Content area
Full Text
Vancomycin-resistant enterococci (VRE) are major nosocomial pathogens that have been observed worldwide (1,2). VRE were identified in Canada in 1993 (3), but rates of colonization and infection have remained relatively low for years (4,5). VRE bloodstream infections (BSIs) are of particular concern because they are associated with increased illness, length of hospital stay, healthcare costs, and death (6–8). Furthermore, increased rates of VRE BSI have been reported (8).
Since 1999, the Canadian Nosocomial Infection Surveillance Program (CNISP) has conducted surveillance of VRE BSIs, which includes collection of patient epidemiologic data and laboratory analysis of blood isolates, including multilocus sequence typing (MLST) and antimicrobial drug susceptibility testing (5,9). The MLST scheme for Enterococcus faecium relies on the sequences of 7 essential housekeeping genes (10). However, in recent years, MLST nontypeable strains of E. faecium have emerged that do not harbor the pstS gene (11). These pstS-null sequence types (e.g., sequence type [ST] 1421 and ST1424) are believed to have occurred through multiple inversion events and have been reported to be rapidly spreading in Australia, Denmark, and the United Kingdom (11–13). We report emergence and molecular characterization of a pstS-null sequence type (ST1478) that is rapidly disseminating across acute care hospitals in Canada.
The Study
CNISP is administered by the Public Health Agency of Canada and has conducted prospective surveillance for VRE infection and colonization since 1999 (5,9). CNISP is a partnership between the Centre for Communicable Disease and Infection Control and the National Microbiology Laboratory at the Public Health Agency of Canada and sentinel hospitals that participate as members of the Canadian Hospital Epidemiology Committee, a subcommittee of the Association of Medical Microbiology and Infectious Diseases Canada. Hospitalized patients with enterococcal bacteremia characterized as having vancomycin MICs >8 mg/L were eligible (9). A patient was included more than once if a positive VRE blood isolate was identified >14 days after completion of therapy for a previous infection and believed to be unrelated to previous infection in accordance with best clinical judgement (9). Epidemiologic data were collected and VRE...