Empiric antimicrobials
Meningitis: vanc + CTX 2 g q12; add ampicillin if ≥50 or immunocompromised; acyclovir if HSV possible. Steroids if pneumococcus.
Amanda Ward5 min6 questions8 trials
The first hour
Pick a source, cover what lives there, then de-escalate. In septic , antibiotics within 1 hour of recognition beat a prettier culture later (Surviving Sepsis 2021). Blood cultures before the first dose whenever it will not delay drugs.
- 1
Name the source
Lung, urine, abdomen, skin, meninges, neutropenia, or “no source.” Hardware, travel, and recent IV antibiotics change the list.
- 2
Cover the killers
Load a β-lactam, then extend the infusion. One dose of amikacin is reasonable if MDRO Gram-negatives are likely and the patient is crashing.
- 3
Source control
Drain, debride, pull the line, ERCP, wash the joint. Antibiotics without control are a delay, not a plan.
- 4
Time-out at 48 hours
Cultures, MRSA nares, and the exam decide who still needs vancomycin and who can come off Pseudomonas.
Surviving Sepsis 2021;
By source — lung, urine, abdomen
| Source | Usual organisms | Start with | Do not miss |
|---|---|---|---|
| CAP () | Viruses > S. pneumoniae, H. influenzae, atypicals. S. aureus / Legionella when very sick. Klebsiella in alcohol use. | Healthy outpatient: amoxicillin 1 g TID (or doxy). Comorbid outpatient: amox-clav + azithro, or levo. Most inpatients: CTX + azithro (or levo). Prior MRSA/PsA or IV abx in 90 d: vanc + cefepime + azithro. | Send a viral swab. Aspiration is not metronidazole — add anaerobes only for abscess or empyema. Drain empyema. |
| HAP / VAP () | CAP organisms plus S. aureus, enteric GNR, Pseudomonas, Stenotrophomonas. ~1/5 viral. | Cefepime or ceftazidime. IV abx in the last 90 days: vancomycin + cefepime. Double-cover Pseudomonas only if resistance risk is high, then drop the second agent. | Local MDRO rates matter. Do not use daptomycin for lung. |
| UTI, non-pregnant (; ) | Uncomplicated: E. coli, Klebsiella, S. saprophyticus, Proteus. Complicated / pyelo / CAUTI: plus enterococci, Pseudomonas, Serratia, Providencia. | Cystitis: nitrofurantoin, TMP-SMX, or fosfomycin. Pyelo / complicated: CTX (FQ if susceptible). CAUTI: exchange the Foley; vanc + CTX if recent instrumentation or MRSA in urine; cefepime if Pseudomonas, carbapenem if ESBL. | Do not treat asymptomatic bacteriuria except pregnancy and mucosal urologic procedures. |
| Biliary / IAI () | E. coli, Klebsiella, enterococci, anaerobes — usually polymicrobial. Abscesses add Candida. | Low-risk: CTX + metronidazole or cipro + metronidazole. Severe / nosocomial: cefepime + metronidazole, pip-tazo, or a carbapenem. Add vanc or use pip-tazo if enterococcus is likely. | Source control is the cure (ERCP, drain, OR). Stay broad 48 h even if one bottle grows one organism. Avoid clindamycin for B. fragilis. |
| SBP () | Enteric GNR, streptococci, enterococci. Anaerobes are rare. | Ceftriaxone or cefotaxime. Cipro is for β-lactam allergy and for prophylaxis. | Start prophylaxis after the first episode. |
By source — skin, meninges, neutropenia
| Source | Usual organisms | Start with | Do not miss |
|---|---|---|---|
| SSTI () | Impetigo: S. aureus > strep. Cellulitis / erysipelas: strep > staph. Purulent: staph. Nec fasc: strep, C. perfringens, MRSA. Bites: oral flora + Pasteurella / Eikenella. | Purulent: vancomycin. Non-purulent: cefazolin. Bite: amp-sulbactam. DM / PAD ulcer: vanc + CTX or cefepime. Nec fasc: vanc + pip-tazo or meropenem ± clindamycin or linezolid (toxin suppression). | Abscesses get drained. Pain out of proportion, crepitus, or rapid spread is the OR now — imaging is not a gate. |
| Meningitis (; ) | S. pneumoniae, viruses (HSV), N. meningitidis. Age ≥50, immunocompromise, or alcohol: Listeria. Hardware / nosocomial: staph, Pseudomonas; C. acnes if a VP shunt. | Vancomycin + CTX 2 g q12h. Age ≥50: add ampicillin. HSV possible: add acyclovir. Healthcare, hardware, VP shunt, PWID: vanc + cefepime or meropenem. | Dexamethasone with the first dose if pneumococcus is likely. Remove hardware when you can (EVD for a shunt). |
| Febrile neutropenia — T ≥100.4°F and ANC <500 () | Source unidentified ~70%. When found: 60% GPC (CoNS > S. aureus, strep, enterococci), 40% GNR (E. coli, Klebsiella > Pseudomonas). | Cefepime within 1 hour. Add vancomycin for suspected CLABSI, SSTI, pneumonia, severe mucositis, hemodynamic instability, or GPCs on blood culture. Persistent fever 4–7 days: add micafungin. | Vancomycin is not automatic. If afebrile 72 h or ANC >500, de-escalate. Oral prophylaxis (levo, or amox-clav + cipro) is for prolonged neutropenia. |
Endocarditis (Circ 2015;132:1435)
- Native: S. aureus, strep, enterococci, occasional GNR, HACEK — vanc + CTX.
- Prosthetic: S. aureus and S. epidermidis — vanc + gentamicin + rifampin, and call ID the same hour.
- MSSA: an anti-staph β-lactam vastly outperforms vancomycin. Switch the minute MSSA is known.
- Early ID consult lowers mortality.
Bone, joint, no source
- Osteomyelitis (CID 2023;ciad527; ): hold antibiotics if stable, no cord compression, and a bone biopsy is coming. Empiric vanc + CTX; cefepime if DM/PAD ulcer or direct inoculation. Amp-sulbactam for bites.
- Septic arthritis: vanc + CTX (cefepime if PWID / Pseudomonas risk). Gonorrhea: CTX + doxycycline. Aspirate >50k WBC; ortho washout; cultures before drugs.
- Septic , no source: vanc + CTX or cefepime, or vanc + pip-tazo. MDRO worry: a carbapenem. TSS: add clindamycin or linezolid.