Clinical features, outcomes, and molecular characteristics of an outbreak of Staphylococcus haemolyticus infection, among a mass-burn casualty patient group, in a tertiary center in northern Taiwan

Abstract

Background/purpose: We reported an outbreak of Staphylococcus haemolyticus (SH) infection in a group of young patients (mean age 21.6) simultaneously hospitalized due to a mass-burn incident. This study analyzed the clinical features of these patients and the microbiological characteristics of the outbreak. Methods: All 50 patients hospitalized for burns were enrolled, and their clinical differences were analyzed based on culture results. A drug sensitivity test and pulsed-field gel electrophoresis (PFGE) were conducted to analyze the microbiological difference between SH isolates from the mass-burn casualty patients (the study group) and SH isolates from other patients hospitalized during the same period (the control group) with the intention of identifying the strain of SH outbreak. Results: Patients with isolated SH (N = 36) had a significantly higher disease severity (higher revised Baux score, APACHE II score, and concurrent bacteremia rate), and a significantly poorer clinical outcome (longer ICU and hospital stay, and longer MV usage). Significant differences in the phenotype (antibiotics drug sensitivity test) and genotype (PFGE typing) were observed between the study and control groups. The dominant PFGE type C identified among the study group was related to poorer outcomes in a subgroup analysis. Conclusion: A dominant PFGE type of SH infection was found in these mass-burn casualty patients. Pathogenesis or virulence factors may have contributed to our results. Further study of isolated SH should be conducted. Keywords: Burn, Outbreak, Outcome, Pulsed-field gel electrophoresis (PFGE), Staphylococcus haemolyticus (SH)