175.1 🎓 醫孞生版

175.1.0.1 📌 䞀頁重點

  • 菌: Pseudomonas aeruginosa — Gram - aerobic rod, oxidase +, non-lactose fermenter, pyocyanin (green-blue pigment), pyoverdine (yellow-green), grape-like odor
  • Habitat: ubiquitous water + soil + biofilms (medical equipment, sink, drain, ICU)
  • Risk hosts:
    • Cystic fibrosis (chronic colonization → bronchiectasis decline)
    • Burn (skin barrier breach + biofilm)
    • Neutropenic (chemotherapy / BMT)
    • HIV / immunocompromise
    • Catheter / device (Foley, central line, vent, prosthetic)
    • Diabetic foot, malignant otitis externa
    • ICU/hospital patients
  • Multi-syndrome: pneumonia (VAP), bacteremia/sepsis, endocarditis (IDU TV), UTI, SSTI (ecthyma gangrenosum), osteo (sneaker stab), malignant otitis externa (DM elderly), eye (contact lens keratitis)
  • 倚重抗藥機蜉: β-lactamase, AmpC, porin loss (OprD), efflux (MexAB-OprM), target modification
  • Antibiotics with PsA cover:
    • β-lactam: piperacillin-tazobactam, ceftazidime, cefepime, aztreonam, carbapenem (imi/mero/dori — not ertapenem)
    • Aminoglycoside (amikacin > gent > tobra)
    • FQ (cipro, levo — but high R)
    • Colistin (last resort)
    • Newer: ceftolozane-tazobactam, CAZ-AVI, imipenem-relebactam, cefiderocol

175.1.0.2 1⃣ 现菌孞

  • Gram - rod, motile (polar flagellum)
  • Strict aerobe
  • Oxidase + (vs Enterobacterales -)
  • Non-lactose fermenter
  • Pyocyanin blue-green pigment + pyoverdine yellow-green fluorescent pigment → “rainbow” appearance
  • Grape-like / 玫瑰 odor (2-aminoacetophenone)
  • Biofilm-forming (CF lungs, catheter, prosthetic — chronic + R)
175.1.0.2.1 Virulence
  • Type III secretion (ExoS, ExoT, ExoU, ExoY) — host cell killing
  • Exotoxin A — ADP-ribosylates EF-2 (like diphtheria)
  • Alginate (CF mucoid) — biofilm + immune evasion
  • Phospholipase, elastase, protease
  • Quorum sensing (las, rhl) — coordinates virulence
175.1.0.2.2 MDR Mechanisms
  • AmpC β-lactamase (chromosomal)
  • Acquired ESBL/MBLs (KPC, VIM, IMP, NDM)
  • Porin loss (OprD) → carbapenem R
  • Efflux pumps (MexAB-OprM, MexXY-OprM) → multi-drug
  • gyrA/parC mutations → FQ R
  • Target modification (16S rRNA methylase → aminoglycoside R)

175.1.0.3 2⃣ 臚床衚珟

175.1.0.3.1 A. Hospital-Acquired Pneumonia (HAP) / VAP
  • Common in vent / ICU
  • Acute onset, severe, often cavitary
  • Bilateral / multilobar
  • Empirical: pip-tazo or cefepime ± aminoglycoside (severe), then de-escalate
  • CF chronic: mucoid → bronchiectasis, FEV1 decline
175.1.0.3.2 B. Bacteremia / Sepsis
  • Septicemia in neutropenic / immunocompromise
  • High mortality
  • Ecthyma gangrenosum classic sign (necrotic ulcer with black eschar, often legs)
175.1.0.3.3 C. Endocarditis
  • IVDU — tricuspid valve primarily
  • Also prosthetic valve
  • Treatment: pip-tazo / ceftazidime + aminoglycoside × 6 wk; surgery if 倱敗
175.1.0.3.4 D. UTI
  • Catheter, post-instrumentation
  • Resolve with catheter removal + antibiotic
175.1.0.3.5 E. Skin / Soft Tissue
  • Burn wound (#1 colonizer)
  • Folliculitis / hot tub folliculitis (contaminated hot tub, self-limited)
  • “Green nail” (paronychia + green pigment)
175.1.0.3.6 F. Diabetic Foot
  • Polymicrobial; PsA in ~ 20-30%
  • Treatment: pip-tazo + vanco; debridement
175.1.0.3.7 G. Malignant Otitis Externa (Necrotizing OE)
  • Elderly DM classic
  • Severe ear pain + drainage + granulation tissue in canal
  • Can progress to skull base osteo, CN VII palsy, intracranial extension
  • MRI / Tc-99m bone scan
  • Treatment: 6-8 wk IV pip-tazo / ceftazidime / cipro (high oral bioavail)
175.1.0.3.8 H. Osteomyelitis
  • Puncture wound through sneaker → calcaneus / metatarsal
  • Chronic OM in CF, IDU
  • Cipro PO often used due bioavail (when susceptible)
175.1.0.3.9 I. Eye
  • Contact lens keratitis — rapid corneal ulcer, can perforate within days
  • Treatment: topical fortified ciprofloxacin or tobramycin; emergency
175.1.0.3.10 J. Hot Tub Folliculitis
  • Pruritic papule pustular rash on body submerged
  • Self-limited, no antibiotic usually

175.1.0.4 3⃣ 治療 — Empirical + Targeted

175.1.0.4.1 Empirical (Hospital, Severe)
  • Combination therapy controversial but common in severe:
    • β-lactam (pip-tazo, cefepime, ceftazidime, mero) + aminoglycoside (until S known)
    • Goal: cover R + rapid bacterial kill in septic shock
    • De-escalate to monotherapy once susceptibility known (mono = OK in most situations per Heyland 2008, AVD 2014 RCTs)
175.1.0.4.2 MDR Pseudomonas
  • Difficult-to-treat (DTR-PsA) — non-S to all 1st-line β-lactams + FQ + carbapenem
  • CAZ-AVI (ceftazidime-avibactam) — KPC, AmpC, ESBL
  • Ceftolozane-tazobactam — ESBL, AmpC, some MDR PsA
  • Imipenem-relebactam — KPC, MDR PsA
  • Cefiderocol — all (siderophore Trojan horse)
  • Colistin (last-resort, nephrotoxic + neurotoxic)
  • Aminoglycoside (high-dose)
  • Fosfomycin IV (UTI / abdominal)
175.1.0.4.3 CF Specific
  • Chronic suppression: inhaled tobramycin / aztreonam / colistin
  • Exacerbation: IV pip-tazo + tobramycin OR ceftazidime + tobra × 14d
  • Eradication early colonization: PE WALK trial — inhaled tobra for 28d
175.1.0.4.4 Endocarditis
  • High-dose β-lactam + aminoglycoside × 6 wk
  • Surgery if 倱敗 / large vegetation
175.1.0.4.5 Malignant Otitis Externa
  • 6-8 wk IV
  • Often pip-tazo + cipro PO step-down
  • HBO adjunct controversial