Rapid dead-end ultrafiltration concentration and biosensor detection of enterococci from beach waters of Southern California

Same-day microbial water quality assessments are not possible with standard methods, which increases the possibility of public exposure to fecal pathogens. This study examined the efficacy of high-volume hollow fibre ultrafiltration coupled to biosensor detection for enterococci in marine waters to allow same-day public notification of poor water quality. Fifty-six 1001 ultrafiltered samples and 100 ml grab samples were collected weekly from May to July 2007. Post-ultrafiltration processing included sonication and micron sieve passage to remove interfering particulates, followed by centrifugation for secondary concentration. Levels of enterococci in grab and ultrafiltration samples were determined by a standard method (EPA method 1600) for calculation of recovery efficiencies and concentration factors. Each final retentate was analysed with the RAPTOR evanescent wave biosensor. Enterococci levels increased over 26,000-fold in final retentates. Enterococci were detected when ambient concentrations exceeded the regulatory standard for a single sample (> or = 105 CFU/100 ml), and detection was highly correlated with breaches of the single-sample regulatory limit. The combined procedure required 2.5 h for detection compared with 24h for EPA method 1600. This field study achieved rapid detection of enterococci by ultrafiltration, secondary concentration and biosensor analysis, and demonstrates its potential usefulness for water quality monitoring.