An Escalating Antimicrobial Resistance Crisis: Seven-Year Trends of Acinetobacter baumannii in a Tertiary Care Hospital in Pakistan

Background: Acinetobacter baumannii is a multidrug-resistant nosocomial pathogen classified as a critical priority organism by the WHO. Its persistence and adaptability pose serious treatment challenges, particularly in resource-limited settings such as Pakistan. Methods: A retrospective registry-based study was conducted in the Department of Microbiology at a tertiary care hospital covering the period from January 2017–December 2023. A total of 1,085 clinical isolates from patients aged 10–90 years were identified using standard microbiological techniques and API 20NE® (bioMérieux). Antimicrobial susceptibility testing was performed using the modified Kirby-Bauer disc diffusion method, as outlined in the CLSI guidelines. Susceptibility to colistin polymyxin B was determined using the broth microdilution method, according to CLSI guidelines. Data were analysed with Microsoft Excel 19.0. Results: The highest number of isolates occurred in 2018 (22.0%), with the lowest in 2021 (4.8%), likely reflecting the COVID-19 pandemic’s impact on healthcare utilization. ICU samples contributed nearly half of all isolates, highlighting the concentration of Acinetobacter infections in critical care. Resistance rates were alarmingly high: ciprofloxacin (88.8%), imipenem (88.1%), gentamicin (87.7%), and amikacin (84.5%). In contrast, colistin (97%), polymyxin B (96%), minocycline (70%), and tigecycline (71%) demonstrated the highest sensitivity. Infections were most frequent among patients aged 51–70 years. Conclusion: Acinetobacter baumannii shows extremely high resistance to most conventional antibiotics, including carbapenems and cephalosporins, leaving few therapeutic options. The ICU predominance and alarming resistance patterns underscore the urgent need for robust infection control strategies, antimicrobial stewardship, and continuous surveillance to mitigate the growing threat posed by this pathogen.