Abstract
Shigellosis is a major public health concern worldwide. This study intended to assess the baseline genotyping data among local Shigella sonnei strains spanning over five years. Fifty non-repeat clinical strains of S. sonnei isolated from stools of patients in different hospitals in Nanjing, China, were studied. Three subtyping tools, pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), and multi-locus variable-number tandem-repeat (VNTR) analysis (MLVA), were used for routinely subtyping local S. sonnei. DNA sequencing only identified two sequence types (STs) among the 50 isolates in the MLST profiles, whereas PFGE and MLVA both showed suitable discriminatory power and yielded 19 and 30 different patterns, respectively. The major PFGE pattern comprised 21 strains isolated from different years. A total of four complexes were identified by MLVA, with the isolates differing by a single locus (single-locus variants). The S. sonnei strains circulating in Nanjing, China, in 2007-2011 originated from different clones with a degree of diversity. Most of the clones were closely related to each other. Overall, the strains were distinguishable by PFGE and MLVA. MLVA based on eight selected VNTR loci represented a more favorable degree of discrimination than did PFGE and may be a reliable complement for PFGE for routine subtyping of S. sonnei. The problems of MLST in subtyping regarding S. sonnei were also demonstrated.
Highlights
Shigellosis is a major public health concern worldwide
Though applied in a limited collection of S. sonnei isolates, our study suggests that these eight loci were sufficient for the subtyping of S. sonnei
Our results were somewhat consistent with the reports that pulsed-field gel electrophoresis (PFGE) may not be sufficiently discriminative for clonal research of S. sonnei strains that have evolved over very long time periods [9,21]
Summary
Shigellosis is a major public health concern worldwide. Results: DNA sequencing only identified two sequence types (STs) among the 50 isolates in the MLST profiles, whereas PFGE and MLVA both showed suitable discriminatory power and yielded 19 and 30 different patterns, respectively. The major PFGE pattern comprised 21 strains isolated from different years. Shigellosis continues to be a major public health concern worldwide, predominantly affecting children under five years of age in developing countries [1]. Recent surveillance data showed that the overall trend of shigellosis in China is declining, the disease remains more common than in developed countries and presents itself as a serious condition. The dominant Shigella species may be related to the location as well as to the stage of economic development. Increasing rates of S. sonnei cases were recorded in economically developed provinces in China between 2001 and 2010 [6]
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