Journal of Bacteriology & Parasitology

Significance of Vi negative isolates of Salmonella enterica serovar Typhi in causing typhoid fever

3^rd International Congress on Bacteriology and Infectious Diseases

August 04-06, 2015 Valencia, Spain

Abdul Haque

Posters-Accepted Abstracts: J Bacteriol Parasitol

Abstract:

Typhoid is a major bacterial disease affecting 33 million people globally each year. Traditionally, pathogenicity of typhoid
bacillus has been attributed to Vi (Virulence) capsular antigen. However, we in collaboration with Imperial College, London
reported that Vi negative isolates occur naturally and can cause disease. They may make up to 25% of all isolates in some areas.
These findings were subsequently substantiated by reports from Nepal and India. It has been found that Vi antigen is not
required for causing disease. These findings have completely changed the perception of typhoid vaccine because all current
vaccines are based on Vi capsule which are ineffective against Vi negative isolates. This provides selective advantage and they
may emerge as a major global threat. We developed diagnostic tools for rapidly differentiating between these isolates. We have
focused on establishing conjugate vaccine candidates based on LPS of outer membrane which are present in all Salmonella Typhi
isolates whether they are Vi positive or Vi negative and can be used universally. We have also focused on structural differences
among these variants by using techniques such as GC-MS and NMR.