176.1 🎓 醫學生版

菌: Acinetobacter baumannii (most clinical), A. lwoffii, A. junii — Gram - coccobacilli, aerobic, oxidase NEG (vs PsA +), non-lactose, non-motile
Habitat: soil + water + skin commensal; hospital ICU + ventilator survives long on dry surfaces (1 month+)
WHO critical priority (2024)
流行病學:
- ICU / VAP / ventilator main
- Burn, trauma (戰場 wound — Iraq/Afghanistan, Ukraine 2022+)
- Catheter / line / device
- Skin colonization → bacteremia
臨床: VAP / HAP (#1 syndrome), bacteremia, UTI, wound/SSTI, meningitis (post-neurosurgery / shunt)
MDR / XDR / PDR profile: > Pseudomonas; resists almost all antibiotics
抗藥機轉: OXA carbapenemases (OXA-23, OXA-24, OXA-58 主要), AmpC overexpression, porin loss, efflux pumps, NDM
Treatment (2023 IDSA AMR):
- Sulbactam-durlobactam (Xacduro, 2023 FDA) — game changer for CRAB; combined with imipenem (usually)
- Cefiderocol (siderophore Trojan horse)
- High-dose ampicillin-sulbactam (sulbactam has intrinsic Acinetobacter activity)
- Combination: high-dose meropenem + colistin (or polymyxin B) + tigecycline / minocycline ± aminoglycoside
- Single-drug therapy 失敗 routinely — combination 常用

Gram - coccobacillus
易誤認為 gram + cocci on smear (重點 distinguish)
Oxidase NEGATIVE (區分 from Pseudomonas oxidase +)
Strict aerobic
Non-lactose, non-motile
Glucose oxidation only (some), 多 inert biochemically
A. baumannii complex (ACB complex) most clinical — includes A. baumannii, A. nosocomialis, A. pittii (難 distinguish phenotype)
Survives 4 weeks+ on dry surface → environmental reservoir

Asia, especially tropical (Thailand, Australia northern) — severe seasonal CAP
Healthy young adult, rapid course
Multi-lobar consolidation
High mortality

OXA carbapenemases (OXA-23, OXA-24/40, OXA-58, OXA-72) — Acinetobacter-specific, plasmid + chromosomal
NDM, IMP, VIM (metallo β-lactamases — Asia)
AmpC overexpression
Porin loss (OmpA, CarO)
Efflux pumps (AdeABC)
PBP modification
16S rRNA methylase → aminoglycoside R
gyrA/parC → FQ R
mcr-1, lpxA mutations → colistin R (rare but emerging)

Sulbactam-durlobactam (Xacduro, FDA 2023) + imipenem — first-line for serious CRAB
Cefiderocol — alternative, especially metallo β-lactamase
High-dose ampicillin-sulbactam (9 g IV q8h) — sulbactam activity, often part of combination
Polymyxin B / Colistin — last-resort, nephrotoxicity + neurotoxicity, often combination
Tigecycline / Minocycline — not bacteremia/UTI (low conc)
Eravacycline — alternative
High-dose tobramycin / amikacin — adjunctive
Combination therapy common (no single drug enough in PDR)