Single Nucleotide Polymorphism Typing and Genetic Relationships of Salmonella enterica serovar Typhi Isolates

School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia

^* To whom correspondence should be addressed. Email: r.lan{at}unsw.edu.au.

	Abstract

Salmonella enterica serovar Typhi is a clone with low level of variation. We developed a molecular typing method for Typhi using 38 genome-wide single nucleotide polymorphisms (SNPs) as markers detected by PCR-restriction enzyme digestion. The 73 worldwide Typhi isolates studied were separated into 23 SNP profiles and four distinct genetic groups. Typhi isolates expressing the unique flagellar antigen z66 were found to be clustered together and branched off from the ancestral group, suggesting that Typhi was initially monophasic with only an H1 antigen and subsequently gained the z66 antigen. Typing using the 38 SNPs gave a discriminatory power of 0.87 and a minimum of 16 SNPs may be used to achieve the same level of differentiation. The SNP typing method we developed will be a valuable tool for global epidemiology of Typhi.