A collaborative study including Dr. Asli Aslan, assistant professor of environmental health sciences at the Jiann-Ping Hsu College of Public Health Georgia Southern University, examines the persistence of enteric markers in sewage polluted water. The goal of this study was to investigate the effects of storage temperature and transit time on the persistence of these genetic markers.

The existing criteria for detecting microbial pollution in water have limitations such as poor association of fecal indicator bacteria (FIB) with other AGI causing pathogens and more than 18 h of delays in reporting the results. To overcome these problems, the USEPA has published an alternative culture dependent and rapid method. This method is based on detecting the target gene concentration of bacterial DNA. However, there is a need to understand the persistence of these genes in the environment after leaving the host for estimating public health risk.

The researchers contrasted several DNA extraction methods, compared the persistence in solid matrix (sample concentrated and stored on a filter) to liquid suspension (sample stored in a bottle), and tested mathematical models for detecting the relationship between time (up to 28 days) and FIB persistence as measured by qPCR in sewage spiked river water stored at 4, 27 and 37 ˚C. The results showed that the most to least persistent markers were Enterococci, E. coli and B. thetataiotaomicron respectively. The models predicted that enterococci and E. coli cells from water samples stored at 4 ˚C and attached to a matrix needed >28 days for 90 percent decay, however, 27 days were predicted for 90 percent decrease of B. thetataiotaomicron. The results of this study will improve the efficiency of sample collection and storage from remote areas or low resource settings where storage on ice is not an option or extended time in transit is necessary.

[Photo: Dr. Asli Aslan]