Introduction / objectives
Although MRSA outbreaks might have significant consequences on patients and/or health care resources, few data are available about the microevolution of a strain during a single outbreak. In this study, our aim was to characterize the variability of accessory genes among isolates recovered during a local MRSA outbreak.
Ten MRSA isolates recovered during a large outbreak occurring at the Lausanne University Hospital (Switzerland) were characterized using a DNA microarray (StaphyType, Alere Technologies, Germany) that targets approximately 180 genes including several resistance and virulence genes. Each isolate belonged to the South German clone (ST-228-SCCmec I) and had been recovered between September 2008 and December 2009.
As expected during the clonal dissemination of a strain, the 10 isolates shared identical presence/absence for most of the c.a. 180 genes tested. Nevertheless, variation was observed for several resistance and virulence genes. These included the beta lactamase operon genes (blaZ, blaI, blaR), genes involved in the resistance to Trimethoprim and Mupirocin (dfrA and mupR, respectively), a gene encoding unspecific efflux pump conferring resistance to a variety of antiseptic such as chlorhexidine (qacA), and genes potentially involved in virulence (lukX, lukY, aur). This variability affected at least 5 of the ten isolates.
Our results indicate the gain/loss of resistance and virulence genes during a local outbreak, suggesting that the biological characteristics of the strain might vary through time.
Disclosure of interest