Characterization of Shigella sonnei in Malaysia, an increasingly prevalent etiologic agent of local shigellosis cases

Abstract

BackgroundShigellosis is a major public health concern worldwide, especially in developing countries. It is an acute intestinal infection caused by bacteria of the genus Shigella, with a minimum infective dose as low as 10–100 bacterial cells. Increasing prevalence of Shigella sonnei as the etiologic agent of shigellosis in Malaysia has been reported. As there is limited information on the genetic background of S. sonnei in Malaysia, this study aimed to characterize Malaysian S. sonnei and to evaluate the prospect of using multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) for subtyping of local S. sonnei.MethodsForty non-repeat clinical strains of S. sonnei isolated during the years 1997–2000, and 2007–2009 were studied. The strains were isolated from stools of patients in different hospitals from different regions in Malaysia. These epidemiologically unrelated strains were characterized using biotyping, antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE) and MLVA.ResultsThe two biotypes identified in this study were biotype a (n = 29, 73%) and biotype g (n = 11, 27%). All the 40 strains were sensitive to kanamycin, ceftriaxone and ciprofloxacin. Highest resistance rate was observed for streptomycin (67.5%), followed by tetracycline (40%) and trimethoprim-sulfamethoxazole (37.5%). All the S. sonnei biotype g strains had a core resistance type of streptomycin - trimethoprim-sulfamethoxazole - tetracycline whereas the 29 biotype a strains were subtyped into eight resistotypes. All the strains were equally distinguishable by PFGE and MLVA. Overall, PFGE analysis indicated that S. sonnei biotype a strains were genetically more diverse than biotype g strains. Cluster analysis by MLVA was better in grouping the strains according to biotypes, was reflective of the epidemiological information and was equally discriminative as PFGE.ConclusionsThe S. sonnei strains circulating in Malaysia throughout the period studied were derived from different clones given their heterogeneous nature. MLVA based on seven selected VNTR loci was rapid, reproducible and highly discriminative and therefore may complement PFGE for routine subtyping of S. sonnei.

Shigella in Brazilian children with acute diarrhoea: prevalence, antimicrobial resistance and virulence genes

“…However, the development of molecular biology techniques has introduced genotyping methods with higher discriminatory power and better reproducibility (Navia et al 2005). Methods such as pulsed-field gel electrophoresis and multilocus variable number tandem-repeat analysis have been successfully employed to evaluate genetic diversity among Shigella populations (Filliol-Toutain et al 2011, Koh et al 2012. In this study, PCR was used to investigate virulence markers in Shigella isolates.…”

Recent Advances in Understanding Enteric Pathogenic Escherichia coli

“…being detected (455-458). However, a major shift from S. flexneri to S. sonnei is becoming more evident in transition countries and areas with improving socioeconomic conditions (454,459,460). In developed countries, S. sonnei is the most prevalent Shigella species and causes sporadic disease and outbreaks in epidemiological niches such as day care centers (461).…”

Caracterización molecular de aislamientos de Shigella sonnei recuperados en el Programa de Vigilancia por el Laboratorio de la Enfermedad Diarreica Aguda en Colombia

“…Con ello se contribuye a la investigación de brotes y Estos patrones electroforéticos reportados en otros países sin vinculación epidemiológica aparente pueden estar asociados con viajes de personas dentro de estos países o a zonas fronterizas, así como con fuentes comunes de infección, con el potencial de diseminación de diferentes clones que persisten durante largo tiempo y la transmisión de persona a persona de una cepa particular con cambios genéticos menores a lo largo de un extenso período, o con una combinación de todos estos eventos (35,36).…”