Virulence Genes Content and Antimicrobial Resistance in Escherichia coli from Broiler Chickens

A total of 121 E. coli strains were isolated from broiler chickens (96 extraintestinal pathogenic (ExPEC) strains from diseased broiler chickens and 25 avian fecal E. coli (AFEC) from healthy ones). Ten of the isolates (6 from diseased chickens and 4 from healthy birds) were serogrouped and 25 were examined for 4 virulence markers (tsh, papC, colV, and iss genes) as well as for their antimicrobial resistance. Five strains were nontypable and the rest were serotyped as follows: O86:K61 (2/5), O78:K80 (1/5), and O128:K67 (1/5) were recovered from diseased chickens, while O111:K58 strain (1/4) was isolated from healthy ones. The iss gene was found in 72.2% of the examined ExPEC strains in contrast to zero percentages (0%) in the AFEC strains, which may serve as a good marker for distinguishing APEC and its knocking out may help in creation of candidate vaccine that may prove sucess in elimination of infections in broiler chickens. Antimicrobial resistance patterns revealed a complete resistance to gentamicin, pefloxacin, amoxicillin, and enrofloxacin among examined strains followed by varying degrees of resistance for the rest of tested agents. The highest resistance was recorded against norfloxacin, in 24 isolates (96%), in contrast to the lowest resistance was recorded against colistin sulphate, in 14 strains (56%). These findings suggest the need for the prudent use of antimicrobials with broiler chickens and act as a warrant for the possibility of avian sources to transmit these resistant isolates to humans.