Emergence of community-associated MRSA (CA-MRSA) in Northern Ireland

In the summer of 2006, a previously healthy 16 year old individual presented to the local Accident and Emergency Department, of a Northern Ireland hospital, with a 1.5cm diameter abscess over the left great toe, surrounded by cellulitis. The lesion had failed to respond to oral flucloxacillin prescribed by the family doctor. Apart from trauma to the toe three weeks previously, the patient had no significant past medical history and no risk factors for the acquisition of meticillin-resistant Staphylococcus aureus (MRSA). The lesion required incision and drainage on two occasions. Culture of pus revealed MRSA and treatment was changed to oral doxycyline. Phenotypically, the organism behaved unusually, in that it was sensitive to ciprofloxacin, unlike the majority of other MRSA isolates seen. Detailed molecular work-up of the isolate demonstrated that it carried the Panton Valentine Leukocidin (PVL) gene locus and belonged to subclass IV of the Staphylococcal Chromosomal Cassette (SCCmec), a typical microbiological characteristic of community-associated MRSA (CA-MRSA). To date, there has been an extensive awareness of MRSA within healthcare facilities, particularly hospitals. More recently, there has been increased reporting of MRSA occurring in the community amongst healthy individuals who have no hospital association. 1 Most recently, the first nosocomial outbreak of community-associated MRSA, has been described in the West Midlands. 2 Eight cases of Panton-Valentine Leukocidin (PVL) positive community-associated MRSA (CA-MRSA) were identified among individuals in a hospital and their close household contacts, of whom four individuals developed an infection, which was fatal in two cases. Transmission of the CA-MRSA strain appeared to have occurred on two separate wards and went undetected until a fatal case was examined in detail. These organisms are termed CA-MRSA (community-associated MRSA) and differ significantly from healthcare-associated MRSA (HA-MRSA). Although all are Staphylococcus aureus, they have distinct epidemiological and microbiological characteristics which are summarised in Tables I and II. Notably CA-MRSA are more likely to produce PVL, a cytotoxin that causes leucocyte destruction and tissue necrosis, than HA-MRSA. Community-associated MRSA has recently emerged in the US as a clinically significant and virulent pathogen. It is associated with serious skin and soft tissue infections, particularly in young healthy individuals in the community and those who have no risk factors for acquisition of HA-MRSA. 1 Several reports have described this organism in individuals in prisons, military personnel, athletes (especially those involved in combat and ball sports, including rugby, American football, wrestling, fencing), male homosexuals and ethnic …