A Longitudinal Study on Antimicrobial Resistance Dynamics in Pseudomonas aeruginosa at a Government Superspeciality Hospital

Introduction: Pseudomonas aeruginosa, primarily an opportunistic hospital pathogen, has now become an increasing cause of infections in the community as well. It significantly contributes to the rising burden of Antimicrobial Resistance (AMR), making treatment challenging. In high-risk settings such as superspeciality hospitals, the impact of AMR is magnified, necessitating continuous surveillance of susceptibility patterns to guide empirical therapy and escalation/de-escalation strategies for definitive treatment as part of antimicrobial stewardship. Aim: To analyse the Antimicrobial Susceptibility Testing (AST) patterns of Pseudomonas aeruginosa isolates at a government superspeciality hospital. Materials and Methods: This longitudinal study analysed data from three years (January 2021 - January 2024) at the 250-bedded ESIC super-speciality government teaching hospital, Hyderabad , Telangana, India. Adhering to Clinical and Laboratory Standards Institute (CLSI) M-100 guidelines, samples were collected and processed on clinical requests; those showing growth were analysed using an automated identification and AST analyser. Among all the samples received in the microbiology laboratory, 517 samples with growth of Pseudomonas aeruginosa were included. Colistin resistance was confirmed using Colistin Broth Disc Elution (CBDE) and compared with automated analyser results to assess the difference between both methods. Suitable antibiotics with potential for treatment were evaluated based on CLSI M39 guidelines. Demographic parameters such as age groups (paediatric and adult), gender distribution and sample types (urine, blood, respiratory specimens and exudates) were considered to evaluate resistance patterns. Descriptive statistics were used and presented in terms of percentages. Results: In the current study, among the 517 isolates of Pseudomonas aeruginosa, 440 (85%) were from adults and 77 (15%) from paediatric population. Pseudomonas aeruginosa showed varying susceptibility rates to different antibiotics, ranging from 193 (43.8%) to 276 (62.7%) in adults and 32 (41.5%) to 38 (49.3%) in paediatric population. Multidrug Resistant (MDR) isolates totalled 170 (32.8%), with 123 (43.2%), 6 (12.5%), 20 (22.1%) and 21 (22.5%) among the received urine, blood, respiratory and exudate samples, respectively. MDR Pseudomonas aeruginosa rates increased from 2021 to 2023, reaching 68 (43.6%). Colistin susceptibility rates were relatively better, with 371 (84.3%) in adults and 70 (90.9%) in the paediatric population. Colistin susceptibility ranged from 38 (79%) to 83 (93%) across samples. A discrepancy of 76 (14.7%) was observed between the CBDE and automated methods for detecting colistin resistance. Conclusion: This study highlights the increase in MDR Pseudomonas aeruginosa, with higher resistant rates observed among paediatric population. While colistin remains effective, its resistance requires ongoing monitoring, necessitating the need for alternative strategies, enhanced infection control measures and antimicrobial stewardship to effectively combat the growing threat of AMR in Pseudomonas aeruginosa.