Pandrug-resistant (PDR) Klebsiella pneumoniae: Introduction

Introduction

Table of Contents

Organism: Gram-negative, encapsulated, facultative anaerobic, rod-shaped bacterium.
Epidemiology: Major cause of healthcare-associated infections (HAIs) like pneumonia, bloodstream infections, and UTIs.
PDR Definition: Non-susceptible to all antimicrobial agents across all clinical categories (beta-lactams, carbapenems, aminoglycosides, fluoroquinolones, polymyxins, and tigecycline).

Capsular Polysaccharide (CPS): Inhibits phagocytosis and complement-mediated killing.
Lipopolysaccharide (LPS): Acts as an endotoxin, triggering severe inflammatory responses.
Fimbriae (Types 1 & 3): Mediate adherence to host tissues and synthetic surfaces for biofilm formation.
Siderophores: Scavenge iron from host proteins to support bacterial metabolism.
Resistance Drivers: Driven by carbapenemase production (KPC, NDM, OXA-48), porin loss (OmpK35/36), and mgrB gene mutations (colistin resistance).

Microscopy: Gram-negative bacilli.
Culture: Large, pink, characteristically mucoid colonies on MacConkey agar due to lactose fermentation.

Biochemical Profile: Catalase-positive, oxidase-negative, indole-negative, citrate-positive, and urease-positive.
Susceptibility Testing: Handled via automated systems or broth microdilution (essential for colistin).
Molecular Diagnostics: PCR and Next-Generation Sequencing (NGS) for the isolation of specific carbapenemase genes.

High-Dose Synergy: Combining maximal drug doses via prolonged infusions (e.g., double carbapenems).
Novel Inhibitors: Aztreonam-avibactam or ceftazidime-avibactam combos (targeted to specific enzyme profiles).
Salvage Therapies: Use of novel agents like Cefiderocol or experimental bacteriophage therapy.

Hand Hygiene: Compliance with standard alcohol-based hand rub protocols.
Contact Isolation: Mandatory single-room isolation with dedicated gowns and gloves.
Decontamination: Intensive environmental disinfection of high-touch clinical surfaces.
Stewardship: Strict management of broad-spectrum and last-resort antibiotics.
Active Surveillance: Routine rectal swab screening to identify and isolate asymptomatic carriers.

PDR vs. XDR: Extensive drug resistance (XDR) leaves a few options; PDR leaves zero conventional choices.

Testing Pitfall: Disk diffusion is invalid for colistin testing; always request broth microdilution.
Hypervirulent Shift: Watch for “convergent” strains combining PDR with hypervirulence (hvKP), affecting healthy individuals.