A Point-prevalence Study for MRSA in a German University Hospital to Identify Patients at Risk and to Evaluate an Established Admission Screening Procedure

Due to the enormous increase in the number of MRSA-patients, in July 2004, an extended admission screening protocol was implemented in ICUs and surgical wards at Hannover Medical School. In 2005, a point-prevalence study (also known as a cross-sectional study) was conducted to determine the prevalence of MRSA and Panton-Valentine leukocidin (PVL) among inpatients, to identify patients at risk for MRSA colonization and to evaluate compliance with admission screening. Inpatients were screened by taking cultures from nose, throat and skin lesions. S. aureus isolates were tested for antimicrobial susceptibility and PVL. MRSA was analyzed by staphylococcal protein A (spa) typing. Of 509 inpatients, 145 (28%) were S. aureus carriers. 27 (19%) inpatients were MRSA positive, i.e., the MRSA point-prevalence was 5.3% (95% CI, 3.49; 7.70). spa type t032 was predominant in 67% of the MRSA inpatients. The PVL gene was present in one (0.2%) methicillin-susceptible strain. Comparison with data retrieved from the local hospital MRSA database showed that, the status of 37% of the MRSA had previously remained undetected (10/27). Consequently, MRSA colonization was newly identified in 2.0% (10/509) of the patients. Compliance with admission screening failed in three cases. Nosocomial acquisition was identified in three patients. Four other patients harbouring MRSA were newly identified on wards without routine screening (three neurological, one internal medicine ward). Despite extended admission screening, 37% of all MRSA-positive inpatients were missed. The neurological patients were identified as a further risk group and were included in the admission screening procedure established.