Esherichia coli infections are a significant concern to the poultry industry. E.coli is a
common inhabitant of the gastrointestinal tract of most animals, including birds, but not
all E.coli isolates are capable of causing disease
1 . Avian pathogenic E.coli strains
(APEC) cause several disease syndromes in farmed birds such as peritonitis
2,
enteritis
3, airsacculitis, pericarditis, perihepatitis, salpingitis, synovitis, panophtalmitis
2-5 and swollen head syndrome
6 . The serological and bacteriological methods for
typing microbes are often limited to a few select reference laboratories. Such typing
precedures are not sensitive enough to further differentiate bacterial isolates. Bacterial
isolates including E.coli can be differentiated into genetically distinct isolates using
procedures that identify differences in the genetic composition of a microbial population.
These techniques involve multilocus enzyme electrophoresis (MLEE)
7 , pulsed-field
gel electrophoresis (PFGE)
8, random amplification of polymorphic DNA (RAPD)
9,
bacterial restriction endonuclease digest analysis (BRENDA)
10, or restriction
fragment length polymorphism (RFLP) analysis by either Southern blot or polymerase
chain reaction (PCR)
10.
Most pathogenic E.coli avian isolates cannot be distinguished biochemically from the
normal commensals inhabiting the gastrointestinal tract of birds. Diagnosis of E.coli
infection currently relies on the phenotypic differentiation of pathogenic strains from
nonpathogenic normal flora. Phenotypic differentiation methods can be time-consuming
and complicated and are not routinely used in many clinical laboratories. Genotypic
diagnosis may be accomplished by DNA colony blot hibridization to identify genes
encoding virulence factors11. Howewer, the use of radioactive isotopes and need for
more time make this method unsuitable for many diagnostic laboratories.
Various genotypic methods have been proven useful
for species identification, epidemiological typing and
determining the genetic relatedness among pathogenic
and nonpathogenic bacteria12,13.
Genotyping of E.coli strains may aid in defining those
that are specifically pathogenic for a certain host, and
give guidance for epidemiological studies of sources of
infection, and disease transmission. Using a molecular
approach, arbitrary amplification of polymorphic DNA
sequences, termed random amplification of polymorphic
DNA (RAPD) analysis on arbitrarily primed PCR (APPCR)
typing,9,13 is one such new technique that is
being used in many epidemiological studies. It is a fast,
PCR based method of genetic typing based on genomic
polymorphisms.
The purpose of the present study was to investigate
the genetic differences in local E.coli isolates from
colibacillosis suspicious hens.
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