Successful infection control for a vancomycin-intermediate Staphylococcus aureus outbreak in an advanced emergency medical service centre

SummaryBackgroundA vancomycin-intermediate Staphylococcus aureus (VISA) (vancomycin minimum inhibitory concentration: 4 mg/L) outbreak occurred in an advanced emergency medical service centre [hereafter referred to as the intensive care unit (ICU)] between 2013 and 2014.AimOur objective was to evaluate the infection control measures that were successful.MethodsSeventeen VISA strains were isolated from the sputum of 15 inpatients and the skin of two inpatients. Fourteen VISA strains were recognized as colonization. However, three VISA strains were isolated from the sputum of three inpatients with pneumonia. Environmental cultures were performed and VISA strains were detected in five of 65 sites. Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) was performed on 21 VISA strains.FindingsMolecular typing including PFGE and MLST showed that the patterns of 19 VISA strains were identical and those of the other two VISA strains were possibly related. This meant that a horizontal transmission of VISA strains had occurred in the ICU. In August 2013, the infection control team began interventions. However, new inpatients with VISA strains continued to appear. Therefore, in October 2013, the ICU was partially closed in order to try to prevent further horizontal transmission, and existing inpatients with the VISA strain were isolated. Although new cases quickly dissipated after the partial closure, it took approximately five months to eradicate the VISA outbreak.ConclusionOur data suggest that despite the employment of various other infection control measures, partial closure of the ICU was essential in terminating this VISA outbreak.