A longitudinal assessment of Escherichia coli, total coliforms, Enterococcus and Aeromonas spp. dynamics in alternative irrigation water sources: A CONSERVE study

Authors: SOLAIMAN, SULTANA - University Of Maryland; ALLARD, SARAH - University Of Maryland; CALLAHAN, MARY THERESA - University Of Maryland; JIAN, CHENGSHENG - University Of Maryland; Handy, Eric; East, Cheryl - Roberts; HAYMAKER, JOSEPH - University Of Maryland Eastern Shore (UMES); BUI, ANTHONY - University Of Maryland; CRADDOCK, HILLARY - University Of Maryland; MURRAY, RIANNA - University Of Maryland; KULKURNI, PRACHI - University Of Maryland; ANDERSON-COUGHLIN, BRIENNA - University Of Maryland; CRAIGHEAD, SHANI - University Of Delaware; GARTLEY, SAMANTHA - University Of Delaware; VANORE, ADAM - University Of Delaware; DUNCAN, RICO - University Of Maryland Eastern Shore (UMES); FOUST, DEREK - University Of Maryland Eastern Shore (UMES); TAABODI, MARYAM - University Of Maryland Eastern Shore (UMES); SAPKOTA, AMIR - University Of Maryland; MAY, ERIC - University Of Maryland Eastern Shore (UMES); HASHEM, FAWZY - University Of Maryland Eastern Shore (UMES); PARVEEN, SALINA - University Of Maryland Eastern Shore (UMES); KNIEL, KALMIA - University Of Delaware; Sharma, Manan; SAPKOTA, AMY - University Of Maryland; MICALEF, SHIRLEY - University Of Maryland

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2020
Publication Date: 10/1/2020
Citation: Solaiman, S., Allard, S.M., Callahan, M., Jian, C., Handy, E.T., East, C.L., Haymaker, J., Bui, A., Craddock, H., Murray, R., Kulkurni, P., Anderson-Coughlin, B., Craighead, S., Gartley, S., Vanore, A., Duncan, R., Foust, D., Taabodi, M., Sapkota, A., May, E., Hashem, F., Parveen, S., Kniel, K., Sharma, M., Sapkota, A.R., Micalef, S.A. 2020. A longitudinal assessment of Escherichia coli, total coliforms, Enterococcus and Aeromonas spp. dynamics in alternative irrigation water sources: A CONSERVE study. Applied and Environmental Microbiology. https://doi.org/10.1128/AEM.00342-20.
DOI: https://doi.org/10.1128/AEM.00342-20

Interpretive Summary: Increasing demands for fresh fruit and vegetables, a variable climate impacting agricultural water availability and microbial food safety standards are all driving factors to identify new, safe, alternative sources of irrigation water. Groundwater, traditionally used for agricultural irrigation, and in some regions may be stressed by overuse. Since groundwater is resource built over time but consumed quickly, alternative irrigation waters (rivers, ponds, reclaimed water) should be evaluated for use in irrigation of fruit and vegetable crops. In this study, the microbial quality of several alternative sources of water were evaluated by determining levels of several taxa of bacteria commonly used as indicators of the presence pathogens or fecal contamination. Microbial data was collected over a two-year period from potential sources of irrigation (rivers, ponds and reclaimed water sites). Escherichia coli levels in pond water and reclaimed water was found to comply with proposed irrigation water of the Produce Safety Rule (PSR) of the Food Safety Modernization Act (FSMA) for irrigation of fruit and vegetables. E. coli levels, along with those of Enterococcus and total coliforms, showed the most variation in river water, which also contained the highest levels of these taxa. In several cases, river water would require mitigation before achieving compliance with the PSR. This dataset represents a comprehensive, longitudinal analysis of non-traditional irrigation water sources in the Mid-Atlantic United States. By quantifying levels of bacterial indicator organisms in alternative sources of irrigation water, this work aids growers and regulators in identifying sources which may require more mitigation before irrigation or harvest of fruits and vegetables.

Technical Abstract: As climate change continues to stress freshwater resources, we have a pressing need to identify alternative (non-traditional) sources of microbially safe water for irrigation of fresh produce. This study is part of the CONSERVE center, which aims to facilitate the adoption of adequate agricultural water sources. A 26-month longitudinal study was conducted at 11 sites to assess the prevalence of bacteria indicating water quality, fecal contamination and crop contamination risk (Escherichia coli, total coliforms (TC), Enterococcus, Aeromonas). Sites included non-tidal freshwater rivers/creeks (NF), a tidal brackish river (TB), irrigation ponds (PW) and reclaimed water sites (RW). Water samples were filtered for bacterial quantification. Taxa were widespread in water samples tested for E. coli, TC and enterococci (~86%, 98% and 90% positive, respectively; n=333), and Aeromonas (~98% positive; n=133). Highest E. coli counts were in rivers, TC counts in TB rivers and enterococci in rivers and ponds (all p<0.001), compared to other water types. Aeromonas counts were consistent across sites. Seasonal dynamics were detected in NF and PW samples only. E. coli counts were higher in the vegetable crop-growing (May-October) than non-growing (November-April) season in all water types (p<0.05). Eight water sites failed to meet the US Food Safety Modernization Act water standards, but implementation of recommended mitigation measures of allowing time for microbial die-off between irrigation and harvest, would bring all sites into compliance within two days. This study provides comprehensive microbial data on alternative irrigation water and will serve as an important resource for food safety planning and policy-setting.