Comparison of Plasmid Profile Analysis, Serotyping, and Antimicrobial Resistance Patterns of E.Coli Isolated from Poultry in Tehran

INTRODOCTION: Colibacillosis is a common systemic infection caused by E. Coli in poultry. The disease is economically important for poultry producers. In the past strain identification was limit to serotyping and determination of antimicrobial resistance patterns which is not of great value because an identical resistance pattern does not prove that the strains are identical. In present study we compared serotype, antimicrobial resistance pattern, plasmid DNA profiling along with restriction endonuclease analysis for subtyping E. Coli isolated form poultry. A total of 50 strains of E.Coli, was isolated from bile and liver of poultry in several aviaries in Tehran between 1 October 2001 and 15 January 2002. Isolation and identification of strains was carried using standard procedures. Serotyping was performed by agglutination test using the Mst Diagnostic Kit (Mast Group Ltd., Mersey side, UK). Using monovalent and polyvalent serums of the kit only O6 serotype was determined. Serotyping was not possible for all of the isolated strains using the above menthioned kit. All clinical isolated serotypes were routinely tested by single-disk diffusion method against the commonly used antimicrobial agents. 50 strains of E.Coli showed 10 different resistance patterns. The most common antimicrobial resistance pattern was Tiamulin/ Flumequine/ Tetracycline/ Oxytetracycline/ Rifampicin/ Sxt/ Enrofloxacin (28%). Plasmid DNA was extracted by modification of the Birnboim and Doly technique. Isolated Plasmids were separated by electrophoresis on a 0.8% agarose gel in TBE buffer. In all the screened E.Coli strains plasmid of different molecular size were found. Plasmid profile distinguished more strains than did antimicrobial resistance pattern. In 50 E.Coli isolates which showed 10 different patterns of resistance, we found 25 plasmid profiles. Plasmid preparations were further compared by restriction endonuclease digestion, using Hind III, HindII, and EcoRI. In some cases restriction endounclease analysis in one banding pattern plasmid profiles showed heterology between plasmids. In this study Plasmid profile analysis distinguished more strains of E.coli from poultry in comparisom to antimicrobial resistance pattern and serotyping.