Antimicrobial Resistance Profile and Longitudinal Trends of Morganella morganii Clinical Isolates in a University Hospital

Objectives: Morganella morganii is an opportunistic Gram-negative pathogen increasingly associated with healthcare-associated infections and antimicrobial resistance. However, long-term epidemiological data from Türkiye remain scarce.
Methods: This retrospective study analyzed M. morganii isolates obtained between January 2015 and December 2024 at a 1500-bed tertiary care hospital. Demographic data, clinical specimen sources, and antimicrobial susceptibility results were retrieved from the laboratory database. Identification was performed using conventional methods and MALDI-TOF MS, while antimicrobial susceptibility was determined according to EUCAST guidelines. Linear regression analysis was applied to evaluate resistance trends over time.
Results: A total of 673 non-duplicate isolates were included, predominantly from urine (68.6%), followed by wound (19.2%), blood (4.7%), respiratory (3.6%), abscess (1.9%), and sterile body fluid (1.0%) specimens. The annual incidence ranged from 0.47% in 2015 to 1.9% in 2024, with a transient decline during 2020–2022, likely related to the COVID-19 pandemic. Male patients accounted for 63% of isolates, with a median age of 52 years. Meropenem and amikacin showed the highest overall activity (>98% susceptibility), while cefoxitin demonstrated the lowest efficacy (≈50%). Trend analysis revealed statistically significant increases in resistance to amikacin, imipenem, meropenem, ertapenem, ceftriaxone, ceftazidime, cefoxitin, cefepime, piperacillin–tazobactam, trimethoprim–sulfamethoxazole, and ciprofloxacin (all p<0.05), whereas gentamicin showed no significant change. Notably, carbapenem and aminoglycoside resistance increased markedly after 2022.
Conclusion: This study highlights the rising clinical importance of M. morganii, with increasing resistance across multiple antibiotic classes, including carbapenems. The findings underscore the need for continuous surveillance, prudent antimicrobial use, and further genomic studies to elucidate resistance mechanisms and guide effective therapy.

Keywords: Antimicrobial resistance, carbapenem resistance, epidemiology, Morganella morganii