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

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