Tracking antibiotic resistance genes and class 1 integrons in Escherichia coli isolates from wastewater and agricultural fields

Considering high concentrations of multidrug-resistant (MDR) bacteria and antibiotic resistance genes (ARGs) in wastewater, agricultural reuse of treated wastewater may be a public health threat due to ARGs dissemination in different environmental compartments, including soil and edible parts of crops. We investigated the presence of antibiotic-resistant Escherichia coli as an indicator bacterium from secondary treated wastewater (STWW), water- or wastewater-irrigated soil and crop samples. ARGs including bla(CTX-m-32), bla(OXA-23), tet-W, sul1, cml-A, erm-B, along with intI1 gene in E. coli isolates were detected via molecular methods. The most prevalent ARGs in 78 E. coli isolates were sul1 (42%), followed by bla(CTX-m-32) (19%), and erm-B (17%). IntI1 as a class 1 integrons gene was detected in 46% of the isolates. Cml-A was detected in STWW isolates but no E. coli isolate from wastewater-irrigated soil and crop samples contain this gene. The results also showed no detection of E. coli in water-irrigated soil and crop samples. Statistical analysis showed a correlation between sul1 and cml-A with intI1. The results suggest that agricultural reuse of wastewater may contribute to the transmission of ARB to soil and crop. Further research is needed to determine the potential risk of ARB associated with the consumption of wastewater-irrigated crops.