JCM Accepts, published online ahead of print on 17 June 2009

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J. Clin. Microbiol. doi:10.1128/JCM.00327-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Reliable Means of Diagnosis and Serovar Determination of Blood Borne Salmonella: Quick PCR Amplification of Unique Genomic Loci by Novel Primer Sets

Arvindhan Nagarajan, Guruswamy Karnam, Amit Lahiri, Uday Sankar Allam, and Dipshikha Chakravortty^*

^* To whom correspondence should be addressed. Email: dipa{at}mcbl.iisc.ernet.in.

Typhoid fever is becoming an ever increasing threat in the developing countries. We have improved considerably upon the existing PCR based diagnosis method by designing primers against a region which is unique to Salmonella enterica serovar Typhi (S. typhi) and Salmonella enterica serovar Paratyphi (S paratyphi A), corresponding to the gene STY0312 in S. typhi and its homolog SPA2476 in S. paratyphi A. An additional set of primers amplify another region in S. typhi CT18 and S. typhi Ty2 corresponding to the region between the genes STY0313 to STY0316 but which is absent in S. paratyphi A. The threat of false negative result arising due to mutation in hypervariable genes has been reduced by targeting a gene unique to typhoidal Salmonella as a diagnostic marker. The amplified region has been tested for genomic stability by amplifying them from clinical isolates of patients from various geographical locations in India, thereby showing that this region is potentially stable. These set of primers can also differentiate between S. typhi CT18, S. typhi Ty2 and S. paratyphi A which have stable deletions in this specific locus. The PCR assay designed in this study has a sensitivity of 95% as compared to the WIDAL test which had only 63%. As observed, in certain cases the PCR assay was more sensitive than the blood culture test as the PCR based detection could also detect dead bacteria.