Leung et al. (2013) describe the clinical epidemiology, environmental surveillance and infection control interventions undertaken in a six-year persistence of bla-IMP-4 metallo-beta-lactamase (MBL) producing Enterobacteriaceae within a separately confined hospital burn unit in a tertiary hospital in Sydney, Australia.
MBL positive clinical and environmental isolates were collected from the burn unit, from the first detection of isolates in September 2006 to August 2012. Unit-acquired clinical isolates were included, and patient outcomes analyzed amongst those who acquired clinically significant infections. Environmental isolates were analyzed with regard to relationship to clinical isolates, bacterial species, and persistence despite cleaning efforts.
Thirty clinical isolates detected from 23 patients were identified. Clinically significant infection developed in seven (30 percent) patients – two bacteremias, two central venous catheter tip infections without bacteremia, and three wound infections. All patients survived at 30 days. Seventy-one environmental isolates were confirmed to be MBL-positive, with 85 percent sourced from shower facilities or equipment. MBL organisms persisted at these sites despite both usual hospital cleaning, and following targeted environmental disinfection interventions.
The researchers say that a clear association exists between environmental burn unit contamination by MBLs and subsequent patient colonization. Clinical infection occurred in a small proportion of patients colonized by MBLs, and with generally favorable outcomes. Its persistence in the Burns Unit environment, despite concerted infection control measures, pose concern for ongoing clinical transmission. Their research was published in Antimicrobial Resistance and Infection Control.
Reference: Leung GHY, Gray TJ, Cheong EYL, Haertsch P and Gottlieb T. Persistence of related bla-IMP-4 metallo-beta-lactamase producing Enterobacteriaceae from clinical and environmental specimens within a burns unit in Australia - a six-year retrospective study. Antimicrobial Resistance and Infection Control 2013, 2:35 doi:10.1186/2047-2994-2-35