Staff carriage of epidemic methicillin-resistant Staphylococcus aureus

Twenty-six nurses were repeatedly screened for carriage of epidemic methicillin-resistant Staphylococcus aureus (EMRSA) immediately before and after duty periods in which they solely attended six patients widely colonized with two EMRSA strains distinguishable by plasmid analysis. EMRSA carriage was detected in 13 nurses. Three EMRSA carriage patterns emerged: transient carriage in 12 nurses, when the EMRSA was isolated from noses or fingers of nurses after duty but was gone before their next day's duty; short-term nasal carriage, seen on occasion in 4 of these 12 nurses, when EMRSA carriage was detected on two consecutive screens; and persistent nasal carriage, seen in 1 nurse only, when the EMRSA was seen on more than two consecutive occasions. All but one of these incidents of carriage could be explained by close patient, rather than environmental, exposure and occurred despite an intensive control programme. Transient or short-term carriage in nurses probably resulted in transfer of the EMRSA between patients. Staff decontamination should be considered following a period of cohort nursing of EMRSA patients, especially if staff members are shortly to nurse unaffected patients. Our findings may explain some of the difficulties in controlling EMRSA.