin, 3 months of weekly isoniazid plus rifapentine, or 9 months of isoniazid; active disease must be excluded before treatment.

Drug-susceptible TB regimen

Drug-susceptible pulmonary TB is treated with 2 months of isoniazid, rifampin, pyrazinamide, and ethambutol, followed by 4 months of isoniazid plus rifampin.

Isoniazid toxicity

Isoniazid causes hepatotoxicity and peripheral neuropathy, which is prevented with pyridoxine; rifampin induces CYP450 enzymes and turns body fluids orange.

Ethambutol optic neuritis

Ethambutol causes dose-related optic neuritis with loss of red-green discrimination; baseline and periodic visual acuity and color vision testing are recommended, especially at higher doses.

Severe malaria treatment

Severe falciparum malaria is treated with intravenous artesunate; uncomplicated disease uses artemisinin-based combination therapy, and vivax or ovale infection requires primaquine after G6PD testing.

Babesiosis treatment

Mild babesiosis is treated with azithromycin plus atovaquone; severe disease uses clindamycin plus quinine; consider babesiosis in asplenic or post-transplant patients with fever and hemolysis.

Strongyloides hyperinfection

Strongyloides hyperinfection occurs with corticosteroid use or HTLV-1 infection and requires ivermectin; disseminated disease carries high mortality and needs prolonged therapy.

Toxoplasmosis treatment

Toxoplasmosis is treated with pyrimethamine plus sulfadiazine plus folinic acid; in pregnancy, spiramycin is used to reduce fetal transmission.

Hand hygiene priority

Hand hygiene is the single most effective measure to prevent healthcare-associated infection; alcohol-based rub is preferred except for C. difficile, for which soap and water is used.

CLABSI prevention bundle

The central line bundle includes hand hygiene, maximal barrier precautions, chlorhexidine skin antisepsis, optimal site selection, and daily review of line necessity.

Asymptomatic bacteriuria rule

Asymptomatic bacteriuria should not be treated except in pregnancy or before urologic procedures; treating it otherwise promotes resistance and does not improve outcomes.

Stewardship core strategies

Antimicrobial stewardship core strategies include preauthorization, prospective audit with feedback, de-escalation, dose optimization, and duration limits.

Neutropenic fever empiric therapy

Neutropenic fever requires prompt empiric anti-pseudomonal beta-lactam therapy; vancomycin is added for suspected line infection, mucositis, or hemodynamic instability.

Post-transplant infection timeline

The first month carries bacterial and candidal infections; months 1 to 6 carry opportunistic infections such as CMV, Pneumocystis, and Aspergillus; after 6 months, community-acquired infections predominate.

Asplenia infection risk

Asplenic patients are at risk for encapsulated organisms, especially Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis; vaccination and prophylaxis are indicated.

HIV PEP timing

HIV post-exposure prophylaxis should start within 72 hours of exposure and continue for 28 days with a three-drug regimen, with baseline and follow-up HIV testing.

Syphilis in pregnancy

Benzathine penicillin G is the only recommended treatment for syphilis in pregnancy; penicillin-allergic pregnant patients require desensitization rather than alternative antibiotics.

Gonorrhea first-line therapy

Ceftriaxone 500 mg intramuscularly is first-line for gonorrhea; test for cure in pharyngeal infection and in pregnancy, and screen for chlamydia coinfection.

Yellow fever vaccine contraindication

Yellow fever vaccine is live and contraindicated in severe immunocompromise and pregnancy unless exposure risk is high; a single dose confers long-term protection.

Rabies post-exposure prophylaxis

Rabies post-exposure prophylaxis involves wound washing, a vaccine series, and rabies immunoglobulin infiltrated at the wound for category III exposures and immunocompromised patients.

Blood culture collection

Obtain at least two sets of blood cultures from separate sites before antibiotics; each set includes aerobic and anaerobic bottles; avoid drawing through existing lines unless line infection is suspected.

C. difficile testing algorithm

A two-step algorithm using GDH or NAAT followed by toxin enzyme immunoassay improves positive predictive value; testing formed stool is not appropriate.

MIC definition

The minimum inhibitory concentration is the lowest antimicrobial concentration that inhibits visible growth of the organism; it is interpreted using CLSI or EUCAST breakpoints.