Comparative molecular analysis of community or health care associated methicillin-resistant staphylococcus aureus

ABSTRACT

Methicillin-resistant Staphylococcus aureus [MRSA] is no longer only hospital acquired. Community acquisition was defined as growth of the isolates within 48 hours after hospital admission in patients who had no risk factors for nosocomial acquisition, including no hospitalizations or nursing home residence in the year before admission. Community-acquired methicillin-resistant Staphylococcus aureus [CA-MRSA] is a growing public health Concern It is hypothesized that the evolution of CA-MRSA is a recent event due to the acquisition of mec DNA by previously methicillin-susceptible strains that circulated in the community. This study investigated the genetic relatedness between CA-MRSA and hospital-associated MRSA [HAMRSA]. Isolates were typed by resistance pattern, plasmid analysis, pulsed field gel electrophoresis, bacteriophage pattern, coagulase gene restriction fragment length polymorphism and SCC mec. Thirty out of the 32 CA-MRSA isolates were closely related as determined by pulsed field gel electrophoresis and yet were unrelated to the 32 HCA-MRSA strains. All CA-MRSA isolates tested contained a type IV staphylococcal cassette chromosome mec [SCCmec] element. Antibiotic susceptibility patterns showed difference between the CA-MRSA and HA-MRSA isolates; Thirty of the CA-MRSA isolates were typically resistant only to beta-lactam antibiotics. Non of the CA-MRSA were typeable by the international set of phages