Levels of Salmonella enterica and Listeria monocytogenes in alternative irrigation water vary nased on water source on the Eastern Shore of Maryland

Authors: ACHEAMFOUR, CHANELLE - University Of Maryland Eastern Shore (UMES); PARVEEN, SALINA - University Of Maryland Eastern Shore (UMES); HASHEM, FAWZY - University Of Maryland Eastern Shore (UMES); Sharma, Manan; GERDES, MEGAN - University Of Maryland; MAY, ERIC - University Of Maryland Eastern Shore (UMES); ROGERS, KORIANTE - University Of Maryland Eastern Shore (UMES); HAYMAKER, JOSEPH - University Of Maryland Eastern Shore (UMES); DUNCAN, RICO - University Of Maryland Eastern Shore (UMES); FOUST, DEREK - University Of Maryland Eastern Shore (UMES); TABODI, MARYAM - University Of Maryland Eastern Shore (UMES); BRADSHAW, RHODEL - US Department Of Agriculture (USDA); Handy, Eric; East, Cheryl - Roberts; KIM, SEONGYUN - US Department Of Agriculture (USDA); MICALLEF, SHIRLEY - University Of Maryland; CALLAHAN, MARY THERESA - University Of Maryland; ALLARD, SARAH - University Of Maryland; ANDERSON-COUGHLIN, BREINNA - University Of Delaware; CRAIGHEAD, SHANI - University Of Delaware; GARTLEY, SAMANTHA - University Of Delaware; VANORE, ADAM - University Of Delaware; KNIEL, KALMIA - University Of Delaware; SOLAIMAN, SULTANA - University Of Maryland; BUI, ANTHONY - University Of Maryland; CRADDOCK, HILLARY - University Of Maryland; KULKARNI, PRACHI - University Of Maryland; ROSENBERG-GOLDSTEIN, RACHEL - University Of Maryland; SAPKOTA, AMY - University Of Maryland

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2021
Publication Date: 10/31/2021
Citation: Acheamfour, C., Parveen, S., Hashem, F., Sharma, M., Gerdes, M., May, E.B., Rogers, K., Haymaker, J., Duncan, R., Foust, D., Tabodi, M., Bradshaw, R., Handy, E.T., East, C.L., Kim, S., Micallef, S., Callahan, M., Allard, S., Anderson-Coughlin, B., Craighead, S., Gartley, S., Vanore, A., Kniel, K.E., Solaiman, S., Bui, A., Craddock, H.A., Kulkarni, P., Rosenberg-Goldstein, R., Sapkota, A.R. 2021. Levels of Salmonella enterica and Listeria monocytogenes in alternative irrigation water vary nased on water source on the Eastern Shore of Maryland. Applied and Environmental Microbiology. 9:e00669-21. https://doi.org/10.1128/Spectrum.00669-21.
DOI: https://doi.org/10.1128/Spectrum.00669-21

Interpretive Summary: With the significant burden placed on traditional irrigation water sources due to water scarcity, increased demand, and more stringent regulations, exploration of non-traditional water sources for the irrigation of fresh produce has become an area of great interest. Foodborne pathogens like Salmonella enterica and Listeria monocytogenes have caused outbreaks of infections associated with contaminated produce in the past. These pathogens can contaminate non-traditional irrigation water sources (rivers, agricultural ponds, recycled water), which are more frequently used for irrigation of food crops. Results presented here indicate that levels of S. enterica and L. monocytogenes are dependent on the water type and location where they are collected, and that L. monocytogenes vary based on seasons collected. These results show that Salmonella is more prevalent in river water on the Eastern Shore of Maryland compared to L. monocytogenes, and surface waters had higher levels of these pathogens compared to reclaimed (recycled) waters. Reclaimed water sources had lower pathogen burdens than surface water sources and is appropriately suited for irrigation of produce from a microbiological perspective. These findings benefit farmers by identifying hazards in non-traditional and reclaimed waters to allow them to make informed decisions about irrigation water intended for fruit and vegetable crops.

Technical Abstract: Availability of traditional irrigation waters is becoming limited due to increasing pressure from water scarcity, increased demand, and more stringent regulations. These limitations are leading to increased interest in the use of non-traditional irrigation water sources for fresh produce. Determining if these non-traditional water sources contain foodborne pathogens is paramount. The purpose of this study was to determine the prevalence of two bacterial pathogens - Salmonella enterica and Listeria monocytogenes - in non-traditional irrigation water sources. Water samples (n=188) were collected over a two-year period (2016-2018) from two reclaimed water plants, 3 non-tidal freshwater rivers, and 1 tidal brackish river on Maryland’s Eastern Shore. Samples were collected by filtration using modified Moore swabs (MMS), analyzed by non-selective and selective enrichment and plating. Pathogen levels were quantified using a modified MPN procedure with three different volumes (10L, 1L and 0.1L). Overall, 65% (122/188) and 40% (76/188) of water samples were positive for S. enterica and L. monocytogenes, respectively. For both pathogens, MPN values varied among sites over the course of the study; ranging from 0 to 11 MPN/L. S. enterica and L. monocytogenes levels (MPN/L) were significantly (p < 0.05) greater for the non-tidal freshwater river sites and the tidal brackish river site compared to the reclaimed water sites, respectively. L. moncytogenes levels in water varied based on season. Filtration of 10 L led to a a significantly (p < 0.05) more likely detection of S. enterica compared to filtration 0.1 L. A poor statistical correlation between pathogen levels and individual water physio-chemical factors was found. This study shows that S. enterica and L. monocytogenes are present in non-traditional irrigation water sources on the Eastern Shore of Maryland.