Antibiotic Resistance in Surface Water

The aquatic environment has been recognized as a source of antibiotic
resistance (AR) that factors into the One Health approach to combat
AR. To provide much-needed data on AR in the environment, a
comprehensive survey of antibiotic-resistant bacteria (ARB),
antibiotic resistance genes (ARGs), and antibiotic residues was
conducted in a mixed-use watershed and wastewater treatment plants
(WWTPs) within the watershed to evaluate these contaminants in surface
water. A culture-based approach was used to determine the prevalence and
diversity of ARB in surface water. Low levels of AR _Salmonella_
(9.6%) and _Escherichia coli_ (6.5%) were detected, while all
_Enterococcus_ were resistant to at least one tested antibiotic. Fewer
than 20% of extended-spectrum β-lactamase (ESBL)-producing
[Enterobacterales] (17.3%) and carbapenem-resistant [Enterobacterales]
(CRE) (7.7%) were recovered. Six ARGs were detected using qPCR,
primarily the erythromycin-resistance gene, ermB. Of the 26
antibiotics measured, almost all water samples (98.7%) had detectable
levels of antibiotics. Analysis of wastewater samples from 3 WWTPs
showed that WWTPs did not completely remove AR contaminants. ARGs and
antibiotics were detected in all the WWTP effluent discharges,
indicating that WWTPs are the source of AR contaminants in receiving
water. However, no significant difference in ARGs and antibiotics
between the upstream and downstream water suggests that there are
other sources of AR contamination. The widespread occurrence and
abundance of medically important antibiotics, bacteria resistant to
antibiotics used for human and veterinary purposes, and the genes
associated with resistance to these antibiotics, may potentially pose
risks to the local populations exposed to these water sources.