title: Microbial quality of agricultural water in Central Florida.
abstract: The microbial quality of water that comes into the edible portion of produce is believed to directly relate to the safety of produce, and metrics describing indicator organisms are commonly used to ensure safety. The US FDA Produce Safety Rule (PSR) sets very specific microbiological water quality metrics for agricultural water that contacts the harvestable portion of produce. Validation of these metrics for agricultural water is essential for produce safety. Water samples (500 mL) from six agricultural ponds were collected during the 2012/2013 and 2013/2014 growing seasons (46 and 44 samples respectively, 540 from all ponds). Microbial indicator populations (total coliforms, generic Escherichia coli, and enterococci) were enumerated, environmental variables (temperature, pH, conductivity, redox potential, and turbidity) measured, and pathogen presence evaluated by PCR. Salmonella isolates were serotyped and analyzed by pulsed-field gel electrophoresis. Following rain events, coliforms increased up to 4.2 log MPN/100 mL. Populations of coliforms and enterococci ranged from 2 to 8 and 1 to 5 log MPN/100 mL, respectively. Microbial indicators did not correlate with environmental variables, except pH (P<0.0001). The invA gene (Salmonella) was detected in 26/540 (4.8%) samples, in all ponds and growing seasons, and 14 serotypes detected. Six STEC genes were detected in samples: hly (83.3%), fliC (51.8%), eaeA (17.4%), rfbE (17.4%), stx-I (32.6%), stx-II (9.4%). While all ponds met the PSR requirements, at least one virulence gene from Salmonella (invA-4.8%) or STEC (stx-I-32.6%, stx-II-9.4%) was detected in each pond. Water quality for tested agricultural ponds, below recommended standards, did not guarantee the absence of pathogens. Investigating the relationships among physicochemical attributes, environmental factors, indicator microorganisms, and pathogen presence allows researchers to have a greater understanding of contamination risks from agricultural surface waters in the field.
authors.affiliation: Department of Food Science and Human Nutrition, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida, United States of America.
authors.forename: Zeynal
authors.initials: Z
authors.lastname: Topalcengiz
authors.affiliation: Department of Food Science and Technology, Agricultural Research and Extension Center, Virginia Tech, 33446 Research drive, Painter, Virginia, United States of America.
authors.forename: Laura K
authors.initials: LK
authors.lastname: Strawn
authors.affiliation: Department of Food Science and Human Nutrition, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida, United States of America.
authors.forename: Michelle D
authors.identifier: http://orcid.org/0000-0001-5780-7911
authors.initials: MD
authors.lastname: Danyluk
mesh_terms: D000383:Agriculture; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000302:isolation & purification; D005431:Florida; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D011891:Rain; D012475:Salmonella / Q000302:isolation & purification; D013696:Temperature; D014871:Water Microbiology