A dominant strain of Elizabethkingia anophelis emerged from a hospital water system to cause a three-year outbreak in a respiratory care center

Abstract

Elizabethkingia species are ubiquitous bacteria but uncommonly cause human infection. An outbreak of Elizabethkingia anophelis bacteraemia was observed in a respiratory care center of a tertiary hospital in Taiwan from 2015 to 2018. Clinical and environmental isolates were collected for the outbreak investigation. Pulsed-field gel electrophoresis (PFGE) and complete-genome sequencing were conducted to elucidate the mechanism of transmission. The three-year outbreak involved 26 patients with E.anophelis bacteraemia and the incidence significantly increased during the outbreak period compared with that observed from 2010 to 2014 (P<0.05). All 26 clinical isolates during the outbreak period belonged to a cluster by PFGE analysis. In contrast, the PFGE pattern was heterogeneous among comparative historical strains. Hospital tap water was highly contaminated by Elizabethkingia species (18/34, 52.9%); among that, five E.anophelis belonged to the outbreak cluster (5/18, 27.8%). As for the inanimate surface survey, 3.4% sites (4/117) revealed positive growth of E.anophelis including two from feeding tubes/bags and two from sputum suction regulators. All four isolates belonged to the outbreak clone. The outbreak strain had no apparent relationship to currently known E.anophelis strains worldwide through complete-genome sequencing analysis. Specific infection control strategies aimed at water source control and environmental disinfection were implemented subsequently and the outbreak ended in mid-2018. A specific E.anophelis strain was identified from a three-year outbreak. The elucidation of the mechanism of dominance and intra-hospital transmission is crucial for development of corresponsive infection control policies and outbreak control.