ATP bioluminescence assay for evaluating cleaning practices in operating theatres: applicability and limitations

Environmental cleaning practice plays an important role in reducing microbial contamination in hospital surfaces and contributes to prevent Healthcare Associated Infections. Adenosine Triphosphate (ATP) bioluminescence assay is a commonly used method for assessing environmental cleanliness on healthcare surfaces. This study tested the feasibility of using ATP-bioluminescence assay for evaluating the efficiency of cleaning procedures in the operating theatre settings, comparing the ATP-bioluminescence test with the traditional culture method. METHODS: The surfaces of 10 operating rooms of two public hospitals (140 samples in total) were examined "at rest", in two moments of the same daily session: before the first scheduled operation (Pre), and before the second, after a clean environment was re-established (Post). Surface contamination was assessed using the cultural method to detect Total Viable Counts (TVC36°C) and ATP-bioluminescence assay (RLU). RESULTS: The examined surfaces presented very low TVCs (geometric means: 1.8 CFU/plate; IC95%: 1.6-2.0), always compliant with the relative reference standards. No statistical correlation was found between ATP values and TVCs. However, considering the results in terms of general evaluation of hygienic quality of surfaces, the two methods were consistent in identifying the most contaminated areas (Hospital A > Hospital B; Pre > Post; most contaminated surfaces: scialytic lamp). Furthermore, the ATP mean values showed a progressive increase from surfaces with TVC = 0 to surfaces with TVC > 15 CFU/plate. CONCLUSIONS: Although not an alternative to cultural methods, the ATP-bioluminescence-assay can be a useful tool to measure the efficiency of cleaning procedures also in environments with very low microbial counts. Each health facility should identify appropriate reference values, depending on the devices used and on the basis of the analysis of the data collected through spatial and temporal sampling series. By providing a rapid feedback, the ATP-assay helps to increase the awareness of operators and allows immediate action to be taken in critical situations.