Quantification of bacterial indicators and zoonotic pathogens in dairy wastewater ponds

Abstract

Zoonotic pathogens in land-applied dairy wastewaters are a potential health risk. The occurrence and abundance of 10 pathogens and 3 fecal indicators were determined by quantitative real-time PCR (qPCR) in samples from 30 dairy wastewaters from southern Idaho. Samples tested positive for Campylobacter jejuni, stx(1)- and eaeA-positive Escherichia coli, Listeria monocytogenes, Mycobacterium avium subsp. paratuberculosis, and Salmonella enterica, with mean recoveries of genomic DNA corresponding to 10(2) to 10(4) cells ml(-1) wastewater. The most predominant organisms were C. jejuni and M. avium, being detected in samples from up to 21 and 29 of 30 wastewater ponds, respectively. The qPCR detection limits for the putative pathogens in the wastewaters ranged from 16 cells ml(-1) for M. avium to 1,689 oocysts ml(-1) for Cryptosporidium. Cryptosporidium and Giardia spp., Yersinia pseudotuberculosis, and pathogenic Leptospira spp. were not detected by qPCR.

Fig 1

Comparison of culture-dependent and qPCR estimates of numbers of enterococci, E. coli, and C. perfringens in the dairy wastewaters from (A) June, (B) August, and (C) October. Quantitative PCR was based on positive amplification of target genes using EC, Eco, and cpa primers for enterococci, E. coli, and C. perfringens, respectively. Columns represent means ± standard deviations (n = 30). Columns with different letters (a or b) indicate a significant difference between the two quantification techniques (P < 0.05).