Persistent spatial patterns of Listeria monocytogenes and Salmonella enterica concentrations in surface waters: Empirical orthogonal function analysis of data from Maryland

Authors: KIM, SEONGYUN - U.S. DEPARTMENT OF AGRICULTURE (USDA); PAUL, MANASHI - UNIVERSITY OF MARYLAND; NEGAHBAN-AZAR, MASOUD - UNIVERSITY OF MARYLAND; MICALLEF, SHIRLEY - UNIVERSITY OF MARYLAND; ROSENGERG GOLDSTEIN, RACHEL - UNIVERSITY OF MARYLAND; HASHEM, FAWZY - UNIVERSITY OF MARYLAND EASTERN SHORE (UMES); PARVEEN, SALINA - UNIVERSITY OF MARYLAND EASTERN SHORE (UMES); SAPKOTA, AMIR - UNIVERSITY OF MARYLAND; KNIEL, KALMIA - UNIVERSITY OF DELAWARE; SAPKOTA, AMY - UNIVERSITY OF MARYLAND; Pachepsky, Yakov; Sharma, Manan

Submitted to: Applied Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2022
Publication Date: 7/26/2022
Citation: Kim, S., Paul, M., Negahban-Azar, M., Micallef, S., Rosengerg Goldstein, R., Hashem, F., Parveen, S., Sapkota, A., Kniel, K., Sapkota, A., Pachepsky, Y.A., Sharma, M. 2022. Persistent spatial patterns of Listeria monocytogenes and Salmonella enterica concentrations in surface waters: Empirical orthogonal function analysis of data from Maryland. Applied Sciences. 12:7526. https://doi.org/10.3390/app12157526.
DOI: https://doi.org/10.3390/app12157526

Interpretive Summary: Bacterial pathogens like Salmonella enterica and Listeria monocytogenes are present in non-traditional irrigation waters (rivers and ponds). These pathogens have caused fatal outbreaks associated with various contaminated fruits and vegetables in the past. Rivers and ponds are increasingly critical irrigation water sources for fruit and vegetable farmers as efforts are made to conserve groundwater. The research presented here compared survival patterns of these two pathogens in two river and two pond water sources to rainfall patterns. Land use characteristics were also determined for their potential effect on pathogen survival patterns. Overall survival and prevalence of both pathogens were lower in agricultural ponds compared to rivers examined in the study. Survival patterns for L. monocytogenes at pond water sites were similar to rainfall patterns; however, survival patterns for Salmonella enterica were related to rainfall only when examining how much pathogen levels and rainfall amounts deviated from mean values. Land use characteristics shows that the river site with the higher levels of L. monocytogenes were dominated by deciduous forest land, while the river site with higher S. enterica levels had more agricultural land use. These research results aid farmers to identify weather and land use factors that affect the prevalence of bacterial foodborne pathogens in river and pond water, and to implement appropriate mitigation strategies to minimize foodborne contamination in fruit and vegetable fields.

Technical Abstract: Levels and prevalence of Salmonella enterica and Listeria monocytogenes in ponds and rivers may be affected by environmental factors. Empirical Orthogonal Function (EOF) analysis can provide spatial and temporal patterns of variability to assess the effect of specific environmental factors on pathogen levels in water. The objective of this work was to examine the spatial and temporal pattens of Salmonella enterica and Listeria monocytogenes and interactions with rainfall using EOF analysis, while investigating the effect of land-use type in influencing S. enterica and L. monocytogenes levels. or prevalence in irrigation water. S. enterica and L. monocytogenes (MPN/L) values were determined from two river (MA04, MA05) and two pond (MA10, MA11) irrigation water sources. EOF analysis was used to interpret spatial and temporal patterns of pathogen levels in water based on rainfall data. The EOF1 of the one-day and seven-day rainfall had similar patterns to the EOF1 for L. monocytogenes at pond water sites, indicating that rainfall events increased levels of L. monocytogenes in ponds; however, L. monocytogenes EOF patterns in river water had a lower correlation with EOF rainfall patterns. EOF1 and EOF2 values for L. monocytogenes explained 84.4% and 9.7% of the total variance, respectively. EOF1 and EOF2 values for S. enterica explained 50.8% and 45.0% of the total spatial variance, respectively. S. enterica EOF2 patterns from MA04, MA05, and MA11 were similar to EOF2 patterns for rainfall, indicating a strong relationship between rainfall and Salmonella at these sites. Patterns of deviations of pathogen levels from the mean showed a close relationship with the patterns of the deviations of rainfall amounts the means across the sites. Overall, the rainfall data provided site-specific data but limited opportunities for prediction of pathogen levels across all water sources.