Enteroviruses detected by reverse transcriptase polymerase chain reaction from the coastal waters of Santa Monica Bay, California: low correlation to bacterial indicator levels

Abstract

Microbiological water quality at beaches is typically measured only by indicator bacteria, even though viruses are also a concern, because classical culture-based virus assays are not suitable. In this study, molecular-based assays for the detection of enteroviruses by reverse transcriptase polymerase chain reaction (RT-PCR) were performed on 50 coastal seawater samples taken from Santa Monica Bay, CA, over a six-year period, and compared with indicator bacteria. Sample sites were near freshwater outlets in the Bay and popular sandy beaches. RT-PCR is a primer-based molecular biology technique, used to detect the genomes of specific groups or types of viruses based upon conserved sequences. Results of the 50 analyses showed our ultrafiltration concentration methods and RT-PCR protocol could be used consistently to detect enteroviruses from 20 I samples of coastal seawater. Of the 50 samples, 16 (32%) were positive for enteroviruses, 27 (54%) were negative and 7 (14%) were inconclusive. There was no significant correlation between the presence of enteroviruses and individual standard microbiological indicators of fecal contamination, specifically total coliforms, fecal coliforms, or enterococci (r=0.14, r=0.28 and r=0.34, respectively, p>0.05). However, there was a significant correlation (r=0.7l) to a combined set of bacterial water quality standards, involving all three indicators, recently adopted in California. There was no significant correlation between the RT-PCR results and levels of rainfall (a large source of runoff), but our analyses demonstrated that positive results for enteroviruses were significantly more likely during the winter 'wet' season than during the summer 'dry' season. Our results demonstrate that RT-PCR is an effective method for the detection of enteroviruses in coastal seawater, and they suggest that bacterial indicators are not necessarily good predictors of the presence of such viruses. Enteroviruses are known to be important etiological agents of disease from recreational water contact, so analysis for their presence might be advisable at certain locations (e.g. high-use sandy beaches) or during certain seasons of the year.