A novel serovar of Shigella dysenteriae from patients with diarrhoea in Bangladesh

Abstract

Every year, around 3 % of isolates from patients with diarrhoea at Dhaka Hospital, ICDDR,B, are identified as Shigella-like organisms (SLOs) based on their activity in biochemical tests. These isolates do not react with any of the current Shigella antisera including all existing and provisional serotypes. Among these SLOs, a unique cluster of seven isolates with an identical plasmid profile was found and these isolates were further characterized by phenotypic and genotypic techniques. All were nonlactose fermenters, with an identical biochemical pattern typical of Shigella dysenteriae. They were classified as invasive since they harboured the 140 MDa invasive plasmid, were able to bind Congo red, produced keratoconjunctivitis in the guinea pig eye, and were positive by PCR for the ipaH gene and Shigella enterotoxin 2 [ShET-2] gene. All isolates were resistant to ampicillin, tetracycline and sulfamethoxazole-trimethoprim but were susceptible to mecillinam, nalidixic acid, ceftriaxone and ciprofloxacin. Six of the isolates were identical in DNA pattern by PFGE with the seventh exhibiting a closely related pattern; both patterns were distinguishable from all other Shigella and Escherichia coli patterns. An antiserum prepared against one of the isolates reacted with all isolates and did not cross-react with other Shigella and E. coli serotype reference strains. It is therefore proposed that these isolates represent a new provisional serovar of S. dysenteriae, type strain KIVI 162.

Novel strain of Shigella dysenteriae serotype 7 from India

“…They harbour many genetic elements on their invasion plasmid as well as on their chromosomes [1] . Isolation of atypical serotypes of S. flexneri have been reported from Korea, Russia, Bangladesh and China [3–6] , and a new serovar of S. dysenteriae has been reported from Bangladesh [7] . Here we report a strain of S. dysenteriae serotype 7 which had novel biochemical and virulence characters.…”

“…There is no record of set 1 (SheT1) being reported from S. dysenteriae in the literature. It has previously been reported only from S. flexneri (commonly serotype 2a) [7,9,10] . Sequence BLAST analysis of the target genes set 1A, set 1B and ipaH matched with that of GenBank accession number CP004057 , and the ial gene matched with that of GenBank accession number NC016833.…”

“…Missing such variant strains could result in a serious public health problem [6,16] . Redefining the classification of Shigella by developing a comprehensive classification scheme using a combination of biochemical, serologic and molecular characters must be undertaken because more new variants are being discovered across the globe [7] .…”

Serogroup distribution of Shigella in Ile-Ife, southwest Nigeria

“…Subgroup A is referred to as S. dysenteriae, subgroup B as S. flexneri, subgroup C as S. boydii and subgroup D as S. sonnei. 10 Both S. sonnei and S. boydii are usually associated with mild illness of short duration in which the stool may be watery or bloody. 11 S. flexneri is generally more severe, lasts longer, causes dysentery more frequently and is the principal cause of endemic shigellosis in many developing countries.…”

Shigella flexneriinfection in a newly acquired rhesus macaque (Macaca mulatta)

“…Shigella is gram-negative bacterium that causes bacillary dysentery in human and non-human primates [1-4]. Shigella flexneri belonging to the B subgroup of the genus is a well-known pathogen for primates, chiefly responsible for morbidity and mortality in colonized monkeys [5].…”