Multidrug-Resistant Phenotypes and Resistance Gene Profiles of <i>Escherichia coli</i> Isolated from Healthy Calves in Panama

The presence of multidrug-resistant Escherichia coli strains in healthy cattle represents a major threat to public health because they can act as a reservoir of resistance genes. Little is known about the antimicrobial susceptibility profile and genetic characteristics of E. coli strains isolated from healthy calves in Panama and Central America. We conducted a cross-sectional study evaluating isolates from healthy calves in Panama. Antimicrobial susceptibility was determined against 15 antibiotics, and strains were classified as resistant, intermediate, or susceptible. 120 E. coli isolates were obtained, of which 61% were resistant to at least one antibiotics analyzed, while only 39% were susceptible. The most frequent resistance was to tetracycline (36%) and ampicillin (34%). Fifteen percent of the isolates (18/120) were multidrug-resistant, and 2% presented an extended spectrum β-lactamase phenotype; blaTEM (22%) and blaCTX-M (10%) genes were detected, with the Extended-Spectrum β-lactamases phenotype observed in isolates carrying blaCTX-M. Plasmid-mediated quinolone resistance gene qnrA (10%), qnrB (13%), and qnrS (23%) were detected among the isolates. Our results suggest that a significant proportion of antimicrobial resistance occurs in intestinal strains of E. coli isolated from healthy calves in Panama.