Relatedness of MRSA and VRE Strains Isolated from Post-acute Care Patients and Their Environment: a Longitudinal Assessment

BACKGROUND: Methicillin-resistant S. aureus (MRSA) and Vancomycin-resistant enterococci (VRE) are endemic in post-acute care (PAC) settings. We characterize their transmission between patients and environment in 6 PAC facilities in SE Michigan. METHODS: In a multicenter prospective observational cohort study we collected surveillance cultures of nares, oropharynx, groin, perianal area, wounds, device site(s) and 10 environmental sites collected at enrollment, day 14, and every 30 days thereafter from 651 newly admitted patients. Pulsed-field gel electrophoresis (PFGE) and PCR for SCCmec, agr, and Panton–Valentine leukocidin (pvl) were performed for MRSA. PFGE, and vanA/vanB genotyping were performed for VRE. RESULTS: 386/651 (59%) participants were not colonized with MRSA at baseline, had more than 1 follow-up visit and were observed for 15,683 patient-days, over which 5,558 patient and 11,108 environmental swabs were collected. Of these 386 patients, 47 (12%) newly acquired MRSA and had complete strain typing available. 42% of strains were USA 100 HA-MRSA, and 31% were USA 300 CA-MRSA. 14% of strains were non USA 100–1100 strains. For 11/47 (23%), a related MRSA strain was isolated from the environment during the previous visit (Figure 1). 24/47 had a subsequent follow-up visit. In 13/24 (54%) a related MRSA strain was found in the environment on the next visit, suggesting transmission from the patient to the environment (Figure 1). For VRE, PFGE profiles showed high heterogeneity. Among 76 of 296 patients (followed for 11,580 days) who newly acquired VRE, a related VRE was found in the previous visit in 12% of patients, no VRE was found in the previous visit for 42 (55%), and an unrelated strain was present for 33%. In 37 patients for whom a follow-up visit was available, 22% had a related VRE strain in the environment on the subsequent visit and 27% had a new VRE strain. CONCLUSION: New acquisition of VRE was more common than MRSA in this PAC population. Using molecular epidemiologic methods in this large prospective cohort, we show active, frequent and immediate bi-directional transmission between patients and environment. Diminishing environmental contamination has the potential to reduce MDRO transmission to patients in a setting where MRSA and VRE are endemic. DISCLOSURES: M. Cassone, National Institute on Aging: Grant Investigator, Research grant; Centers for Disease Control and Prevention: Investigator, Research support; C. Armbruster, Centers for Disease Control and Prevention: Investigator, Research support; E. S. Snitkin, Centers for Disease Control and Prevention: Investigator, Research support; K. Gibson, National Institute on Aging: Investigator, Research grant; Centers for Disease Control and Prevention: Investigator, Research support J. Mantey, National Institute on Aging: Investigator, Research grant; Centers for Disease Control and Prevention: Investigator, Research support; K. C. Reyes, Centers for Disease Control and Prevention: Investigator, Research support S. Altamimi, Centers for Disease Control and Prevention: Investigator, Research support; M. B. Perri, Centers for Disease Control and Prevention: Investigator, Research support; M. J. Zervos, Centers for Disease Control and Prevention: Investigator, Research support; L. Mody, National Institute on Aging: Grant Investigator, Research grant; Centers for Disease Control and Prevention: Investigator, Research support