Antibiotic selection, MRSA treatment, CAP/HAP guidelines, CDI management, UTI therapy, HIV ART, and OI prophylaxis — high-yield infectious disease content for the NAPLEX.
| Infection | Common Pathogen(s) | First-Line Treatment | Key Notes |
|---|---|---|---|
| CAP (outpatient, healthy) | S. pneumoniae, H. influenzae, atypicals | Amoxicillin or doxycycline | No comorbidities |
| CAP (outpatient, comorbidities) | Same + drug-resistant organisms | Resp FQ (levofloxacin) OR amox-clav + macrolide | DM, COPD, CKD, immunosuppression |
| MRSA (skin/SSTI) | CA-MRSA | TMP-SMX, doxycycline, or clindamycin | I&D for abscesses |
| MRSA (bacteremia) | MRSA | Vancomycin (AUC-guided) or daptomycin | Daptomycin NOT for pneumonia |
| CDI (initial, non-severe) | C. difficile | Fidaxomicin (preferred) or vancomycin PO | Metro no longer first-line |
| UTI (uncomplicated) | E. coli | Nitrofurantoin (5d) or TMP-SMX (3d) if resistance <20% | Nitrofurantoin CI if CrCl <30 |
| HIV (treatment-naive) | HIV | Biktarvy (bictegravir/TAF/FTC) preferred | INSTI-based regimen preferred |
2020 Vancomycin Guidelines: AUC/MIC-guided dosing (target AUC 400-600 mg·h/L) has replaced trough-only monitoring. Bayesian software is preferred for AUC estimation. Trough-only monitoring (15-20 mcg/mL) is no longer recommended as a primary target — it correlates poorly with efficacy and increases nephrotoxicity risk.
| OI | CD4 Threshold | Prophylaxis |
|---|---|---|
| PCP (Pneumocystis) | <200 | TMP-SMX DS daily (preferred) |
| Toxoplasma | <100 | TMP-SMX DS daily (if IgG+) |
| MAC | <50 | Azithromycin 1200mg weekly |
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