Work

Elevated Antibiotic Resistance in Escherichia coli from Surface Waters Impacted by Concentrated Animal Feeding Operations in California and Michigan

Year: 2026

Type: article

Abstract: Monitoring of antimicrobial resistance (AMR) in the environment is needed, but standardized methods are lacking. This study evaluated a cost-efficient, kit-based approach for detecting antibiotic-resistant Escherichia coli (AR-E. coli) and predicting multidrug-resistant E. coli (MDR-E. coli) in concentrated animal feeding operations (CAFO)-impacted surface waters in Tulare, California, and Clayton, Michigan. Eighteen Tulare and six Clayton samples were analyzed using modified IDEXX Colilert-18 kits with selective antibiotics. In Round 1 of the study, 702 isolates were tested against 12 antibiotics using disk diffusion to identify ideal additions. No and low resistance to AMP was seen at the unimpacted and less-impacted sites, respectively, while up to 34% of isolates at impacted sites were resistant to AMP. The percentage of isolates resistant to erythromycin was 16% or lower at less-impacted sites, but it ranged up to 64% at impacted sites. In Round 2, 1002 isolates (1704 total) were characterized to compare modified IDEXX results with culture-based results. Resistance to ampicillin (AMP-E. coli-col) detected by IDEXX strongly correlated with MDR prevalence in Clayton (R2 = 0.71, p = 0.00197), while extended-spectrum beta-lactamase-producing E. coli (ESBL-E. coli-col) correlated with MDR prevalence in Tulare (R2 = 0.70, p < 0.0001). This observation appears to be site-specific. Findings suggest both IDEXX- and culture-based methods can serve as AMR screening tools at CAFO-impacted sites. This work supports community-based monitoring and informs standardized approaches for tracking AMR in inland waters.

Source: Water

DOI: 10.3390/w18020207