Detection and quantification of microorganisms using a high-volume ultrafiltration concentration method in Hawaii

摘要

It is well accepted that the distribution of microbes in the environment isrnpatchy, yet current water quality monitoring programs still rely on analyses of waterrnsamples that rarely exceed 100 ml. A single 100 ml water sample has a very limitedrnvalue and may not provide adequate representation of microbial water quality andrnassociated human health risk at a given site.rnThis paper evaluates a dead-end hollow fiber based ultrafiltration method that isrncapable of concentrating samples exceeding a 100 L volume. In partnership with thernHawaii Department of Health and City and County of Honolulu, coastal, source andrndrinking water samples were analyzed for total bacteria, total coliforms, Escherichia coli,rnenterococci, Clostridium perfringens spores, F+ RNA coliphages, human polyomavirusesrnand human specific Bacteroides concentrations. Conventional grab samples (1 L) andrnsamples concentrated using the ultrafiltration method (100 L), were collected andrnanalyzed in parallel.rnMicrobial concentration estimates for 100 ml sample volumes derived by thernconventional grab sample were comparable, although in many cases exceeded thosernderived using the ultrafiltration method back calculated for the same sample volume.rnSeveral microorganisms, F+ RNA coliphages and human polymaviruses, eludedrndetection in all the grab samples collected, whereas both groups were detected in 42%rnof the samples analyzed using the ultrafiltration method, indicating the higher sensitivityrnof the later method and the effectiveness of the ultrafiltration method to concentrate 28rnnm sized viral particles.rnIt should be noted that while no grab sample contained significant levels of PCRrninhibitors, coastal samples collected using the ultrafiltration method were compromisedrnby PCR inhibitors after pH adjustment which is required for human polyomavirusrnrecovery. This inference was avoided by using tenfold diluted DNA extracts.rnBy using the ultrafiltration system we were able to estimate concentrations of E. coli inrntwo Honolulu source water samples to be <0.001 MPN per 100 ml indicating excellentrnmicrobial quality of the city’s source water.rnOur analyses indicate that this type ultrafiltration method is highly sensitive for therndetection and relative quantification of a wide array of microbial targets and provides arnmore comprehensive characterization of microbial water quality.