Eradication of a Large Outbreak of a Single Strain of vanB Vancomycin-ResistantEnterococcus faeciumat a Major Australian Teaching Hospital

Abstract

Objective:To demonstrate that nosocomial transmission of vancomycin-resistant enterococci (VRE) can be terminated and endemicity prevented despite widespread dissemination of an epidemic strain in a large tertiary-care referral hospital.Interventions:Two months after the index case was detected in the intensive care unit, 68 patients became either infected or colonized with an epidemic strain of vanB vancomycin-resistantEnterococcus faeciumdespite standard infection control procedures. The following additional interventions were then introduced to control the outbreak: (1) formation of a VRE executive group; (2) rapid laboratory identification (30 to 48 hours) using culture and polymerase chain reaction detection ofvanA andvanBresistance genes; (3) mass screening of all hospitalized patients with isolation of carriers and cohorting of contacts; (4) environmental screening and increased cleaning; (5) electronic flagging of medical records of contacts; and (6) antibiotic restrictions (third-generation cephalosporins and vancomycin).Results:A total of 19,658 patient and 24,396 environmental swabs were processed between July and December 2001. One hundred sixty-nine patients in 23 wards were colonized with a single strain of vanB vancomycin-resistantE. faecium.Introducing additional control measures rapidly brought the outbreak under control. Hospital-wide screening found 39 previously unidentified colonized patients, with only 7 more nonsegregat-ed patients being detected in the next 2 months. The outbreak was terminated within 3 months at a cost of $2.7 million (Australian dollars).Conclusion:Despite widespread dissemination of VRE in a large acute care facility, eradication was achievable by a well-resourced, coordinated, multifaceted approach and was in accordance with good clinical governance.

Current Trends of Emergence and Spread of Vancomycin-Resistant Enterococci

“…VanB-type resistance is only highly prevalent in certain parts of the world, for instance, in Australia (Christiansen et al, 2004;Pearman 2006;Worth et al, 2008;Pendle et al, 2008;Johnson et al, 2010) or Singapore Koh et al, 2009) where vanB-type vancomycin resistance among clinical E. faecium is more prevalent than the vanA-type. The reason(s) for this remain unknown and are not linked to a supposed larger reservoir of the vanB cluster in commensal intestinal colonizers (Padiglione et al, 2000), rates of which were similar in Australian, US-American and European studies (Stamper et al, 2007;Graham et al, 2008;Grabsch et al, 2008b;Bourdon et al, 2010;Werner et al, 2011c).…”

“…In general, the supposed low expression of vancomycin resistance among vanB strains may have lead to an underestimation of its general prevalence, since in many screening studies comparably high vancomycin concentrations were used to select VRE (Poole et al, 2005;Hershberger et al, 2005). Rates of clinical vanB-type VRE are increasing, at least in some European countries www.intechopen.com during last years Soderblom et al, 2010;Bourdon et al, 2011) and a link to a supposed reservoir outside the clinical setting, for instance, among mammal intestinal colonizers is discussed also in areas where vanB-type vancomycin resistance is more prevalent (Christiansen et al, 2004;Johnson et al, 2010).…”

“…Acquired resistance to vancomycin is mediated by various mechanisms (types VanA/B/D/E/G/L; Table 1); the vanA and vanB resistance genotypes are by far the most prevalent. The reservoir for vanA-and vanB-type resistance in humans is in E. faecium (Christiansen et al, 2004;Willems and van Schaik W. 2009;Johnson et al, 2010;Willems et al, 2011). Consequently, increasing rates of VRE in several European countries are due to an increasing prevalence of vancomycin-resistant E. faecium (VREfm).…”

Vancomycin-resistant enterococci in hospitals

“…Low rates of polyclonal vanB-VRE carriage have also been detected in various community populations, including residential aged care residents 8,11,12 . No animal reservoir has been identified in recent surveys.…”

“…The comprehensive approach to outbreak investigation and management is well described in other references 35 and well illustrated by the description of the recent WA VRE outbreak 11 . …”