Salmonella enterica serovar Typhi variants in long-term carriers

Abstract

Long-term typhoid carriers can simultaneously excrete Salmonella enterica serovar Typhi variants with considerable genetic differences, a situation that complicates the interpretation of the subtyping data used in outbreak investigations and disease surveillance.

Fig 1

Genetic relatedness of Salmonella enterica serovar Typhi strains. (A) Dendrogram constructed using the PFGE-XbaI patterns of the strains from 3 clusters of infection. (B) Minimum spanning tree constructed using the MLVA profiles of 8 VNTR loci for the isolates from 3 clusters of infection and 57 isolates with the SIX.001 PFGE type recovered from other patients and asymptomatic carriers between 1998 and 2011. Each circle represents an MLVA type, and the size of the circle is proportional to the number of isolates belonging to the MLVA type. A distance of one locus between two MLVA types is indicated by a thick black line, a distance of two loci by a thin red line, a distance of three loci by a broken black line, and a distance of four or more loci by a numbered broken red line. The MLVA types for the 2 isolates from the carrier in cluster 2 and for the isolate from the patient in cluster 3 are indicated by green arrows. The MLVA types for the isolates from clusters 1, 2, and 3 are marked in green, yellow, and red, respectively, while those for other isolates with the SIX.001 type are marked in white.