We developed a suitable system of DNA extraction and real-time quantitative polymerase chain reaction (qPCR) for the specific and sensitive quantification of pathogens and other relevant (indicator) organisms in recalcitrant material such as cattle manure. PCR inhibition by coextraction of humic compounds was minimized in this system, resulting in detection sensitivity of one target DNA copy per reaction well. Data from qPCR analysis for Escherichia coli agreed with cultivation based results, but orders of magnitude more fecal enterococci, Enterobacteriaceae and Campylobacter jejuni, were determined by qPCR than by cultivation. These bacteria may have been in a potentially hazardous active but non-cultivable state. The qPCR system is much less time consuming than conventional cultivation, highly specific, can detect non-cultivable organisms, provides high measurement throughput, and is cost attractive. It should be considered as an alternative in various application areas for (prescribed routine) cultivation based assays, e.g. for biosafety and hygiene monitoring.
Current affiliation: Department of Civil and Environmental Engineering, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA