Microbial ecology and antibiotic resistance of microorganisms in intensive care unit environments.

In the UK alone over 320,000 patients per annum acquire at least one nosocomial infection and one in four intensive care unit (ICU) patients worldwide acquire an infection during their hospital stay. Frequently the organisms that cause these infections are opportunistic and resistant to antibiotics. The costs to the NHS are six times higher if ICU patients acquire a nosocomial infection and the mortality rates are greater (30-60 % dependent on the infection).This study investigated the ICU environment for bacterial reservoirs, fungal reservoirs and antibiotic resistance determinants. It was hoped that information about the microorganisms and antibiotic resistance determinants within the ICU may be useful in optimising infection control within the hospital. Samples were taken and analysed via PCR for the presence of bacterial 16S rRNA genes, antibiotic resistance determinants (including mecA and tef) and beta-lactamase genes. Parallel cultural analysis was used to assess the presence of fungi. Bacterial species, diversity and communities were identified using PCR-denaturing gradient gel electrophoresis (PCR-DGGE).Using culture dependent and independent techniques, sequences similar to opportunistic pathogens were retrieved from a variety of ICU environmental sites (patient chair, floor and ward sink plughole). Clinically significant non-albicans Candida species were detected in the hospital environment where individual ICU patients were colonised, suggesting there is a reservoir in the ward environment. Despite the low detection frequency, resistance determinants of clinical relevance (mecA and bla TEM genes) were observed in the ICU environment at sites that may have infection control significance.Several sites used by hospital staff and patients (ward sink plughole, floor, patient chair, sluice room sink plughole, handwash bottles and curtains) within the ICU environment were shown to act as reservoirs for particular fungal (isolates of Candida parapsilosis, Candida tropicalis, Candida glabrata, Candida guillermondii) and bacterial (Burkholderia spp., Stenotrophomonas maltophilia, Acinetobacter spp. and isolates of Micrococcus spp., coaglulase negative Staphylococci) opportunistic pathogens. Routine ICU ward cleaning was largely effective on hard surfaces (floors and patient chairs). Opportunistic pathogens (Stenotrophomonas maltophilia, Burkholderia spp.) could be retrieved via PCR-DGGE after cleaning from ICU ward sink plugholes. There was a wide distribution of bla TEM genes in the ICU environment and detection in clinical isolates is of significance. The results of this study indicate that changes in routine ICU ward cleaning of ward sink plugholes may be beneficial in removing opportunistic pathogens and antibiotic resistance determinants from within these sites.