ISOLATION AND MOLECULAR CHARACTERIZATION OF Escherichia coli AND Salmonella SPECIES FROM FOOD ANIMALS
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Date
2016-01
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College of Veterinary Science Assam Agricultural University Khanapara, Guwahati-781022
Abstract
The present study was carried out for isolation and molecular characterization of Escherichia coli and Salmonella species from faecal and meat samples of food animals viz. cattle, pigs and poultry.
Among the samples of 3 species of food animals examined, highest recovery of E. coli and Salmonella was made from faecal and meat samples of pigs.
All the 66 E. coli and 14 Salmonella isolates were confirmed by PCR using genus specific uidA and hisJ genes, respectively.
On serotyping, out of 66 E. coli isolates, 42 (63.64%) were typed into 13 different ‘O’ serogroups, 13 (19.70%) untypable and remaining 11 (16.67%) were identified as rough. Serogroup O84, O101, O118, O120 and O147 were predominant and serogroup O118 was recorded to be common in the samples of all 3 species of food animals.
Out of the 14 Salmonella isolates, 10 (71.43%) were recorded to be Salmonella Typhimurium and 2 (14.29% each) S. Enteritidis and S. Miami. S. Typhimurium was the most predominant serovar encountered in food animals and recorded to be the common serovar in pigs and poultry.
Twenty representative E. coli isolates from 20 different locations and 10 representative Salmonella Typhimurium isolates from 10 different locations were subjected for molecular typing by PCR targeting Repetitive Extragenic Palindromic (REP) sequences. On visual comparison, the multiple DNA fragments of E. coli, ranged in sizes between 100 to 1800 bp. Whereas, multiple DNA fragments of Salmonella Typhimurium, ranged in sizes between 100 to 1250 bp.
On analysis of dendrogram of E. coli isolates, the 17 band profiles were grouped into 2 major clusters viz. cluster A and cluster B at 4.88% similarity. The isolates that belonged to cluster A were specific for cattle and pigs while the cluster B were found to consist of only E. coli of poultry and pig origin. Likewise, dendrogram analysis of Salmonella Typhimurium isolates depicted 3 band profiles, which were grouped into two major clusters viz. cluster A and cluster B. The isolates that belonged to cluster A were specific for pigs and poultry while the cluster B were found to consist of only Salmonella Typhimurium of pig origin.
Virulent stx2 and est genes were detected from 5 and 3 E. coli isolates, respectively. Out of 5 stx2 positive E. coli isolates, 2 belonged to serotype O2 and O126 and 3 belonged to serotype O84 and untypable (2) which were recovered from cattle and pig faecal samples, respectively. Out of 3 est positive E. coli isolates, 2 each belonged to serotype O147 and untypable and 1 belonged to serotype O101 which were recovered from cattle faecal and pork samples, respectively.
All the 14 isolates of Salmonella showed to bear invA gene indicating that all the isolates are invasive in nature.
Antimicrobial sensitivity pattern of all the 66 E. coli and 14 Salmonella isolates against 7 different antimicrobial agents showed highest sensitivity to chloramphenicol and ciprofloxacin and least sensitivity to ampicillin and cloxacillin.
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