Genetic diversity of Vibrio pathogenicity island in Vibrio cholerae isolates of clinical origin in Iran

Abstract number: R2360

Mohammadi Barzelighi H., Bakhshi B., Rastegar Lari A., Masjedian F., Pourshafie M.R.

Objective: Two important virulence factors of Vibrio cholerae strains includes cholera toxin and toxin coregulated pilus (TCP) encoded on Vibrio Pathogenicity Island (VPI). This region which is 41.2 kb in size encodes 29 proteins and including genes necessary for biogenesis of TCP which plays an important role in the colonisation of bacterium in the gut, biofilm formation and CTX prophage attachment. The aim of this study is to investigate the presence and diversity of the VPI in the Vibrio cholerae isolates of clinical origin from Iran.

Methods: 20 Vibrio cholerae isolates investigated in this study using biochemical and serological tests and subjected to analysis using Long-PCR analysis of the central region of the VPI including the complete TCP gene cluster. PCR products were subjected to Restriction Fragment Length Polymorphism (RFLP) analysis using EcoRI, EcoRV, ClaI, BglI and DdeI restriction enzymes. Left and right segments of VPI cluster were also subjected to analysis using 6 pairs of primers which spans the major gene clusters in these regions and also the integrase and joining sites of the cluster.

Results: Serogrouping revealed that 25% of isolates belonged to the O1 Ogawa, and 75% to the O1 Inaba serogroups. PCR analysis and subsequent RFLP of PCR products showed that 85,100,100, 76,100,100 and 80% of isolates possesed LJ, aldA, tagA, toxT, acfB-C, int and RJ regions, respectively. Long-PCR analysis and subsequent RFLP of product revealed that 100 and 100% of isolates possesed tcpI-F, tcpQ-R and tcpQ-F, tcpF-R, respectively, according to the standard strain ATCC 14035.

Conclusion: Results of this study emphasizes that, the integrity of TCP gene cluster is necessary for toxin coregulated pilus production and function and subsequent CTX prophage acquisition by V. cholerae and showes the low diversity of the left and right segments of this cluster. It seems that the ability of VPI for excision from the genome of the V. cholerae and some point mutations in the binding region of the primers stands for the absence of some of the fragments in a low percent of isolates and our data are in consistent with the hypothesis that the VPI can have a mosaic structure in some Vibrio cholerae strains and genotye diversity is due to the circulation of virulence genes.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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