Morphology: Non-lactose-fermenting gram-negative rod, oxidase-positive, grape-like odor, blue-green pigment.
PseudomonasGramNegOther
Typical drugs
- #1Piperacillin-tazobactam
- #2Cefepime
- #3Meropenem— Multidrug-resistant or severe.
- #4Ciprofloxacin— Step-down PO if susceptible.
Empiric therapy when resistant
Use 2 anti-pseudomonal agents from different classes if severely ill (e.g., cefepime + tobramycin). De-escalate to 1 once susceptibilities back.
Resistance mechanisms
Permeability / porin
Decreased OprD porin
Example: Carbapenem resistance.
Efflux pump
MexAB-OprM efflux pumps
Example: Multidrug resistance.
Enzymatic degradation
AmpC β-lactamases
Example: Inducible during therapy.
Resistance notes
Develops resistance during therapy via AmpC induction. Avoid monotherapy with weakly active β-lactams.
Pearls
Risk factors for empiric coverage: structural lung disease, recent hospitalization, neutropenia, recent IV abx (90d).
References
- IDSA HAP/VAP (2016)