Underestimating the Levels of Microbiological Contamination on Environmental Surfaces Within NHS Hospitals

Abstract

<h3>Background</h3> Historically, environmental surfaces were thought to have an insignificant role in healthcare-associated infection transmission; and hospital cleaning was merely aesthetic. Nowadays, cleaning is a crucial activity in managing surface bioburden and preventing pathogen acquisition in patients. Equally important is monitoring of surfaces – current guidelines suggest patients are at greater risk when surfaces exceed 5 colony forming units (CFU) per cm2 for total aerobic counts. Standard nutrient-rich media, used for monitoring surfaces, may fail to culture all microbes present; often discounting dormant or difficult to culture organisms. Research efforts are currently underway, across multiple NHS Trusts, to more accurately quantify the base levels of microbial contamination on critical environmental surfaces. <h3>Methods</h3> Surfaces within close-proximity to patients were periodically swabbed, over two years, for microbial bioburden and cultured using non-specific, improved sensitivity culture media. Samples were categorised according to NHS Trust, date of sampling and distance of surface from the patient. Additional, molecular-based techniques including epifluorescence microscopy and genomic sequencing were employed to further evaluate microbes present. <h3>Results</h3> The presented data shows >60% of samples exceeded the levels defined above for microbial contamination (averaging 380000 CFU/cm2). Our media demonstrated improved recovery rates from surfaces – 36% compared with routine media. Despite procedural variations on cleaning, across the sites, microbiological contamination levels were comparable. Significant differences were discovered for distances between surface and patient; an indirect relationship existed between the distance from a patient and microbe recovery rates. Epifluorescence microscopy of culture-negative samples found populations of viable microbes (estimated <h3>Conclusions</h3> The presentation will discuss the implications of underestimating surface contamination and the applicability of current detection methods, and the need for multi-faceted approaches including molecular-based techniques. The abundance of environmental species discovered here have an unknown impact on patient health and raise questions on the adequacy of hospital cleaning.