Antimicrobial resistant Escherichia coli prevalence in freshwaters in Belgium and human exposure risk assessment

The objective of this work was to evaluate the antimicrobial resistant (AR) E. coli prevalence in recreational waters in Belgium and to assess the exposure risk for bathers. Nine stations were sampled during the 2021 bathing season. A total of 912 E. coli strains were isolated and tested by the disk diffusion method in accordance with EUCAST recommendations, including ExtendedSpectrum Beta-Lactamase (ESBL) production. AR E. coli were counted at each bathing sites, 24% of strains were resistant to at least one antibiotic and 6% were Multi-Drug Resistant (MDR). A Multiple Antibiotic Resistance (MAR) index was calculated to compare the bathing sites. The Lesse river had the highest MAR index as well as the highest E. coli absolute abundance and the largest number of ESBL-producing E. coli. Conversely, the 3 lakes showed lower E. coli contamination levels and AR rates. A human health risk assessment of exposure to AR E. coli, based on the calculation of measured prevalence, was performed considering four different dose-response model scenarios. The human health risk (Pd) ranged from 10-9 to 0.183 (children). The exposure probabilities were low, except for scenario 3 (E. coli O157:H7), which is the most severe.

Automated summary

The study aimed to evaluate the prevalence of antimicrobial resistant E. coli in recreational waters in Belgium and assess the risk of exposure for bathers. 24% of the E. coli strains tested were resistant to at least one antibiotic, and 6% were Multi-Drug Resistant (MDR). The Lesse river had the highest MAR index, E. coli abundance, and number of ESBL-producing E. coli, while the 3 lakes showed lower contamination levels and AR rates. A human health risk assessment based on the measured prevalence indicated low exposure probabilities, except for scenario 3 (E. coli O157:H7), which had the highest risk.