Tracking phenotypic and genotypic characteristics of fecal Escherichia coli isolates: A comparative study between dairy cows and dairy farm workers.

The emergence of antibiotic-resistant Escherichia coli (E. coli) in humans and animals poses a major public health concern. Biofilm formation enhances bacterial survival and facilitates the dissemination of resistance and virulence determinants. This study characterized 157 fecal E. coli isolates (105 from cows, 42 from farm workers, and 10 from human controls) with respect to antibiotic resistance using cefotaxime, ceftazidime, meropenem, aztreonam, ciprofloxacin, fosfomycin, gentamicin, doxycycline, and nitrofurantoin disks, as well as extended-spectrum beta-lactamase (ESBL) production, biofilm formation, integron carriage, and virulence genes (fimH, csgA, papC, sfa/focDE, crl, afa, bcsA). Doxycycline resistance was most common across all groups. Multidrug resistance (MDR) was detected in 1% of cow isolates, 19% of farm worker isolates, and none of the controls. ESBL-producing isolates were found in 4.8% of cows, 28.6% of workers, and 30% of controls. Biofilm formation was observed in 17.1% of cow isolates, 23.8% of farm worker isolates, and 60% of controls, although most were weak producers. Class 1 and 2 integrons were present in 12.4% and 6.7% of cow isolates, 35.7% and 14.3% of farm worker isolates, and 40% and 20% of controls, respectively. Virulence genes were widespread, except sfa/focDE and afa. Compared with cow isolates, farm worker isolates exhibited significantly higher resistance but showed broadly similar biofilm and virulence traits. These findings highlight stronger selective antibiotic pressure in humans. The phenotypic and genotypic similarities between cow and farm worker isolates within the same farms underscore the need for further investigations.