Characterisation of methicillin-resistant Staphylococcus aureus by biotyping, immunoblotting and restriction enzyme fragmentation patterns.

We have characterised 45 isolates of methicillin-resistant Staphylococcus aureus (MRSA) from Glasgow Royal Infirmary by means of simple biotyping, immunoblotting of exported proteins and restriction enzyme fragmentation patterns (REFP) of plasmid DNA. The strains were subdivided into four groups (A-D) on the basis of biotype. Immunoblotting and restriction enzyme fragmentation generated a number of unique patterns. Analysis of these patterns by means of Dice coefficients of similarity separated them into two major immunoblot groups (Blot1 and Blot2) and two major REFP groups (FP1 and FP2). There was strong positive correlation between Blot1 and FP1 groups and between Blot2 and FP2 groups. In addition, Blot1-FP1 isolates were almost exclusively of biotypes A or C, whereas Blot2-FP2 isolates were of biotypes B or D. The methods described here have provided comprehensive epidemiological information which has been valuable in studying the origin and spread of MRSA.