Abstract
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.
Highlights
Avian pathogenic Escherichia coli (APEC), a subgroup of extraintestinal pathogenic E. coli (ExPEC), enters through different routes including respiratory and genital tracts and causes various extraintestinal diseases collectively termed as colibacillosis in chickens, which are responsible for significant economic losses in the chicken industry [1,2,3]
Five were nontypeable and the rest belonged to 4 serotypes: O86:K61 (2/5), O78:K80 (1/5), and O128:K67 (1/5) were recovered from extraintestinal origins in diseased birds, while O111:K58 strain (1/5) was isolated from intestinal contents of healthy ones
The results showed a high degree of resistance to the examined antimicrobial agents; 25 (100%) isolates showed complete resistance to gentamicin, pefloxacin, amoxicillin, and enrofloxacin, 24 (96%) isolates were resistant to norfloxacin, 23 (92%) isolates were resistant to neomycin and flumequine, 22 (88%) isolates were resistant to oxytetracycline and streptomycin and doxycycline, 21 (84%) isolates were resistant to sulfamethoxazole and trimethoprim (SXT), 19 (76%) isolates were resistant to cefotaxime, and 14 (56%) isolates were resistant to colistin sulphate (Figure 5)
Summary
Avian pathogenic Escherichia coli (APEC), a subgroup of extraintestinal pathogenic E. coli (ExPEC), enters through different routes including respiratory and genital tracts and causes various extraintestinal diseases collectively termed as colibacillosis in chickens, which are responsible for significant economic losses in the chicken industry [1,2,3]. The pathogenicity of avian pathogenic E. coli (APEC) that permits certain intestinal commensal E. coli to become APEC and infect extraintestinal niche is the result of the expression of several putative virulence factors [4,5,6,7]. These virulence traits can be categorized as adhesion, iron acquisition, hemolysis, protection from bactericidal host factors, and toxin production [4, 8]. Antimicrobial therapy is one of the primary control measures for reducing the morbidity and mortality caused by APEC infections. Since the indiscriminate use of antimicrobials leads to the selection of resistant isolates, they need to be used prudently in order to preserve their therapeutic usefulness in both animals and humans [15]
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