Characterization and rapid control of a vancomycin-resistant Enterococcus faecium (VREF) outbreak in a renal transplant unit in Spain: The environment matters

Abstract

Objective: To describe a clonal outbreak due to vancomycin-resistant Enterococcus faecium (VREF) in the nephrology and renal transplant unit of a tertiary teaching hospital in Barcelona, Spain, and to highlight how active patient and environment surveillance cultures, as well as prompt and directed intervention strategies, mainly environmental, helped to successfully bring it under control.

Patients and methods: A study was conducted on patients admitted to the nephrology ward with any culture positive for VREF over a 6-month period (August 2012-January 2013). Based on the identification of a clonal link between the isolates, weekly rectal screening using swabs was implemented for all patients, as well as environmental cultures and cleaning of medical equipment and the ward. VREF isolates were identified by MicroScan and confirmed by Etest. Bacterial identification was confirmed by MALDI-TOF MS. The presence of van genes, and esp and hyl virulence genes was determined using PCR. The clonal relationship between the isolates was studied first with DiversiLab (bioMérieux), and then by PFGE-Smal and MLST. A two-tier sequence of infection control measures was implemented.

Results: During the study period, VREF was isolated from 13 patients. All cases were colonized with no criteria for infection. VREF isolates were also extensively recovered from the environment and medical equipment. Isolates carried the vanA gene, and were multidrug-resistant, including high-level resistance (MIC >16mg/L) to vancomycin and teicoplanin. Molecular analysis showed that all VREF isolates belonged to sequence type 17 (ST17) carrying hyl virulence genes. After implementing infection control measures in a two-tier sequence, and reinforcing particularly environmental and medical equipment cleaning, no further cases were detected in the follow-up year.

Conclusion: A clonal outbreak of VREF-ST17 involving only colonization is reported. The prompt implementation of aggressive infection control measures in patients and the environment was effective in controlling the outbreak and avoided the potential emergence of infection among patients.

Keywords: Brote; Control de infección; Enterococcus faecium; Infection control; Nosocomial; Outbreak; Renal transplantation; Trasplante renal; VREF.