Characterisation of methicillin-resistant isolates of Staphylococcus aureus by analysis of whole-cell and exported proteins.

Thirty-four isolates of methicillin-resistant Staphylococcus aureus (MRSA) from patients in Glasgow Royal Infirmary were studied. Whole-cell protein profiles obtained by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) were compared with banding patterns produced by immunoblots of exported proteins. Human plasma was used as a source of staphylococcal antibodies for the immunoblots. SDS-PAGE of whole-cell extracts did not usefully distinguish different isolates of MRSA. Reproducible banding patterns were obtained by immunoblots of exported proteins. Analyses of immunoblots by use of the Dice coefficient demonstrated that isolates of MRSA could be divided into two main groups. Immunoblots of exported proteins provided a rapid, reproducible and sensitive method for characterisation of MRSA.