Isolation of Shigella dysenteriae Type 1 and S. flexneri Strains from Surface Waters in Bangladesh: Comparative Molecular Analysis of Environmental Shigella Isolates versus Clinical Strains
AUTOR(ES)
Faruque, Shah M.
FONTE
American Society for Microbiology
RESUMO
Bacillary dysentery caused by Shigella species is a public health problem in developing countries including Bangladesh. Although, shigellae-contaminated food and drinks are often the source of the epidemic's spread, the possible presence of the pathogen and transmission of it through environmental waters have not been adequately examined. We analyzed surface waters collected in Dhaka, Bangladesh, for the presence of shigellae by a combination of PCR assays followed by concentration and culturing of PCR-positive samples. Analysis of 128 water samples by PCR assays for Shigella-specific virulence genes including ipaBCD, ipaH, and stx1 identified 14 (10.9%) samples which were positive for one or more of these virulence genes. Concentration of the PCR-positive samples by filtration followed by culturing identified live Shigella species in 11 of the 14 PCR-positive samples. Analysis of rRNA gene restriction patterns (ribotype) showed that the environmental isolates shared ribotypes with a collection of clinical isolates, but in contrast to the clinical isolates, 10 of the 11 environmental isolates were either negative or carried deletions in the plasmid-encoded invasion-associated genes ipaB, ipaC, and ipaD. However, all environmental Shigella isolates were positive for the chromosomal multicopy invasion-associated gene ipaH and all Shigella dysenteriae type 1 isolates were positive for the stx1 gene in addition to ipaH. This study demonstrated the presence of Shigella in the aquatic environment and dispersion of different virulence genes among these isolates which appear to constitute an environmental reservoir of Shigella-specific virulence genes. Since critical virulence genes in Shigella are carried by plasmids or mobile genetic elements, the environmental gene pool may contribute to an optimum combination of genes, causing the emergence of virulent Shigella strains which is facilitated in particular by close contact of the population with surface waters in Bangladesh.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=124020Documentos Relacionados
- Shigella dysenteriae Type 1-Specific Bacteriophage from Environmental Waters in Bangladesh
- Altering Trends in the Dominance of Shigella flexneri Serotypes and Emergence of Serologically Atypical S. flexneri Strains in Dhaka, Bangladesh
- Expression of Shigella dysenteriae serotype 1 O-antigenic polysaccharide by Shigella flexneri aroD vaccine candidates and different S. flexneri serotypes.
- Detection of Shigella dysenteriae type 1 and Shigella flexneri in feces by immunomagnetic isolation and polymerase chain reaction.
- In vitro adhesion and invasion inhibition of Shigella dysenteriae, Shigella flexneri and Shigella sonnei clinical strains by human milk proteins