Extensive contact tracing and screening to control the spread of vancomycin-resistant enterococcus faecium ST414 in Hong Kong

Background Proactive infection control management is crucial in preventing the introduction of multiple drug resistant organisms in the healthcare setting. In Hong Kong, where vancomycin-resistant enterococci (VRE) endemicity is not yet established, contact tracing and screening, together with other infection control measures are essential in limiting intraand inter-hospital transmission. The objective of this study was to illustrate the control measures used to eradicate a VRE outbreak in a hospital network in Hong Kong. Methods We described an outbreak of VRE in a healthcare region in Hong Kong, involving a University affiliated hospital and a convalescent hospital of 1600 and 550 beds respectively. Computer-assisted analysis was utilized to facilitate contact tracing, followed by VRE screening using chromogenic agar. Multi-locus sequence typing (MLST) was performed to assess the clonality of the VRE strains isolated. A case-control study was conducted to identify the risk factors for nosocomial acquisition of VRE. Results Between November 26 and December 17, 2011, 11 patients (1 exogenous case and 10 secondary cases) in two hospitals with VRE colonization were detected during our outbreak investigation and screening for 361 contact patients, resulting in a clinical attack rate of 2.8% (10/361). There were 8 males and 3 females with a median age of 78 years (range, 40-87 years). MLST confirmed sequence type ST414 in all isolates. Case-control analysis demonstrated that VRE positive cases had a significantly longer cumulative length of stay (P <0.001), a higher proportion with chronic cerebral and cardiopulmonary conditions (P=0.001), underlying malignancies (P <0.001), and presence of urinary catheter (P <0.001), wound or ulcer (P <0.001), and a greater proportion of these patients were receiving β-lactam/β-lactamase inhibitors (P=0.009), carbapenem group (P <0.001), fluoroquinolones (P=0.003), or vancomycin (P=0.001) when compared with the controls. Conclusion Extensive contact tracing and screening with a "search-and-confine" strategy was a successful tool for outbreak control in our healthcare region.