Eight cases of Panton-Valentine leukocidin (PVL) positive community-associated MRSA (CA-MRSA) have been identified among individuals in a hospital and their close household contacts in the West Midlands. Four individuals developed an infection, two of whom died.
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. Although the occurrence of several different clones of CA-MRSA has been reported previously [1], this is the first documented report of nosocomial transmission of PVL-positive CA-MRSA in the United Kingdom (UK).
A previously healthy healthcare worker (HCW) developed an MRSA sepsis, septic shock, pneumonia and died following non-elective surgery in September 2006 (case 1). Screening of patients and staff on ward A where case 1 worked revealed another HCW carrying the same strain (case 2). This HCW had a history of skin abscesses due to MRSA and was a social contact of case 1. Four household contacts of cases 1 and 2 were found to carry the same strain (cases 3 to 6). One of these, case 5, worked as a HCW on a different ward (ward B). Subsequent screening of both patients and staff on ward B revealed another HCW working on ward B carrying the same strain (case 7). This individual had a four month history of recurrent infection of the eye lids. One further case was identified in March 2006 through retrospective analysis of MRSA isolates kept in the laboratory. The patient (case 8) developed a suspected hospital-acquired pneumonia while in ward A and died within 24 hours of the blood culture being taken that grew the organism. Extensive healthcare and community-based contact tracing has not identified further cases.
The most prevalent hospital and healthcare-associated MRSA strains found in UK healthcare settings are epidemic MRSA (EMRSA) 15 and 16, both of which are negative for PVL and usually resistant to ciprofloxacin. The MRSA strain responsible for this outbreak was susceptible to all non-beta-lactam antibiotics tested (including ciprofloxacin), positive for the PVL genes and resembled closely the South West Pacific CA-MRSA clone (multilocus sequence type ST30) [1,2]. Data from the national Staphylococcus Reference Laboratory show this is the fifth most common clone of CA-MRSA seen in England and Wales, with 13 cases of skin and soft tissue infection (SSTI) identified in 2005. This outbreak heralds the first report of nosocomial transmission and known deaths due to this strain in England and Wales.
In recent years CA-MRSA has emerged as an important pathogen among previously healthy young people in community settings worldwide. In addition to causing sporadic disease in the community, outbreaks of CA-MRSA have occurred in individuals in close contact, particularly where skin trauma is likely, for example sporting teams, military recruits and injecting drug users. Many strains of CA-MRSA encode PVL, a poreforming cytotoxin associated with necrotic lesions or abscess formation in SSTI [3]. More rarely, infection can lead to cases of serious, life-threatening disease such as necrotising pneumonia, necrotising fasciitis and purpura fulminans which may prove fatal [3].
A recent review [4] identified 12 reports world-wide documenting nosocomial transmission of various clones of CA-MRSA. This change in the epidemiology of MRSA demands increased vigilance among healthcare personnel. To enhance the case ascertainment of PVL-positive CA-MRSA in the healthcare and community setting, we would encourage the submission of samples from patients presenting with SSTIs (particularly boils, furuncles and abscesses, especially where they are recurrent) for microbiological testing. In conjunction with this, we recommend microbiologists test MRSAs for susceptibility to ciprofloxacin as a marker of putative CA-MRSA since the majority of healthcare-associated MRSA are resistant to ciprofloxacin [1]. All ciprofloxacin sensitive MRSAs, accompanied by relevant clinical information, should be referred to the Staphylococcus Reference Laboratory (Centre for Infections, HPA, 61 Colindale Avenue, London, NW9 5EQ) for characterisation including PVL testing to determine if they are CA-MRSA.