Assessment of the performance of an ATP based rapid bacterial indicator test on potable water samples.

Foulstone, Phoebe (2020) Assessment of the performance of an ATP based rapid bacterial indicator test on potable water samples. Masters thesis, UNSPECIFIED.

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Abstract

Introduction: There is an increasing need for more rapid detection methods for drinking water supplies; especially in developing areas. Hygiena International Ltd are a research and development company which have developed an ATP based technology called the MicroSnap (MS) system. MS is currently used in the food industries for the enumeration of bacteria in food samples. The purpose of this study was to determine whether this system could be applicable to the drinking water sector, by investigating the sensitivity and specificity of the product. Methods and Results: There are four MicroSnap devices, MS Total count, Enterobacteriaceae (EB), Coliform, and E. coli. All four systems were analysed using pure bacterial cultures, as positive and negative control strains, to determine if the systems produced accurate and consistent results. Throughout initial testing, MS E. coli consistently produced relative light units (RLU) which were an underestimation of the bacterial load in the presented samples. These results formed the hypothesis that the lytic agent (extractant) in the detection devices was only allowing for a low percentage of bacterial cell lysis. The poor cell lysis meant that the detectable biomarker; β-Glucuronidase, was unlikely to be freed from cells in high enough numbers to be correctly quantifiable by the MS E. coli detection system. Therefore, the original extractant was compared to one altered by Hygiena using plate count methods, and within the MS system. The results gained through these tests showed that the new extractant increased the percentage of cell lysis occurring and thus when analysed within the system, produced higher RLU results. Conclusion: MS E. coli demonstrated that it is not yet applicable in the water sector as the WHO guidelines state that detection method must detect down to 1 CFU per 100ml of water. This investigation found that the lower detection limit for the MS system was around 101 and 102 CFU per ml of water. In order to increase the sensitivity two alterations to the system have been proposed to Hygiena International Ltd. With these suggestions, the system could reduce the current time taken to detect bacteria using traditional methods, down to 7 hours.