Trafficking of methicillin-resistant staphylococci and co-colonization with vancomycin-resistant enterococci.

OBJECTIVES To determine the trafficking of methicillin-resistant staphylococci between the hospital and community as well as the occurrence of co-colonization with vancomycin-resistant enterococci (VRE). SUBJECTS AND METHODS From November 2005 to April 2006, methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus (MRCoNS)-positive patients at the Salmaniya Medical Complex, Bahrain were assessed for VRE co-colonization. Characterization of vancomycin resistance genotype by PCR was carried out. Close family contacts were screened for MRSA and pulsed-field gel electrophoresis (PFGE) analysis of MRSA isolates from patient-family member pairs was conducted. RESULTS One hundred and eighty-two patients (93 MRSA; 89 MRCoNS) and 356 family members were enrolled. Seven MRSA and 41 MRCoNS strains were isolated from the family members. PFGE analysis revealed the presence of variants of a single MRSA clone among patients and their relatives. A total of 112 patients (62 MRSA; 50 MRCoNS) provided stool for VRE screening. Of these 13 stool specimens (11.6%) were VRE-positive. All the VRE isolates were from MRSA-positive patients, thus positivity rate among MRSA patients was 20.9% (n/N = 13/62). These were predominantly Enterococcus gallinarum with vanC1 genotype and one strain was Enterococcus faecium (vanB genotype). Two E. gallinarum isolates harbored an additional vanB gene. The majority of VRE isolates were from patients in medical and surgical units (n/N = 10/13; 77%). Male gender, prolonged hospitalization and presence of co-morbidities were significantly associated with MRSA/VRE co-colonization (p < 0.05). CONCLUSION MRSA/VRE co-colonization with MRSA trafficking between the hospital and community environment is a public health concern occurring in our setting.