Prevalence of shiga-toxigenic and atypical enteropathogenic Escherichia coli in untreated surface water and reclaimed water in the Mid-Atlantic U.S

Authors: HAYMAKER, JOSEPH - University Of Maryland Eastern Shore (UMES); Sharma, Manan; PARVEEN, SALINA - University Of Maryland Eastern Shore (UMES); HASHEM, FAWZY - University Of Maryland Eastern Shore (UMES); MAY, ERIC - University Of Maryland Eastern Shore (UMES); Handy, Eric; WHITE, CHANELLE - University Of Maryland Eastern Shore (UMES); East, Cheryl - Roberts; BRADSHAW, RHODEL - University Of Maryland; MICALLEF, SHIRLEY - University Of Maryland; CALLAHAN, MARY THERESA - University Of Maryland; ALLARD, SARAH - University Of Maryland; ANDERSON, BRIENNA - 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; MURRAY, RIANNA - University Of Maryland; CRADDOCK, HILLARY - University Of Maryland; KULKARNI, PRACHI - University Of Maryland; FOUST, DEREK - University Of Maryland Eastern Shore (UMES); DUNCAN, RICO - University Of Maryland Eastern Shore (UMES); TAABODI, MARYAM - University Of Maryland Eastern Shore (UMES); SAPKOTA, AMY - University Of Maryland

Submitted to: Environmental Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2019
Publication Date: 2/13/2019
Citation: Haymaker, J., Sharma, M., Parveen, S., Hashem, F., May, E.B., Handy, E.T., White, C., East, C.L., Bradshaw, R., Micallef, S., Callahan, M., Allard, S., Anderson, B., Craighead, S., Gartley, S., Vanore, A., Kniel, K.E., Solaiman, S., Bui, A., Murray, R.T., Craddock, H.A., Kulkarni, P., Foust, D., Duncan, R., Taabodi, M., Sapkota, A.R. 2019. Prevalence of shiga-toxigenic and atypical enteropathogenic Escherichia coli in untreated surface water and reclaimed water in the Mid-Atlantic U.S. Environmental Research. 172:630-636. https://doi.org/10.1016/j.envres.2019.02.019.
DOI: https://doi.org/10.1016/j.envres.2019.02.019

Interpretive Summary: Shiga-toxigenic Escherichia coli (STEC) have been responsible for causing large scale outbreaks with leafy greens in the U.S. over the last decade, which have cause severe health issues. Seven serogroups of STEC have been responsible for about 70% of cases of illness caused by STEC, making these groups (“Big 7”) a heightened public health concern. Contaminated irrigation water is one route that these pathogens may be introduced to leafy greens, which are consumed without a step to kill these pathogens if present on the commodity. Many fruit and vegetable growers in the Mid-Atlantic region of the U.S. use surface waters for irrigation. Reclaimed waters may be considered a non-traditional source of irrigation as traditional sources (well water, surface waters, municipal waters) become prioritized for non-agricultural uses. Our study investigated the prevalence of STEC in untreated surface and reclaimed water samples in the Mid-Atlantic, taking water samples (10 L) from 11 sites either twice a week or once a month, depending on the season. Our results showed that 2.5% (12/483) of water samples tested were positive for STEC; however, none of these STEC isolates belonged to the “Big 7” serogroups. In addition, a lesser known pathotype of E. coli – atypical enteropathogenic E. coli (aEPEC) – was present in 11.6% (56/483) water samples. Atypical EPEC do not cause the same degree of foodborne illness that STEC cause. STEC were not as widely distributed aEPEC in our 12-month study, with the majority of samples positive for STEC isolates coming from two sites at two different dates of analysis. Overall, the prevalence of STEC is relatively low in the Mid-Atlantic region of the U.S., but growers should still be vigilant about the microbial quality of untreated surface irrigation water.

Technical Abstract: The microbial quality of irrigation water has increasingly become a concern as a source of contamination for fruits and vegetables. Non-traditional sources of water are being used by more and more growers in smaller, highly diversified farms in the Mid-Atlantic region of the U.S. Shiga-toxigenic E. coli (STEC) have been responsible for several outbreaks of infections associated with the consumption of leafy greens. Our study evaluated the prevalence of the “big seven” STEC serogroups and the associated enterohemorrhagic E. coli (EHEC) virulence factors (VF) genes in nontraditional irrigation waters in the Mid-Atlantic region of the U.S. Water samples (n=483) from 161 sampling events were collected from eight untreated surface water sites, two wastewater reclamation facilities, and one vegetable processing plant, over a 12 month-period. A total of 2489 presumptive STEC isolates were tested for the presence of the most frequently reported STEC serogroups that cause foodborne illness: O26, O45, O103, O111, O121, O145, and O157, along with the VF genes stx1, stx2, eae, and ehxA. Only 28 isolates contained one of the seven STEC serogroup genes, while 122 isolates contained one STEC-associated VF gene, with eae (n=88) being the most frequently detected EHEC VF. From the water samples, 2.5% (12/483) contained an STEC isolate, while 11.6% (56/483) contained an atypical enteropathogenic E. coli (EPEC) isolate. Isolates which contained for stx1 or stx2 genes mainly came from two sites on two sampling dates, indicating that these isolates were not spatially or temporally distributed among the sampling sites. STEC isolates at reclaimed water sites may have been introduced after wastewater treatment. The 78 isolates which solely contained eae were determined to be atypical EPEC and not E. albertii. Our work showed that STEC prevalence in Mid-Atlantic untreated surface waters over a 12-month period was lower than the prevalence of atypical EPEC.