ATP luminescence measurements (using Relative Light Units, RLU) has been used to assess the levels of bacterial contamination on the surfaces of various materials. However, not much is known about their suitability in assessing bacterial contamination on paper surfaces. This study was conducted to evaluate the feasibility of using ATP luminometers in measuring levels of bacteria contamination on paper surfaces. The three ATP luminometers studied were Clean-Q, smart PD-30, and 3M™ Clean-Trace™ LM1 manufactured by different companies. There were some differences in RLU results among the three ATP luminometers when they were tested with different concentrations of Micrococcus luteus cell suspension. 106 - 107 cells were required in order to effectively detect Bacillus subtilis, Escherichia coli, and Micrococcus luteus on the surfaces of A4 printing sheets (100 cm2) when using the three ATP luminometers. The sizes and physical properties of surface areas varied slightly among the swabs used for the three ATP luminometers. Concentration-specific measurements (RLU) of M. luteus taken from the surfaces of six kinds of paper (fine print paper, medium print paper, ground paper, newsprint paper, practice paper, tracing paper) were possible using the smart PD-30 and LM1 ATP luminometers. ATP detection values of M. luteus varied among the six types of paper. The highest ATP detection values were found on the surfaces of tracing paper. If the RLU value is recorded at the level of 1000, this could indicate a very high bacterial contamination level of 105 to 106 CFU/4 cm2.

This study was conducted to obtain basic information for the use of the ATP fluorescence detection method in consideration of the most common and frequent contamination situation that occurs in laboratories dealing with fire blight causing bacterium, Erwinia amylovora. ATP luminescence measurements (Relative Light Unit, RLU) were tested against these pathogen cells (CFU/cm2) which were artificially introduced on the disinfected surface of a bench floor of a biosafety cabinet (Class 2 Type A1), on a part of the disinfected surface of a lab experimental bench, on a part of the disinfected floor, and on a part of the disinfected floor of an acryl chamber for bioaerosol studies in a biosafety laboratory (BSL 2 class) using two different ATP bioluminometers. RLU values were not much increased with the bacterial cells from 2.15 × 102/cm2 to 2.15 × 106/cm2. RLU values varied among the four different surfaces tested. RLU values measured from the same number of bacterial cells differed little between the two different ATP bioluminometers used for this study. RLU values obtained from bacterial cells higher than 2.15 × 107/cm2 indicated the presence of bacterial contamination on the four different surfaces tested. The R2 values obtained based on the correlation data for the RLU values in response to different E. amylovora cell numbers (CFU/ cm2) on the surfaces of the four test spots ranged from 0.9827 to 0.9999.