Fifteen-Year Trends in Antimicrobial Resistance of Pseudomonas aeruginosa at a South Indian Tertiary Care Centre: A Retrospective Analysis.

BACKGROUND

Pseudomonas aeruginosa (P. aeruginosa) remains a major nosocomial pathogen with dynamic and evolving antimicrobial resistance (AMR) profiles, particularly in resource-constrained settings. This study aimed to analyse 15-year trends in antimicrobial susceptibility of P. aeruginosa isolates at a tertiary care centre in South India to inform local empiric therapy and stewardship strategies.

METHODS

A retrospective observational study was conducted between 2010 and 2024, analysing P. aeruginosa isolates from 54,208 clinical specimens. Isolates were identified using standard microbiological protocols, and antibiotic susceptibility was assessed by Kirby-Bauer disc diffusion, interpreted as per Clinical and Laboratory Standards Institute (CLSI) guidelines. Annual susceptibility rates were analysed using descriptive statistics and linear regression to assess temporal trends.

RESULTS

Among 17,517 culture-positive specimens, 2,225 (12.7%) were P. aeruginosa, predominantly from pus (52%) and respiratory samples (34.8%). Aminoglycosides (amikacin, tobramycin) exhibited the highest overall activity, with >70% susceptibility in later years. Significant improvements were observed in meropenem and piperacillin-tazobactam susceptibility over time, while imipenem showed a significant decline. Ceftazidime-avibactam, introduced in 2016, showed a steady increase to 51% in 2024. Conversely, imipenem demonstrated a significant decline (β = -0.83%/year, p = 0.0279). Ceftazidime, although initially low (3.5% in 2015), showed modest recovery by 2024 (32.2%).

CONCLUSION

Over 15 years, P. aeruginosa at this South Indian centre demonstrated both encouraging reversals in resistance to key β-lactam agents and concerning declines in others like imipenem. High and sustained aminoglycoside efficacy supports their selective use in empirical regimens. These findings highlight the critical role of ongoing local surveillance, antimicrobial stewardship, and integration of advanced diagnostics to combat evolving AMR in high-burden settings.