Who's carrying MRSA? Prevalence of MRSA amongst staff at a district general hospital and associated risk factors

Abstract number: 1733_820

Clark J., Archibald J., Kearns A., Barnass S., Kyi M.

Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) infections are important nosocomial infections in the UK. In efforts to reduce infection rates, interest has focussed on patient colonisation and transmission. The aim of this study was to determine the rate of and risk factors for staff carriage of MRSA in a district general hospital setting.

Methods: Staff who enrolled gave written signed consent. They were required to complete an anonymous questionnaire and a nasal swab was taken for MRSA culture (also anonymous, but linked to the questionnaire). MRSA was identified using standard laboratory methods, and tested for antimicrobial susceptibility using the British Society for Antimicrobial Chemotherapy method. Phage typing and pulsed field gel electrophoresis (PFGE) was conducted at the Centre for Infections, Colindale, London. Statistical analysis was done using Fisher's Exact Test. Approval for the study was granted by the Local Research Ethics Committee.

Results: Of 120 members of staff (21 medical staff, 54 nursing staff, 11 healthcare assistants, 15 student nurses, 19 non-clinical staff) who took part in the study, 10 (8.33%) were found to be carrying MRSA. All the isolates were from nursing staff of varying grades. Previous MRSA carriage was associated with current MRSA colonisation (P value = 0.02), with other symptoms of upper respiratory tract infection (sore throat, runny nose, cough, ``cold'', sneezes, fever and hay fever) showing no statistically significant association. A history of sinusitis or facial surgery, or having been a hospital in-patient in the previous year, were not associated with MRSA colonisation. Typing of the isolates showed most (8/10) were UK EMRSA-15 and the other 2 were EMRSA-16. On PFGE, four isolates were found to be a common pulsotype, EMRSA-15 variant B3, whilst the other 6 were unique to the hospital.

Conclusion: MRSA is an important cause of nosocomial infection and its control is a priority for infection control teams. This study has shown that even when small numbers of staff are screened for nasal carriage of MRSA, carriers are found. Therefore, good infection control practice by staff remains a top priority.