Molecular epidemiology of community- and health care-associated methicillin-resistant Staphylococcus aureus in Manitoba, Canada.

Recently, acquisition of methicillin-resistant Staphylococcus aureus (MRSA) has been increasingly seen in community settings. Beginning in 1995, we have routinely conducted pulsed-field gel electrophoresis (PFGE) of MRSA isolates received at Cadham Provincial Laboratory (CPL) in Manitoba, Canada. Our diverse collection of isolates coupled with molecular subtype information allowed us to assess the extent to which MRSA isolates in general were associated with community acquisition and whether specific PFGE types were more likely to be found in community settings. Forty percent of the MRSA isolates in our analysis were designated community associated (CA), with two of the six most common PFGE types showing a greater likelihood to be CA-MRSA. Overall, CA-MRSA were more likely to show multiple sensitivity to antibiotics and to be associated with younger age groups. Mapping of specific CA-MRSA types over successive 5-year periods showed rapid temporal shifts in prevalence in different parts of the province.