Development and application of real-time PCR assays for quantifying total and aerolysin gene-containing aeromonas in...

Aeromonas spp., opportunistic pathogens, are listed as a microbiological contaminant on the Environmental Protection Agency's (EPA) Drinking Water Contaminant Candidate List. Culture-based methods for identification and quantification of Aeromonas in drinking water are time-consuming and often fail to differentiate pathogenic species from nonpathogenic ones. This study reports successful development and applications of two real-time PCR assays, based on 16S rRNA gene sequences and a virulence gene (aerolysin gene), for rapid and effective quantification of total and aerolysin gene-containing Aeromonas spp. The assays successfully quantified total and aerolysin gene-containing Aeromonas in source, intermediate, and finished water samples collected from seven water works and one pilot plant. The effectiveness of Aeromonas removal by different drinking water treatment processes was examined by comparing the results obtained from the EPA culture-based method and developed real-time PCR assays. Regardless of the methods, our results indicated that conventional water treatment combination (prechlorination/ coagulation/sedimentation/rapid sand filtration) and membrane filtration alone could effectively remove Aeromonas. Slow sand filtration alone might not be effective. The removal efficiencies by different disinfection treatments were not determined, due to the lack of detectable Aeromonas. No Aeromonas was detected in samples with turbidity below 0.06 NTU.