Abstract : BACKGROUND Salmonella Typhi (S. Typhi) causes typhoid fever which remains an important public healt
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Abstract : BACKGROUND Salmonella Typhi (S. Typhi) causes typhoid fever which remains an important public health issue in many developing countries. Kathmandu the capital of Nepal is an area of high incidence and the pediatric population appears to be at high risk of exposure and infection.|METHODS We recently defined the population structure of S. Typhi using new sequencing technologies to identify nearly 2000 single nucleotide polymorphisms (SNPs) that can be used as unequivocal phylogenetic markers. Here we have used the GoldenGate (Illumina) platform to simultaneously type 1500 of these SNPs in 62 S. Typhi isolates causing severe typhoid in children admitted to Patan Hospital in Kathmandu.|RESULTS Eight distinct S. Typhi haplotypes were identified during the 20-month study period with 68 of isolates belonging to a subclone of the previously defined H58 S. Typhi. This subclone was closely associated with resistance to nalidixic acid with all isolates from this group demonstrating a resistant phenotype and harbouring the same resistance-associated SNP in GyrA (Phe83). A secondary clone comprising 19 of isolates was observed only during the second half of the study.|CONCLUSIONS: Our data demonstrate the utility of SNP typing for monitoring bacterial populations over a defined period in a single endemic setting. We provide evidence for genotype introduction and define a nalidixic acid resistant subclone of S. Typhi, which appears to be the dominant cause of severe pediatric typhoid in Kathmandu during the study period.|
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