Escherichia coli (E.coli) is a normal intestinal microflora of birds, including ostrich. However, some strains are pathogenic to ostrich. There is a lack of knowledge concerning the differences between commensal and pathogenic E.coli isolates of ostrich. This research aimed to characterize the antimicrobial susceptibility profile and virulence gene content of presumptive commensal and pathogenic E.coli isolates of ostrich. A total of 129 bacterial isolates (commensal strains no. = 45; pathogenic strains no. = 84) were obtained from ostriches. The resistance profile of these isolates was investigated by the disk diffusion method and PCR. Also, the strains were screened for virulence-associated genes of avian pathogenic E.coli (APEC). The study showed that the highest and the lowest antimicrobial resistance were against oxytetracycline and gentamicin, respectively. Oxytetracycline, florfenicol, and streptomycin resistance rate in pathogenic isolates were higher than commensal ones (p < 0.05). Also, tetA, blaTEM, and aac(3)-IV resistance genes were more prevalent in pathogenic than commensal isolates (p < 0.05). More than half of the isolates had no virulence-associated genes. The multiplex PCR results showed that irp2 gene was more prevalent in pathogenic than commensal E.coli (p < 0.05). Nevertheless this was not the case with the other genes. Our results indicated a low frequency of antimicrobial resistance and virulence genes in E.coli isolates of ostriches. Antimicrobial susceptibility profile and virulence gene content of E.coli isolates of ostriches differ between presumptive commensal and pathogenic strains. However, more analyses are needed to discriminate these isolates.
Keywords: Antimicrobial susceptibility; Commensal E.coli; Ostrich; Pathogenic E.coli; Virulence genes.