Wound infections caused by Serratia marcescens: a microbiology survey

INTRODUCTION: Serratia marcescens wound infections are a concern in healthcare settings, associated with delayed healing, prolonged hospital stays, higher costs, and sepsis in severe cases. AIM: This study aimed to evaluate the antimicrobial susceptibility of S. marcescens wound isolates from patients in St. Marina University Hospital, Varna, Bulgaria (2016–2023) and to explore the genetic mechanisms responsible for the 3 rd generation cephalosporin resistance in these isolates. MATERIALS AND METHODS : Over the 8-year period, 131 isolates were collected. Identification and antimicrobial susceptibility testing were performed using Phoenix (BD, USA) and Vitek 2 (BioMerieux, France), with results interpreted by EUCAST guidelines. The genetic mechanisms responsible for beta-lactam resistance were studied by PCR. RESULTS : A total of 98.5% of the patients were diagnosed with nosocomial S. marcescens infections. Diabetes and a cardiovascular disease were found as accompanying risk factors in 42.8% and 71%, respectively. Resistance rates were: ceftriaxone—14.5%; gentamicin—13.7%; cefepime/trimethoprim-sulfamethoxazole—12.9%, and ciprofloxacin/levofloxacin—12.2%. No carbapenem resistance was found. Bla CTX-M was present in 72.7% of cephalosporin-resistant isolates. CONCLUSION : S. marcescens remains a significant nosocomial pathogen, with less than 15% resistance to main antimicrobials. We found the leading role of bla CTX-M for the 3 rd generation cephalosporin resistance in S. marcescens , confirming the global trends.