Highly epidemic strains of methicillin-resistant Staphylococcus aureus not distinguished by capsule formation,...

In order to investigate whether highly epidemic methicillin-resistant Staphylococcus aureus (EMRSA) strains possess special properties that favour their dissemination and survival, a study was undertaken that examined methicillin-sensitive and methicillin-resistant strains of Staphylococcus aureus isolated in the UK. Included in the study were EMRSA types 1, 2, 3, 15 and 16. Phage types EMRSA-15 and -16, in particular, have emerged as significant hospital pathogens in the UK, resisting standard methods of control and spreading widely, while the incidence of other epidemic types has either declined or not changed. All of the strains included in the study were examined for capsule formation, the amount of bound protein A produced, and quantitative adherence to the human continuous epithelial cell line HEp-2. Although all of these properties varied amongst the strains examined, there was no relationship between any of them and methicillin resistance or epidemic type and, incidentally, no relationship between cell wall-bound protein A content and adherence.