Microbiological contamination of the inner surface of finished water filling taps at bottled drinking water producers in Khanh Hoa province

The finished water filling tap is the final contact point of filtered drinking water before bottling. Therefore, microbial contamination at this site may result in cross-contamination into the finished water in the bottle. This study was conducted to evaluate microbiological contamination on the inner surface of the finished water filling tap at the bottled drinking water producers in Khanh Hoa in 2022. A total of 93 swab samples of the inside surface of the tap at 93 producers were subjected to a test for ATP (Adenosine Triphosphate), total plate count (TPC), coliform, Escherichia coli, Pseudomonas aeruginosa, Streptococci feacal, and Clostridia. There were 72/93 (77.4%) samples with ATP values higher than 300 RLU/cm2. The geometric mean of ATP and TPC were 3.1±0.8 log (RLU/cm2) and 3.5±1.2 log (CFU/cm2), respectively. The ATP and TPC were linear correlated, indicating that the surface ATP value inside the finished water filling tap was mainly formed by microorganisms. In addition, 6/93 (6.5%) samples were found to be positive for coliform, including 3 strains of Enterobacter cloacae, 2 strains of Klebsiella pneumoniae and 1 strain of Enterobacter aerogenes. Moreover, 1/93 (1.1%) samples were infected with P. aeruginosa. All 7 strains of these bacteria were biofilm producers under laboratory conditions. Our results demonstrated that the cleaning and decontamination of finished water filling taps were not properly processed, thereby increasing the risk of microbial contamination into finished bottled water.