Abstract
BackgroundTyphoid fever, caused by Salmonella enterica serovar Typhi (S. Typhi), is a major health problem especially in developing countries. Vaccines against typhoid are commonly used by travelers but less so by residents of endemic areas.MethodologyWe used single nucleotide polymorphism (SNP) typing to investigate the population structure of 372 S. Typhi isolated during a typhoid disease burden study and Vi vaccine trial in Kolkata, India. Approximately sixty thousand people were enrolled for fever surveillance for 19 months prior to, and 24 months following, Vi vaccination of one third of the study population (May 2003–December 2006, vaccinations given December 2004).Principal FindingsA diverse S. Typhi population was detected, including 21 haplotypes. The most common were of the H58 haplogroup (69%), which included all multidrug resistant isolates (defined as resistance to chloramphenicol, ampicillin and co-trimoxazole). Quinolone resistance was particularly high among H58-G isolates (97% Nalidixic acid resistant, 30% with reduced susceptibility to ciprofloxacin). Multiple typhoid fever episodes were detected in 22 households, however household clustering was not associated with specific S. Typhi haplotypes.ConclusionsTyphoid fever in Kolkata is caused by a diverse population of S. Typhi, however H58 haplotypes dominate and are associated with multidrug and quinolone resistance. Vi vaccination did not obviously impact on the haplotype population structure of the S. Typhi circulating during the study period.
Highlights
Typhi) is the bacterium responsible for typhoid fever, which affects more than 20 million people each year, resulting in over 200,000 deaths [1,2]
Typhi are frequently used by travelers to typhoid endemic areas [12], they are yet to be effectively harnessed for the protection of local, typhoid endemic populations [13]
We have recently identified hundreds of single nucleotide polymorphisms (SNPs) within the S
Summary
Typhi is transmitted by the fecal-oral route, the typhoid fever burden falls almost exclusively in developing areas where sanitation is poor [1,3]. Children and young adults are the most vulnerable population for developing typhoid fever [1,8,9] and can be protected by vaccination against S. Typhi are frequently used by travelers to typhoid endemic areas [12], they are yet to be effectively harnessed for the protection of local, typhoid endemic populations [13]. Typhoid fever, caused by Salmonella enterica serovar Typhi Typhi), is a major health problem especially in developing countries. Vaccines against typhoid are commonly used by travelers but less so by residents of endemic areas
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