Phenotypic profiling of Carbapenem drug resistant Pseudomonas species in a tertiary care hospital in Tamilnadu

Abstract

Background: Pseudomonas aeruginosa, an opportunistic pathogen, is a leading cause of healthcare-associated infections, particularly in immunocompromised individuals. The emergence of carbapenem-resistant strains poses major therapeutic and infection control challenges. Identifying carbapenem resistance through reliable phenotypic methods is essential for guiding infection control and antimicrobial stewardship.

Aim and Objectives: To characterize carbapenem-resistant Pseudomonas isolates from various clinical specimens using standard phenotypic methods and to assess specimen-specific resistance patterns for optimizing antibiotic use and diagnostic accuracy.

Materials and Methods: A cross-sectional study was conducted from May to October 2024 at a tertiary care hospital. A total of 100 Pseudomonas isolates from blood, pus, urine, wound swabs, respiratory secretions, cerebrospinal fluid, and other sterile body fluids were tested. Identification was done by standard biochemical tests, and antimicrobial susceptibility was determined by Kirby-Bauer disc diffusion following CLSI 2021 guidelines. Carbapenem resistance was confirmed using imipenem and meropenem discs, and results were validated by the VITEK automated system.

Results: Out of 100 isolates, 10% and 9% showed resistance to imipenem and meropenem respectively with a collective carbapenem resistance of 10%. Pus specimens displayed the highest resistance (28% IPM, 24% MRP; p < 0.05), while isolates from blood, respiratory, and CSF samples remained fully susceptible. VITEK confirmed all isolates as carbapenem-sensitive, revealing complete discordance (κ = 0.00) with disc diffusion.

Conclusion: Most Pseudomonas isolates retain high susceptibility to multiple antibiotic classes. Carbapenem resistance was limited, emphasizing confirmatory testing, specimen-specific surveillance, and antimicrobial stewardship to prevent resistance escalation.