Long-term metabolic persistence of gram-positive bacteria on health care-relevant plastic
Health care-associated opportunistic pathogens Staphylococcus aureus and Enterococcus faecium persist on dry environments and can contribute to organism transmission through contact. These organisms can be monitored on surfaces by culture, molecular methods, or metabolic assays. This study was designed to determine the kinetics of bacterial persistence on acrylonitrile butadiene styrene, a plastic commonly used in the manufacture of bedrails.Materials and methods:
Polymerase chain reaction for genomic DNA was used to confirm the presence of bacteria cells on this plastic irrespective of viability. Bacterial viability was measured by culture, ATP quantification, and a metabolic assay at time points up to and longer than 1 year.Results:
Polymerase chain reaction confirmed the presence of bacteria on the plastic for the entire time period studied. However, S aureus culturability was reduced after 3 and 7 weeks; neither organism was culturable after 1 year. At 7 weeks, ATP levels were reduced for both organisms, paralleling S aureus culturability but indicating that ATP quantification did not predict E faecium culturability. S aureus-reducing potential was reduced after 7 weeks, whereas E faecium-reducing potential reached the level of fresh inoculum after 12 hours in broth culture. Low but significant levels of metabolic activity were detected for each organism after 1 year.Conclusions:
S aureus and E faecium cells may retain viability on plastic for longer than 1 year.