<i>Serratia</i> spp. Infections Outside An Outbreak Scenario: A Five-year Review of Patients in A University Hospital

Background: Serratia spp. are Gram-negative bacilli commonly found in soil and water, causing opportunistic infections particularly in hospital settings. Materials and Methods: A hospital review of patients hospitalized from 2017 to 2022 was made to identify patients whose clinical cultures grew Serratia spp. Inclusion criteria were age ≥18 years and isolation of one or more positive blood cultures for Serratia spp. Bacteremia was classified into two groups: Primary hospital-acquired bacteremia detected after 48 hours of hospitalization and bacteremia detected within the first 48 hours that was associated with previous healthcare facilities or applications. Results: During the study period, Serratia spp. were identified in blood cultures of 46 patients (52.7% males; mean age 60.7±17.6 years). Thirty-one patients (67.4%) had hospital-acquired bacteremia, while 15 patients had bacteremia acquired from previous healthcare facilities or applications. Thirty-five patients (76.1%) were infected by Serratia marcescens . All patients had predisposing risk factors for bacteremia, the most common being malignancies (n=19), followed by cardiac diseases (n=16), and diabetes mellitus (n=13). A history of antibiotic treatment in the past month was common (67.4%). Compared with patients who acquired bacteremia from previous healthcare facilities or applications, the rate of prior antibiotic use was significantly higher in patients with hospital-acquired bacteremia (p<0.01), so was the rate of appropriate empirical antibiotic use (p=0.01). Resistance to piperacillin/tazobactam was significantly more common among patients who acquired bacteremia from previous healthcare facilities or applications (p=0.02). Resistance to carbapenem in this group was also higher than expected (20%). During hospitalization, sepsis developed in 27 patients (58.7%). Within 30 days after laboratory detection of Serratia spp., mortality occurred in 16 patients (34.8%). Conclusion: The rate of healthcare-associated bacteremia is alarmingly high among hospitalized patients, which requires a meticulous inquiry into previous histories.