Molecular description of alpha-hemolysin producing Escherichia coli isolates from extraintestinal source

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D. A. C. Dr. Vishwas Saralaya, “Molecular description of alpha-hemolysin producing Escherichia coli isolates from extraintestinal source”, ijmhs, vol. 8, no. 6, Jul. 2018.
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Abstract

Context: Alpha-hemolysin (Hly) is a common exotoxin produced by Escherichia coli, which plays an important role as a virulence factor in a number of clinical infections. There exist other virulence properties exhibited by such strains whose role in pathogenesis have not yet been clearly elucidated.

Aims: Aim of present study was to characterize those alpha-hemolysin producing isolates on the basis of their virulence factors and phylogenetic background.

Settings and Design: This descriptive study was carried out in a multi-specialty tertiary care hospital.

Methods and Material: Three hundred non-repeat E. coli isolates from in-patients were studied. Isolates were differentiated as haemolytic and non-haemolytic on the basis of both phenotypic methods such as haemolysis on sheep blood agar and genotypic detection of the hly gene. Possession of virulence and drug resistance genes was determined by multiplex polymerase chain reaction (PCR). Phylogenetic analysis was performed by triplex PCR methods. Antibiotic sensitivity testing was performed by disk diffusion method.

Results: Of the 300 isolates, it was observed that by phenotypic (haemolysis on blood agar) method, 65(22%) were hemolytic whereas the genotypic method detected 70 (23.5%) isolates possessing alpha haemolysin (hlyA+) marker. B2 phylogroup isolates were found to harbour the hlyA+ marker at a significantly higher (P < 0.05) rate.  The possession of papC and cnf1 genes was significantly higher in hlyA+ isolates.

Conclusions: Alpha-haemolysin producing isolates demonstrated higher virulence properties. The microbiology laboratory may report haemolytic characteristics of the isolates as it may alert the physician of the higher pathogenic potential of the strain and to initiate appropriate treatment.

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