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Objective: To Investigate and control a VRE outbreak.
Methods: The setting was a 672-bed public academic hospital with a 72-bed level III neonatal intensive care unit (NICU). The investigation and control efforts began in May 2010, and are currently ongoing. Weekly active screening cultures (ASC) were begun in the NICU after finding the index neonate. Outbreak control measures were initiated, including staff re-education on hand hygiene and isolation precautions, staff and patient cohorting, and increased environmental cleaning. Parents of the neonates were screened for colonization with VRE. To evaluate for clonal relatedness to VRE occurring among adult medical-surgical patients in other wards, strain typing of VRE isolates was done using repetitive element PCR (rep-PCR). Environmental cultures were done. Prevalence of VRE colonization among birth mothers was assessed prospectively over a 3-month period. Review of medical records was performed.
Results: Fifteen neonates were identified with VRE, all of whom were colonized. Majority (8/15) belonged to a single outbreak strain type. Antimicrobial use in the NICU during prior months was not increased. No outbreak was occurring in any other ward at the time. Prompt outbreak control measures led to elimination of VRE in the NICU by July 2010. Of the 56 available VRE isolates identified upon clinical cultures among adult medical-surgical patients during Feb-10 to Sep-10, 20(36%) belonged to the outbreak strain. VRE isolated from a birth mother of a pair of twins colonized with the outbreak strain, and a clean pulse oximeter device shared across medical-surgical floors, also belonged to the outbreak strain type. One additional birth mother was identified with VRE (not the outbreak strain) upon prospective screening of mothers whose neonates were transferred to the NICU; prevalence of 1/265 (0.4%). Comparison of clinical characteristics of 20 adult medical-surgical patients with the outbreak strain (cases) with those of 20 randomly selected adult medical-surgical patients with non-outbreak strain of VRE (controls) showed no differences except higher use of Meropenem within 30 days prior to VRE culture date among cases (Mann-Whitney two-tailed P-value 0.038). Use of Voriconazole (p = 0.076) showed a trend towards higher use among the cases; Ceftriaxone (p = 0.064) showed a trend towards higher use among controls.
Conclusions: An endemic strain of VRE among adult medical-surgical patients was responsible for a subsequently controlled outbreak in the NICU, presumably through shared equipment and colonization of a birth mother. Increase in use of specific antimicrobials may select for specific VRE strains.