A total number of 250 calves were subjected to thorough clinical examination and rectal swabbing for bacterial isolation. These calves were divided into two groups; the first one was123 calves which appeared healthy with shiny eyes and bloomy skin. The second group was 127 calves with diarrhea, different degrees of dehydration and most of them were separated from their dams before weaning age and did not take the colostrum. The most common bacterial isolates were Escherichia coli (E.coli) (100 isolates, 39.7%). The quinolone resistance phenotypes of E.coli isolates were recorded in 50 calves (42 diarrheic and 8 healthy calves); nalidixic acid (NAL 26%), norfloxacin (NOR 29%), ciprofloxacin (CIP 23 %) and enrofloxacin (ENRO 33%). PCR amplification reaction of twenty resistant E.coli isolates detected the plasmid- mediated quinolone resistance genes; qnrA, in four isolates (diarrheic calves) and aac(6)Ib-cr in sex isolates (four diarrheic and two of healthy calves). We concluded that several mechanisms of quinolones resistance are present in enteric E.coli from diarrheic as well as healthy calves. These resistances increase the public health hazard of these bacteria.
Key words: Calf, Diarrhea, E.coli, Quinolone resistance
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