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Indian Journal of Comparative Microbiology, Immunology and Infectious Diseases
Year : 2010, Volume : 31, Issue : 1and2
First page : ( 21) Last page : ( 24)
Print ISSN : 0970-9320. Online ISSN : 0974-0147.

In-vitro and in-vivo adhesion of avian pathogenic Escherichia coli to the surfaces of chicken tracheal epithelium

Pal Manju, Singh S.D., Dhama K.

Avian Disease Section, Division of Pathology, Indian Veterinary Research Institute, Izatnagar-243122, (Uttar Pradesh). sdsingh2005@rediffmail.com

Abstract

A total of 59 E. coli serotypes recovered from chickens, quail, Guinea fowls and turkeys with septicaemic lesions of colibacillosis were characterized on the basis of morphology, colony characteristics, biochemical profile and somatic ‘O’ antigen serotyping. These strains had thin pili (fimbriae) when grown at 37°C but not at 18°C. These pili facilitated adherence of the bacteria to chick tracheal epithelial cells both in-vitro and in-vivo. In-vitro fimbrial adherence to tracheal epithelium of 13 E. coli serotypes revealed 8 serotypes with high adhesiveness and 5 serotypes with low adhesiveness. These results were highly correlated with the presence of fimbriae on bacteria which indirectly related to mannose sensitive haemagglutination pattern (MSHA). In-vivo adherence of fimbriae on tracheal epithelium as observed by scanning electron microscopy revealed that piliated E. coli (grown at 37oC) were more virulent than nonpiliated ones (grown at 18oC). Adhesive properties were found in 87% of the lethal strains and in only 40% of the intermediate lethal strains. The role of these pili was also examined by comparing chicks infected intratracheally with piliated bacteria and non-piliated bacteria. It is suggested that adhesive property of E. coli strains with the help of pili (fimbriae) to the tracheal epithelium may play an important role in the virulence. PCR was also employed to detect the adhesin genes i.e. ‘crl’ and ‘csgA’. The result showed that 7 serotypes were found positive for ‘crl’ gene while 5 serotypes were positive for ‘csgA’ gene. Most of the isolates having ‘crl'genes was found to be positive for MSHA and adhesive, suggesting the role of curli gene in adherence and thus enhancing the virulence of the organisms. There has been a good correlation with MSHA and in-vitro adherence and a positive correlation was found between curli genes and adhesiveness.

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