An Evaluation of Microbial Contamination in Ontario Beach Waters: qPCR Vercus Culture for Enterococcus

Abstract

Contamination in recreational beach water is currently assessed using culture-based measurements of fecal indicator bacteria, a process that requires eighteen to twenty-four hours, from the time of sample collection until results can be released (Converse 2012). Due to the fluctuating nature of microbial contamination, data obtained twenty-four hours later are barely pertinent, and decisions regarding beach closure must be made on outdated information. To avoid this lag, real time polymerase chain reaction (qPCR) has been suggested as an alternate testing method, since it directly measures the genetic material in a sample, and thus can reduce lag time to about three to four hours (Ferretti 2010). The major concern of using qPCR is that the value obtained is a measure of DNA in a sample, and, even though the value can be compared to the amount of DNA in one cell, there may be DNA in the sample that should not be counted towards the total, such as DNA from dead organisms (Haugland 2005). This paper focuses on samples collected during the summer of 2012 from Outlet Beach and Bath Filtration Plant in Kingston, Ontario. DNA was extracted from the samples and subjected to qPCR. The amount of DNA was then compared to a known amount of DNA in calibrator cells. This calculated calibrator cell equivalent value can then be compared to the colony forming unit value, as determined by membrane filtration. Through statistical analysis, a relationship can then be found between the two related values.