Persistence of a major endemic clone of oxacillin-resistant Staphylococcus lugdunensis sequence type 6 at a tertiary medical centre in northern Taiwan

Objectives: The aim of this study was to investigate the molecular epidemiology and clinical characteristics of a major clone of oxacillin-resistant Staphylococcus lugdunensis in a tertiary hospital. Methods: All S. lugdunensis isolated from sterile sites between June 2003 and May 2013 were collected for analysis. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed to study their genetic relationships. Results: A total of 118 S. lugdunensis isolates were analysed by PFGE. Three major PFGE pulsotypes were found: A, H, and L. Most of the pulsotype A isolates were oxacillin-resistant, and SCC. mec type V and type VT. Isolates from another major clonal group that consisted primarily of pulsotype L were oxacillin-resistant and SCC. mec type II. These 14 SCC. mec type II S. lugdunensis isolates demonstrated high PFGE similarity and were obtained in the study hospital over a period of 40 months. Three of these 14 patients had clinically significant bacteraemia, and all three cases were in the intensive care unit. Further MLST analysis of the isolates identified an endemic S. lugdunensis strain of sequence type 6, clonal complex 1. Conclusions: This study identified a major endemic clone of S. lugdunensis that is oxacillin-resistant, SCC. mec type II, ST6, and capable of long-term persistence in the hospital. Continuous infection control surveillance and monitoring of S. lugdunensis should be considered in endemic areas.