Study guide
Infectious Diseases: High-Yield PANCE Review
Infectious Diseases comprises roughly 6% of the NCCPA PANCE blueprint (effective Jan 2025) and is also woven through every organ system, making pathogen identification, empiric therapy, and prophylaxis among the most consistently tested content on the exam.
Sepsis, Bacteremia & Empiric Antibiotic Principles
- ◆Sepsis = life-threatening organ dysfunction from dysregulated host response to infection; qSOFA (RR ≥22, SBP ≤100, altered mentation — ≥2 = high risk) is a bedside prompt, but Surviving Sepsis 2021 advises against qSOFA as a SOLE screening tool versus SIRS/NEWS/MEWS.
- ◆Hour-1 bundle: obtain lactate and blood cultures BEFORE antibiotics, give broad-spectrum antibiotics, and start 30 mL/kg crystalloid for hypotension or lactate ≥4; norepinephrine is the first-line vasopressor.
- ◆Empiric coverage targets likely source: add vancomycin for MRSA risk and an antipseudomonal beta-lactam (piperacillin-tazobactam, cefepime, or meropenem) for hospital-acquired/neutropenic cases.
- ◆Neutropenic fever (ANC <500 + temp ≥38.3°C, or ≥38.0°C sustained) is an emergency — start monotherapy with cefepime or piperacillin-tazobactam immediately; do not wait for a source.
- ◆C. difficile colitis first-line is now oral fidaxomicin (preferred) or oral vancomycin per the 2021 IDSA-SHEA update (NOT metronidazole, reserved for mild disease when neither is available); stop the offending antibiotic and avoid antimotility agents.
Meningitis & CNS Infections
- ◆Classic triad: fever, nuchal rigidity, altered mental status; check Kernig/Brudzinski. Do LP unless focal deficit, papilledema, or immunocompromise — then CT head first, but never delay antibiotics.
- ◆Bacterial CSF: high opening pressure, high protein, LOW glucose, PMN predominance, thousands of WBCs. Viral: normal glucose, lymphocytes, mildly elevated protein.
- ◆Empiric therapy: ceftriaxone + vancomycin for all adults; ADD ampicillin if age >50, pregnant, or immunocompromised to cover Listeria.
- ◆Give dexamethasone before or with the first antibiotic dose in suspected pneumococcal meningitis (reduces neurologic sequelae).
- ◆Meningococcal (N. meningitidis) exposure → rifampin, ciprofloxacin, or ceftriaxone prophylaxis for close contacts. HSV encephalitis (temporal lobe) → IV acyclovir empirically.
Tick-Borne & Spirochetal Diseases
- ◆Lyme (Borrelia burgdorferi): early localized = erythema migrans (target/bull's-eye) → doxycycline 100 mg PO BID x10 days, now first-line for ALL ages including young children per the 2020 IDSA/AAN/ACR guideline (short courses do not stain teeth); amoxicillin x14d or cefuroxime are alternatives, and doxycycline is still avoided in pregnancy. Two-tier ELISA then Western blot (or a second EIA) for later disease.
- ◆Lyme carditis (high-grade AV block) or neuroborreliosis → IV ceftriaxone. Bell palsy can be a Lyme manifestation in endemic areas.
- ◆Rocky Mountain spotted fever (Rickettsia rickettsii): fever + headache + rash starting on WRISTS/ANKLES spreading centrally and involving PALMS/SOLES → doxycycline first-line for ALL ages including children; do not wait for serology.
- ◆Ehrlichiosis/Anaplasmosis: fever + leukopenia + thrombocytopenia + elevated transaminases, typically WITHOUT rash → doxycycline.
- ◆Syphilis (Treponema pallidum): primary = painless chancre; secondary = diffuse rash including palms/soles + condyloma lata. Primary/secondary/early latent → benzathine penicillin G 2.4 million units IM x1; late latent → 3 weekly doses; neurosyphilis → IV aqueous penicillin G.
HIV/AIDS & Opportunistic Infection Prophylaxis
- ◆Diagnose with 4th-gen antigen/antibody combo immunoassay (detects p24) confirmed by an HIV-1/HIV-2 differentiation assay; start antiretroviral therapy (ART) in ALL patients regardless of CD4 count.
- ◆AIDS = CD4 <200 or an AIDS-defining illness. Track viral load for treatment response; goal is undetectable (U=U, untransmittable).
- ◆PCP (Pneumocystis jirovecii) prophylaxis with TMP-SMX when CD4 <200; add prednisone if PaO2 <70 or A-a gradient >35. Toxoplasma prophylaxis (TMP-SMX) at CD4 <100 if IgG-positive.
- ◆CD4 <50 → risk of MAC (disseminated) and CMV retinitis (perivascular hemorrhages, 'pizza-pie' fundus). Prompt ART is the mainstay; routine primary MAC prophylaxis is NO longer recommended when ART is started immediately (reserve for those not on/failing ART).
- ◆PrEP (tenofovir/emtricitabine, or injectable cabotegravir) for high-risk HIV-negative patients; PEP within 72 hours of exposure. Cryptococcal meningitis → amphotericin B + flucytosine induction, then fluconazole.
Viral Hepatitis Serologies & Management
- ◆Acute Hep B window period: HBsAg negative, anti-HBs negative, but anti-HBc IgM POSITIVE — the only marker present. Immunity from vaccine = isolated anti-HBs; immunity from prior infection = anti-HBs + anti-HBc.
- ◆Chronic Hep B = HBsAg positive >6 months; HBeAg indicates high infectivity/replication. Treat active disease with tenofovir or entecavir.
- ◆Hepatitis C: USPSTF recommends screening ALL adults aged 18–79 at least once (Grade B); diagnose with anti-HCV antibody then confirm with HCV RNA. Curable with direct-acting antivirals (e.g., sofosbuvir-based) in >95%.
- ◆Hepatitis A and E are fecal-oral and self-limited; Hep E is dangerous in pregnancy. Hep D only co-infects with Hep B.
- ◆Post-exposure to HBsAg-positive source in unvaccinated person → HBIG + hepatitis B vaccine series.
Common Viral & Board-Favorite Infections
- ◆Infectious mononucleosis (EBV): fever, posterior cervical lymphadenopathy, exudative pharyngitis, splenomegaly, +heterophile (Monospot). Avoid amoxicillin/ampicillin (causes rash) and avoid contact sports ≥3 weeks (splenic rupture risk).
- ◆Influenza: oseltamivir is most effective within 48 hours of symptom onset; annual vaccination is the key preventive measure.
- ◆Mumps (parotitis), measles (Koplik spots + cephalocaudal rash), rubella (posterior auricular nodes), and varicella are MMR/vaccine-preventable board staples — measles is highly contagious with airborne precautions.
- ◆Cellulitis (Strep) vs. purulent abscess (often MRSA): non-purulent → cephalexin; purulent → incision and drainage plus TMP-SMX or doxycycline for MRSA coverage.
- ◆Tuberculosis: RIPE (rifampin, isoniazid, pyrazinamide, ethambutol) x2 months then rifampin+isoniazid x4 months; give pyridoxine (B6) with INH to prevent neuropathy; airborne isolation and directly observed therapy.