Frequency of selected virulence-associated genes in intestinal and extra-intestinal Escherichia coli isolates from chicken

Abstract

<strong>Background:</strong> Although <em>Escherichia coli</em> (<em>E. coli</em>)<br />is a part of intestinal normal microflora of warm-blooded animals, including<br />poultry, outbreaks occur in poultry raised below standard sanitation and during<br />the course of respiratory or immunosuppressive diseases. Avian pathogenic <em>E.<br />coli</em> (APEC) harbors several genes associated with virulence and<br />pathogenicity. APEC strains are responsible for some diseases in poultry<br />including colibacillosis, swollen head syndrome, yolk sac infection, omphalitis<br />and coli granuloma. <strong>OBJECTIVES: </strong>The<br />aim of this study was examination of the presence and frequency of three<br />important virulence genes in intestinal and extra-intestinal (liver) <em>E. coli</em><br />isolates from chicken of Khuzestan province in the southwest of Iran. <strong>METHODS:</strong><br />Totally 120 (60 intestinal and 60 liver) <em>E. coli</em> isolates were examined<br />by polymerase chain reaction (PCR) for the presence of aerobactin (iutA),<br />temperature sensitive hemagglutinin (tsh) and fimbriae type 1 (fimH )<br />genes. <strong>RESULTS:</strong> The results showed<br />that tsh, iutA and fimH are respectively present in 78.3%, 70% and 61.7% of<br />liver isolates while in intestinal ones the frequency of these genes was 21.7%,<br />41.7% and 41.7% respectively. The most prevalent genotypes in extra intestinal<br />and intestinal isolates were tsh+fimH+iutA+ and tsh-fimH-iutA-respectively. <strong>CONCLUSIONS:</strong> It seems that these sets of virulence genes are significantly more<br />prevalent (P<0.05) in extra intestinal isolates and probably these genes<br />play an important role in the pathogenesis of APEC isolates in the southwest of<br />Iran. Although these virulence genes were not present in all APEC isolates their frequencies were high and using the<br />products of these genes in vaccines may be effective in protecting against<br />infections caused by this bacterium