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  • Detection of Salmonella enterica and Listeria monocytogenes in alternative irrigation water by culture and qPCR-based methods in the Mid-Atlantic U.S.
Title: Detection of Salmonella enterica and Listeria monocytogenes in alternative irrigation water by culture and qPCR-based methods in the Mid-Atlantic U.S.
ABSTRACT Alternative irrigation waters (rivers, ponds, and reclaimed water) can harbor bacterial foodborne pathogens likeSalmonella entericaandListeria monocytogenes, potentially contaminating fruit and vegetable commodities. Detecting foodborne pathogens using qPCR-based methods may accelerate testing methods and procedures compared to culture-based methods. This study compared detectionof S. enterica and L. monocytogenesby qPCR (real-time PCR) and culture methods in irrigation waters to determine the influence of water type (river, pond, and reclaimed water), season (winter, spring, summer, and fall), or volume (0.1, 1, and 10 L) on sensitivity, accuracy, specificity, and positive (PPV), and negative (NPV) predictive values of these methods. Water samples were collected by filtration through modified Moore swabs (MMS) over a 2-year period at 11 sites in the Mid-Atlantic U.S. on a bi-weekly or monthly schedule. For qPCR, bacterial DNA from culture-enriched samples (n= 1,990) was analyzed by multiplex qPCR specific forS. entericaandL. monocytogenes. For culture detection, enriched samples were selectively enriched, isolated, and PCR confirmed. PPVs for qPCR detection ofS. entericaandL. monocytogeneswere 68% and 67%, respectively. The NPV were 87% (S. enterica) and 85% (L. monocytogenes). Higher levels of qPCR/culture agreement were observed in spring and summer compared to fall and winter forS. enterica; forL. monocytogenes, lower levels of agreement were observed in winter compared to spring, summer, and fall. Reclaimed and pond water supported higher levels of qPCR/culture agreement compared to river water for bothS. entericaandL. monocytogenes, indicating that water type may influence the agreement of these results. IMPORTANCEDetecting foodborne pathogens in irrigation water can inform interventions and management strategies to reduce risk of contamination and illness associated with fresh and fresh-cut fruits and vegetables. The use of non-culture methods like qPCR has the potential to accelerate the testing process. Results indicated that pond and reclaimed water showed higher levels of agreement between culture and qPCR methods than river water, perhaps due to specific physiochemical characteristics of the water. These findings also show that season and sample volume affect the agreement of qPCR and culture results. Overall, qPCR methods could be more confidently utilized to determine the absence ofSalmonella entericaandListeria monocytogenesin irrigation water samples examined in this study.  more » « less
Award ID(s):
1828910
PAR ID:
10525590
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Editor(s):
Wang, Luxin
Publisher / Repository:
https://pubmed.ncbi.nlm.nih.gov/38376152/
Date Published:
Journal Name:
Microbiology Spectrum
Volume:
12
Issue:
4
ISSN:
2165-0497
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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