P11 The ratio and antibiotic resistance profiles of Serratia species among other causative bacteria isolated from blood cultures between 2015 and 2020

BACKGROUND: Serratia spp., especially Serratia marcescens, have become one of the main drug-resistant causes of hospital infections in the last five decades.(1) There are a limited number of publications on Serratia spp., which cause sporadic infections or outbreaks in ICU patients, especially paediatric patients.(2) S. marcescens was reported to have intrinsic resistance to many β-lactam antibiotics, tetracyclines and polymyxins.(3–5) OBJECTIVES: To investigate the antibiotic resistance profiles of the Serratia spp. and detection rates among blood cultures. MATERIALS AND METHODS: This retrospective study was approved by Dicle University Medicine Faculty Non-Invasive Clinical Research Committee (no: 361, 1 September 2021). Blood culture samples sent from Dicle University Hospital clinics and ICUs between 2015 and 2020 were included. Blood culture samples were incubated in the BD BACTEC FX (Becton Dickinson, USA) system, and the isolates were identified at genus and/or species level by MS using the MALDI Biotyper 3 (Bruker Daltonics, USA). Antimicrobial susceptibility tests (AST) of the isolates were performed with the BD Phoenix 100 (Becton Dickinson, USA) automated system. AST results were interpreted according to the EUCAST criteria.(6) RESULTS: Among 9730 agents isolated from blood cultures over a 6 year period, 69 (0.7%) were identified as Serratia spp., 56 of them being S. marcescens (Table 1). Of patients from whom Serratia spp. were isolated, 37 (54%) were paediatric and 47 (68%) were ICU patients (Table 2). A total of 20 isolates (29%) were resistant to at least one of the carbapenems tested. The most effective antibiotics against Serratia spp. were found to be trimethoprim/sulfamethoxazole, ciprofloxacin and amikacin, with resistance rates of 3%, 4% and 7%, respectively (Table 3). CONCLUSIONS: Serratia species were isolated from blood cultures at a rate of 0.7% in a 6 year period, and increased carbapenem resistance among isolates was noteworthy.