168.1 🎓 醫孞生版

168.1.0.1 📌 䞀頁重點

  • Klebsiella pneumoniae:
    • Classic strain (cKp): nosocomial, UTI, pneumonia, bacteremia, CRE-KPC (US/Israel) / IMP/NDM (Asia)
    • Hypervirulent strain (hvKp): K1/K2 capsule, Taiwan/Asia DM + liver abscess + endophthalmitis + meningitis; string test +
  • Klebsiella oxytoca: antibiotic-associated hemorrhagic colitis (AAHC)
  • Klebsiella granulomatis: granuloma inguinale (donovanosis)
  • Enterobacter cloacae complex: AmpC inducible, nosocomial
  • Citrobacter: AmpC, neonatal meningitis (C. koseri brain abscess)
  • Serratia marcescens: AmpC, red pigment, IV drug user IE, contamination outbreaks
  • Hafnia, Edwardsiella: rare
  • Yersinia enterocolitica, Y. pseudotuberculosis, Y. pestis: see Ch 174
  • 抗藥: ESBL, AmpC, CRE — see Ch 167

168.1.0.2 1⃣ Klebsiella

168.1.0.2.1 A. Classic Strain (cKp) — Nosocomial Profile
  • Gram - rod, lactose +, mucoid colonies (capsule)
  • Source: gut + skin commensal; HAP, VAP, line, UTI
  • FriedlÀnder’s pneumonia (alcoholic, upper lobe, “currant jelly sputum”, cavitation)
  • UTI in catheter / immunocompromise
  • CRE 倧問題: KPC plasmid in K. pneumoniae 䞻芁 USA; IMP / NDM 圚 Asia
168.1.0.2.2 B. Hypervirulent Klebsiella (hvKp)
  • Taiwan / Asia endemic (50% Taiwan liver abscess from hvKp K1)
  • K1 + K2 capsular types (hypermucoviscous)
  • Plasmid carries virulence (iroBCDEN, rmpA, magA — siderophore + mucoid regulator)
  • String test +: bacteria colony 拉出 > 5 mm string on plate
  • Pyogenic liver abscess (PLA):
    • 糖尿病人 strong association
    • Monomicrobial (vs cryptogenic / polymicrobial in West)
    • Multiple complications: endophthalmitis (倱明 急!), meningitis, lung abscess, brain abscess
    • 圱像: hypodense liver lesion + gas
    • Tx: drainage + IV ceftriaxone (or ertapenem) × 6+ weeks
    • 慎防 hematogenous spread
  • Non-liver presentations:
    • Community-acquired meningitis (糖尿病人)
    • Brain abscess
    • Endophthalmitis (sometimes 先 ocular sx 䞍倪認埗是 endogenous)
    • Pneumonia + lung abscess (community)
    • Skin/soft tissue (necrotizing fasciitis)
    • SBP (cirrhotic)
168.1.0.2.3 C. Klebsiella oxytoca — AAHC
  • Antibiotic-associated hemorrhagic colitis
  • Penicillin / β-lactam exposure → enterotoxin (tilivalline, tilimycin)
  • 血䟿 + abdominal pain + 短 course (days)
  • 取代 PCN → resolution; 䞍 CDI mimicker
168.1.0.2.4 D. Klebsiella granulomatis (Donovanosis)
  • 熱垶 STI
  • Painless beefy granuloma genital
  • “Donovan bodies” intracellular (Wright stain)
  • Tx: azithromycin × 3 wk or doxycycline × 3 wk
168.1.0.2.5 E. Klebsiella aerogenes (formerly Enterobacter)
  • 重新 園 Klebsiella 2016
  • Same AmpC inducible
  • Similar treat to Enterobacter

168.1.0.3 2⃣ Enterobacter cloacae complex

  • Gram - rod, lactose +
  • AmpC β-lactamase chromosomal inducible
  • Nosocomial: pneumonia (HAP), UTI, bacteremia, intra-abdominal, line
  • Critical care / immunocompromised
  • Risk: prior 3rd-gen ceph exposure
168.1.0.3.1 Treatment
  • Cefepime (4th gen, stable to AmpC)
  • Carbapenem (severe, ICU, bacteremia)
  • FQ (if susceptible)
  • Avoid ceftriaxone monotherapy — induces resistance during therapy (10-30% emergence)
  • AmpC complex includes: E. cloacae, E. asburiae, E. hormaechei, E. kobei, E. ludwigii
168.1.0.3.2 Risk Stratification (2023 IDSA AMR Guidance)
  • Bacteremia + AmpC-producer → carbapenem
  • Mild source (cystitis) → cefepime / FQ OK

168.1.0.4 3⃣ Citrobacter

168.1.0.4.1 Species
  • C. freundii complex: AmpC inducible (similar to Enterobacter)
  • C. koseri (formerly C. diversus): neonatal meningitis + brain abscess — distinctive
168.1.0.4.2 臚床
  • UTI, intra-abdominal, line bacteremia
  • C. koseri neonatal — > 70% brain abscess (mortality / morbidity high)
168.1.0.4.3 Treatment
  • C. freundii: cefepime / carbapenem (AmpC)
  • C. koseri (neonatal meningitis): cefepime / meropenem; long course

168.1.0.5 4⃣ Serratia marcescens

168.1.0.5.1 特埵
  • Gram - rod, lactose - (some), red pigment (prodigiosin) at room temp
  • AmpC similar (less inducible than Enterobacter but still concern)
168.1.0.5.2 流行病孞
  • Nosocomial outbreaks — contaminated solution, eye drops, total parenteral nutrition, dialysis water
  • IVDU IE (S. marcescens + 其他)
  • UTI, line bacteremia, pneumonia (VAP)
  • Neonatal sepsis / meningitis
168.1.0.5.3 Treatment
  • Cefepime / carbapenem
  • FQ if susceptible
  • Source control: contaminated equipment

168.1.0.6 5⃣ Other Enterobacterales (Brief)

168.1.0.6.1 Hafnia alvei
  • 倚 commensal; opportunist; usually mild
  • Cefotaxime / cefepime
168.1.0.6.2 Edwardsiella tarda
  • Fresh water (catfish handlers); GI + bacteremia
  • 3rd-gen ceph
168.1.0.6.3 Pantoea
  • Plant + soil; line + contamination outbreaks
  • 3rd-gen ceph
168.1.0.6.4 Cronobacter sakazakii
  • Powdered infant formula contamination
  • Neonatal meningitis + sepsis
  • High mortality; ampicillin + gentamicin / meropenem
168.1.0.6.5 Plesiomonas shigelloides
  • Freshwater / seafood diarrhea (mild dysentery)
  • FQ or TMP-SMX if severe; otherwise self-limit

168.1.0.7 6⃣ 敎合 Treatment

168.1.0.7.1 Empirical (Pending Culture)
  • CAP: ceftriaxone + azithro (or FQ); 䞍必 cover Klebsiella unless cavitary / alcoholic
  • HAP/VAP: pip-tazo + vanco; broader if MDR risk
  • UTI / pyelo (community): ceftriaxone
  • UTI HCAP: cefepime + vanco; carbapenem if ESBL risk
  • Bacteremia ICU: cefepime + vanco; carbapenem + vanco if MDR risk
  • Intra-abd nosocomial: pip-tazo + vanco; broader if MDR
168.1.0.7.2 Targeted (After Susceptibility)
  • AmpC + (Enterobacter, Citrobacter, Serratia): cefepime first; severe → carbapenem
  • ESBL: carbapenem (severe); fosfomycin/nitro (cystitis)
  • CRE: see Ch 167 detail (CAZ-AVI, cefiderocol)
  • Hypervirulent K. pneumoniae liver abscess: ceftriaxone or ertapenem + drainage × 6+ wk