Objective
The epidemiology and bacteriology of MRSA infections in Scotland caused by ST398 isolates was examined

Methods
Isolates referred by Diagnostic Laboratories to the Scottish MRSA Reference Laboratory were reviewed. All such isolates are typed by MLST and those repeatedly giving no banding patterns with the restriction enzyme smaI were considered further. Antibiograms were obtained with the Vitek system (Biomerieux), SCCmec typing used the Oliviera primers and spa sequence was analysed using the Riddom software.

Results
In 2007 the Scottish MRSA Reference Laboratory carried out PFGE, using smaI on about 6,000 MRSA isolates referred by Diagnostic Laboratories and three were repeatedly found to be non-typeable. All three isolates were had identical PFGE patterns when the restriction enzyme apaI was used and all had the spa type t034. They were resistant to no antibiotic groups tested other then beta-lactams and, specifically, were sensitive to tetracyclines. They were SCCmec type III. Two of the isolates were typed by MLST and both were ST368. These features show them to be different from most reported ST398 isolates but isolates with similar antibiograms, spa types and SCCmec types have been reported from both Europe and Canada. All three patients had infections which responded to appropriate treatment. Epidemiological investigations of the patients, carried out by local hospital Infection Control Teams, were directed towards finding associations with pigs or pig farming but no such associations were found. The only link discovered was that all three had been in-patients in the same hospital, though not in the same ward or in the same department.

Conclusions
Three ST398 MRSA infections recognised in Scotland were all linked to the same hospital and no associations with pigs or pig farming are apparent.