MRSA is no longer a problem confined to hospitals and has emerged as a cause of skin and soft tissue infections (SSTI) in the community. If an MRSA infection occurs in people who have not been recently hospitalised, or had a medical procedure (such as dialysis, surgery, catheters) it is known as community-associated MRSA (CA-MRSA). This pathogen is responsible for up to 80% of SSTIs in the USA and Canada and is becoming increasingly prevalent in other countries.
This type of infection often occurs when people are in close physical proximity and at risk of cuts and abrasions – for example, military recruits, children, men who have sex with men, and prisoners. CA-MRSA infections are usually manifested in the skin in the form of abscesses and boils, and occur in otherwise healthy people. They are also implicated in infective endocarditis and the rare, but often fatal, necrotising pneumonia. In the United States, during the 2006-07 flu season, there was a five-fold increase in paediatric influenza-associated deaths in which Staphylococcus aureus (especially MRSA) was present along with the influenza virus.
Many types of CA-MRSA produce Panton-Valentine leucocidin (PVL), a toxin that is not present in infections associated with HA-MRSA. The prevalence of MRSA in the US community is rising and could reach 25% within the next decade, with rates three times as high in hospitals. CA-MRSA is now increasingly prevalent in countries with little history of healthcare-associated MRSA and it may be very diverse. While the current increase in CA-MRSA in the United States is predominantly the result of one type (USA300), in Denmark 29 different strains of CA-MRSA were recently identified within an area of less than 50 square miles.
In a study in Taiwan, one in eight kindergarten children carried CA-MRSA and a study in children in Texas, USA showed that over nine percent carried MRSA. This was an almost twelve-fold increase in prevalence compared with results from a similar population in 2001.
Case study: Minnesota, January 1999
A 13-year-old girl was brought to hospital with fever and respiratory distress. She was coughing up blood. A chest X-ray revealed fluid in the lungs. The girl was treated with the antibiotics ceftriaxone and nafcillin. Within five hours, her blood pressure dropped, and she was transferred to a pediatric hospital, intubated, and treated with vancomycin and cefotaxime.
Despite intensive medical care, the girl’s health deteriorated, and she died on the seventh hospital day from multiple organ failures and excessive fluid and swelling in the brain. An autopsy and tests revealed that MRSA had destroyed her left lung. The girl had no chronic medical conditions and no recent hospitalizations.
Bad Bugs, No Drugs IDSA 2004
Prevalence of MRSA in the community is rising
Recent CA-MRSA outbreaks
in the UK
At the University Hospital of North Shropshire a CA-MRSA outbreak in 2006 infected 11 patients and staff. Two died – a patient and a nurse.
In the Norfolk & Norwich University Hospital, a CA-MRSA outbreak in 2006 infected six babies, one of whom died.
At the Royal Blackburn Hospital 2007, 6 babies were infected with CA-MRSA which in one case was transmitted from the baby to its parents.