Evaluating the environmental microbiota across four National Health Service hospitals within England

Abstract

Hospital surfaces contaminated with microbial soiling such as dry surface biofilms (DSBs) can act as a reservoir for pathogenic microorganisms and inhibit their detection and removal during routine cleaning. Studies have recognised such increases in bioburden can hinder the impact of disinfectants and mask the detection of potential pathogens. Cleanliness within healthcare settings is often determined through routine culture-based analysis, whereby surfaces that exhibit > 2.5 colony forming units (CFU) per cm2 pose a risk to patient health and therefore, any underestimation could have detrimental effects. In this study, we quantified the microbial growth on high-touch surfaces in four hospitals within England over 19 months. This was achieved using environmental swabs to sample a variety of surfaces within close proximity to the patient and plating these onto non-specific low nutrient detection agar. The presence of DSBs were confirmed, on surfaces physically removed from the environment, using real-time imaging through episcopic differential interference contrast microscopy combined with epifluorescence. Approximately two-thirds of surfaces tested exceeded the limit for cleanliness (median: 2230 CFU/cm2) whilst 83% of surfaces imaged with BacLight™ LIVE/DEAD™ staining confirmed traces of biofilm. Despite the differences in infection control methods such as choice of surface disinfectants and cleaning personnel, this was not reflected in the microbial variation observed and resulting risk to patients. This highlights a potential limitation in the effectiveness of the current standards for all hospital cleaning and further development using representative clinical data is required to overcome this limitation.