Molecular detection of all 34 distinct O-antigen forms of Shigella

Abstract

Shigella is the cause of shigellosis or bacillary dysentery, the occurrence of which is estimated to be 165 million cases per year worldwide, resulting in 1.1 million deaths. Rapid and reliable assays for detecting and identifying Shigella in food, environmental and clinical samples are therefore necessary. Shigella species are traditionally identified by their O antigens. This study developed a DNA microarray targeting O-serotype-specific genes to detect all 34 distinct O-antigen forms of Shigella, including Shigella boydii types 1–18, Shigella dysenteriae types 1–13, Shigella flexneri types 1–5 and 6, and Shigella sonnei. A total of 282 strains were used to test the specificity of the microarray, including 186 Shigella and Escherichia coli representative strains, 86 Shigella clinical isolates and ten strains of other bacterial species that are commonly isolated from food or clinical stool specimens. The oligonucleotide probes were printed on the microarray in concentrations from 1 to 100 μM, and 10 μM proved to be the optimal probe concentration. The detection sensitivity for each serotype was 50 ng genomic DNA or 1 c.f.u. in 25 g milk powder sample following a 6 h enrichment in broth. The microarray is specific, sensitive and reproducible, and, to our knowledge, is the first report of a microarray for serotyping all O-antigen forms of Shigella.

Development of a Multiplex PCR Assay Targeting O-Antigen Modification Genes for Molecular Serotyping of Shigella flexneri

“…Primers used in the present study are listed in Table 3. Primers used for the amplification of the O-antigen flippase gene wzx were from Li et al (11). The other primers were designed for our study based on the sequences of the S. flexneri serotype-specific genes gtrI, gtrIC, gtrII, oac, gtrIV, gtrV, and gtrX.…”

Recent Advances in Understanding Enteric Pathogenic Escherichia coli

“…In these cases the PCR-based detection of the lysine decarboxylase cadA gene, which is mostly absent in Shigella but often present in EIEC, may provide better distinction (413,430). In general, genotypic analyses, such as MLST, provide higher resolution, which allows discrimination between Shigella and EIEC.…”

“…EIEC comprises 21 major serotypes, which are typically defined by their O-antigen pattern, with a few exceptions that also present H antigens (410) ( Table 4). Some of the EIEC O antigens are identical or closely related to Shigella O antigens and thus complicate the discrimination between EIEC and Shigella in conventional serotyping (412,413) (Table 4). Traditionally, Shigella is classified based on biochemical, serological, and clinical phenotypes, not on phylogenetic correlation (411,414,415).…”

“…Some antisera cross-react with O antigens of both EIEC and Shigella (412,413) (Table 5). In these cases the PCR-based detection of the lysine decarboxylase cadA gene, which is mostly absent in Shigella but often present in EIEC, may provide better distinction (413,430).…”

Exploration of Specific DNA-Barcodes in Shigella dysenteriae Using In-silico Analysis

“…Accumulation of 10 to 100 of these bacteria could cause shigellosis (3). Shigella is categorized to 4 groups, through biochemical and O antigen characteristics, including S. dysenteriae (group A), Shigellaflexneri (group B), Shigella boydii (group C), and Shigella sonnei (group D) (4)(5)(6). Shigella cells include a virulent plasmid that encodes genes that are necessary for attacking Intestinal mucosal cells (7).…”