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. 2013 Dec 18;2(1):35.
doi: 10.1186/2047-2994-2-35.

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

Grace Hy Leung, Timothy J Gray, Elaine Yl Cheong, Peter Haertsch, Thomas Gottlieb  1
Affiliations

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

Grace Hy Leung et al. Antimicrob Resist Infect Control. .

Abstract

Background: To 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 burns unit in a tertiary hospital in Sydney, Australia.

Methods: MBL positive clinical and environmental isolates were collected from the Burns 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.

Results: Thirty clinical isolates detected from 23 patients were identified. Clinically significant infection developed in 7 (30%) patients - 2 bacteremias, 2 central venous catheter tip infections without bacteremia, and 3 wound infections. All patients survived at 30 days. Seventy-one environmental isolates were confirmed to be MBL-positive, with 85% sourced from shower facilities or equipment. MBL organisms persisted at these sites despite both usual hospital cleaning, and following targeted environmental disinfection interventions.

Conclusions: Clear association exists between environmental Burns 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.

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Figures

Figure 1
Figure 1
Flowchart of study selection criteria.
Figure 2
Figure 2
Temporal relationship during the prolonged outbreak comparing A) clinical, B) environmental and C) infection control interventions; section B includes overall number of swabs taken during each quarter. Infection control (IC) interventions were; I. Access of deep drains for cleaning; II. Extensive cleaning of all sinks and drains; III. Introduction of regular environmental surveys; IV. Terminal cleaning of the Burns Unit; PA = denotes patients with known MBL colonization prior to transfer into Burns Unit.
Figure 3
Figure 3
Map of BU plotting MBL environmental isolates, compared against rooms dwelled by MBL positive patients.
See this image and copyright information in PMC

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