Evaluation of the Effectiveness of Five Sanitizers Using a Surface ATP Test System and Plate Counts

Introduction:  The bioluminescence measured by an ATP hygiene test system is dependent on the quantity of organic matter present on a surface. Lysed cells resulting from the action of sanitizers or the chemical composition of these compounds may influence the levels of Relative Light Units (RLU) measured by an ATP test system, giving false-positive RLU counts.

Purpose:  The aim of this study was to evaluate the effectiveness of five commonly used sanitizers using 3M™ Clean-Trace™ Surface ATP Test System and plate counts.

Methods: Polyethylene plates (n=3) of 32 x 23 cm were divided in 8 squares (6 x 10cm²) and were artificially contaminated with ~10⁴ CFU/ml of Listeria monocytogenes, using a sterile sponge.  Four squares of each plate were swabbed by 3M™ Swab-Sampler and four squares of each plate were swabbed with 3M Clean-Trace Surface ATP swabs, respectively. Samples were taken from control plates (untreated and uncontaminated) and from plates before and after the disinfection by sodium hypochlorite (1% and 2%), biguanide (0.6% and 1.2%), ethylic alcohol (70% and 96 °GL), quaternary ammonium (2% and 4%) and peracetic acid (1% and 2%). Data were statistically analyzed using Wilcoxon, Mann-Whitney and T-test, using Minitab^® software.

Results:   Results indicated that ~10³ CFU/cm² of Listeria monocytogenesadhered to polyethylene plates, but no bacteria were found after disinfection with all sanitizers. The RLU counts of contaminated surfaces were ~3,000 RLU and were reduced to approximately 35-127 RLU after disinfection with all sanitizers. RLU counts verified after all sanitizers were considered statistically similar.

Significance:  RLU counts were slightly higher than RLU counts verified on the controls, indicating the necessity of proper washing after the use of sanitizers and before RLU measures.