Susceptibility Faecal Isolates of Commensal E. coli from Cattle to Fluoroquinolones and Cephalosporins

About 500 isolates of Escherichia coli were recovered from apparently healthy cattle and tested for their susceptibility to third generation cephalosporins and extended spectrum beta-lactamase producers were detected using the double dusk synergy test. Representative isolates were selected on the basis of their cephalosporin resistance patterns for plasmids analysis and mating experiment using E. coli 25922 as recipient. Resistance to cefoxitin was highest as 395 (79.0%) showed resistance to the antibiotic while resistance to ceftriaxone was the lowest with 87 (17.4%) isolates. Seventy two isolates were confirmed to be extended spectrum beta-lactamase producers. Two of 13 representative isolates selected among the extended spectrum beta lactamase producers carried single plasmids while the remaining 11 isolates contain multiple plasmids ranging from 1.2-22.2 kb. The cephalosporin-resistant isolates also carried plasmids with sizes ranging from 4.32-32 kb. Twelve isolates among the extended spectrum beta-lactamase producers that carried plasmids successfully transferred the plasmids to the recipient while all the cephalosporin-resistant isolates successful transferred plasmids to the recipient strain. The use of third-generation cephalosporins in animal medicine should be regulated.