Controlling bacteriological contamination of environmental surfaces at the biological isolation and containment unit of a veterinary teaching hospital

BACKGROUND: The Biological Isolation and Containment Unit (BICU) is a subunit of the Teaching Hospital of the Faculty of Veterinary Medicine of the University of Lisbon, Portugal, for the admission of animals with confirmed infectious diseases or under clinical suspicion and waiting for a diagnosis. As a high-risk environment for the transmission of infectious agents, it is extremely important to implement programs for the surveillance of nosocomial microorganisms in these facilities. The purpose of this study was to evaluate the level of bacterial contamination of the BICU environmental surfaces and to implement corrective actions on disinfection protocols. Swab samples were collected from selected environmental surfaces in 3 different areas of the BICU (isolation, work, and preparatory rooms) to evaluate the total aerobic bacterial load and investigate the presence of 4 nosocomial microorganisms: vancomycin-resistant Enterococcus spp., methicillin-resistant Staphylococcus aureus, 3rd-generation cephalosporin-resistant Escherichia coli, and carbapenem-resistant Pseudomonas aeruginosa. Bacterial quantification was performed by using non-selective media, while specific selective media were used for the isolation of the target microorganisms. Isolates were identified based on their macro and microscopic characteristics and their biochemical profile. Subsequently, new disinfection protocols were implemented, and their effectiveness evaluated. RESULTS: The surfaces with the highest bacterial load in the isolation, preparatory, and worker’s rooms were the cages, hand-held sponge, and telephone, respectively. Regarding the 4 pathogens investigated, Enterococcus spp. were the most frequently isolated (11.3%), followed by E. coli (1.5%) and P. aeruginosa (1.5%). One of the P. aeruginosa isolates obtained was resistant to imipenem. In the end, new disinfection protocols were implemented, which proved to be effective in reducing bacterial counts by 99.99% in cages and the sponge, and by 90 to 99% on the telephone. CONCLUSIONS: This study allows to conclude that the cages and the human contact surfaces were the most contaminated in the isolation rooms. Nevertheless, the new disinfection strategies seemed to be effective in reducing environmental contamination, including by some potentially nosocomial agents, although more samples must be analyzed for definitive conclusions. These results may contribute to highlight the importance of infection prevention and control measures, as fundamental tools to reduce the spread of infectious agents in the hospital environment.