Determination of Adhesin Encoding Genes in Escherichia coli Isolates from Omphalitis of Chicks

Problem statement: Omphalitis is one of the most common causes of mortality in chicks during the first week after hatching. Escherichia coli strains are the most common isolated bacteria from omphalitis cases of chickens. Bacterial colonization in the host cells surfaces is a critical first step in the pathogenesis of avian pathogenic Escherichia coli isolates. Thus the current study was undertaken to determine the presence and prevalence of several adhesin-encoding genes in E. coli isolates from omphalitis of chicks. Approach: One hundred four E. coli isolates were recovered from omphalitis cases and were identified by standard biochemical tests. The omphalitis-derived isolates were examined for the presence of fimbrial and non-fimbrial adhesin-encoding genes by PCR technique. Results: Most (93.26%) of the E. coli isolates exhibited at least one of the examined adhesin-encoding genes. None of the isolates contained the afaI B-C, afa E-VIII and f17A genes. The two most prevalent genes were crl (87.50%) and fimH (77.88%). P (papC) and S (sfa) fimbriae encoding genes were detected in 8 (7.69%) and 5 (4.80%) isolates respectively. Seven combination patterns of the adhesin-encoding genes were detected. In 83 (79.80%) isolates combinations of 2-4 genes were detected. The gene combinations of crl-fimH and fimH-papC were the two most prevalent patterns respectively. Fourteen (13.46%) isolates showed crl gene alone and 7 (6.73%) isolates were negative for examined genes. Conclusion: The current study showed that some of the adhesinencoding genes are more prevalent in E. coli isolates from omphalitis of chicks but, E. coli isolates may be expressing still unknown adhesins that could have a role in the pathogenicity of omphalitisderived isolates.