Evolutionary trends in antibiotic resistance of Pseudomonas aeruginosa and Acinetobacter baumannii before and during the COVID-19 pandemic

Background: Acinetobacter baumannii and Pseudomonas aeruginosa are major causes of healthcare-associated infections and are frequently associated with multidrug resistance. This study aimed to analyze the evolution of antibiotic resistance in Acinetobacter baumannii and Pseudomonas aeruginosa at a Moroccan hospital between 2017 and 2023, with particular focus on the potential impact of the COVID-19 pandemic. Methods: We conducted a retrospective study from January 2017 to December 2023 at the Bacteriology Department of Mohammed V Military Teaching Hospital, Rabat, Morocco. Non-redundant isolates of A. baumannii and P. aeruginosa were identified using conventional methods. Antimicrobial susceptibility was determined by disk diffusion according to CASFM/EUCAST guidelines. Colistin susceptibility was assessed using broth microdilution. Pre-pandemic (2017–2019) and pandemic (2020–2023) resistance rates were compared. Results: A total of 5054 non-redundant isolates were recovered from 4803 patients, including 2840 (56%) P. aeruginosa and 2214 (44%) A. baumannii. During the pandemic, A. baumannii isolates showed significant increases in resistance to amikacin (86% vs. 68%), ceftazidime (95% vs. 87%), ciprofloxacin (93% vs. 89%), imipenem (92% vs. 83%), piperacillin-tazobactam (93% vs. 88%), and tobramycin (74% vs. 58%) (all p < 0.05). Similarly, P. aeruginosa isolates exhibited increased resistance to amikacin (24% vs. 18%), ceftazidime (45% vs. 19%), ciprofloxacin (51% vs. 24%), imipenem (44% vs. 21%), piperacillin-tazobactam (42% vs. 15%), and tobramycin (25% vs. 17%) (all p < 0.05). Colistin resistance remained absent (0%) in both species. Conclusion: Resistance rates in A. baumannii and P. aeruginosa significantly increased during the COVID-19 pandemic, reducing therapeutic options.