Objectives:

To follow-up the discovery of an EMRSA15 isolate carrying the PVL gene, commonly associated with community-acquired MRSA, by searching the Scottish MRSA Reference Laboratory (SMRL) collection of MRSA isolates. Unlike many hospital strains, EMRSA15 usually carries few additional resistances and has the type IV SCCmec element but isolates have not, to our knowledge, been previously reported to carry the PVL gene.

Methods:

A clinical microbiologist had drawn to our attention an MRSA isolate from a 6-month-old child who had suffered recurrent infections suggestive of a PVL-producing strain but who was otherwise healthy. This MRSA was shown by PCR to have the PVL gene, the mecA gene and the type-IV SCCmec element; phenotypically it appeared to be an EMRSA15 with an unusual antibiogram. The PFGE-banding pattern of the isolate varied from the commonest EMRSA15 pattern at only one band locus; the change was indicative of an insertion event. We searched the SMRL database for phenotypically and genotypically related isolates, tested them by PCR and further characterised isolates with the PVL gene.

Results:

Less than 0.1% of the approximately 30 000 EMRSA15 isolates in our database had the same antibiogram as the index isolate; 21 of these were tested for the PVL gene and 20 were positive. By PFGE, all the PVL-positive isolates had patterns typical of EMRSA15; all had the apparent insertion seen in the index isolate but there was some other variation between the patterns. Most of the PVL-positive isolates had the same, uncommon, phage pattern though three were untypable. The earliest isolate had been received in 1998 and the sending laboratories were from several different geographical regions of Scotland. PCR testing for other toxin genes on five of the isolates has shown that they also carry the enterotoxin C gene, like most other EMRSA15 isolates that we have tested. We have also examined about 60 EMRSA15 isolates identified from our database as similar to the index isolate, but not identical, and all were PVL-negative by PCR; none of the individual recognisable characteristics (susceptibility markers, phage type, PFGE insertion) alone are markers for the PVL gene.

Conclusions:

We have shown that a phenotypically identifiable group of EMRSA15 isolates carrying the PVL gene has been circulating in Scotland for at least 5 years.