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Colicin type 7 produced by majority of Shigella sonnei isolated from Thai patients with diarrhoea

Siriporn Kaewklom1, Seksun Samosornsuk2, Duangnate Pipatsatitpong2

  • 1Graduate Program in Biomedical Sciences, Faculty of Allied Health Sciences, Thammasat University, Rangsit Campus, Klonglaung, Pathumthai, Thailand.

Brazilian Journal of Microbiology : [Publication of the Brazilian Society for Microbiology]
|February 12, 2014
PubMed

Insights

Researchers identified Shigella sonnei strains from Thai diarrhea patients producing colicin type 7, a heat-stable bacteriocin effective against E. coli O157 and other Shigella species. This marks the first report of colicin type 7 in S. sonnei from this region.

Area of Science:

  • Microbiology
  • Bacteriology
  • Molecular Biology

Background:

  • Shigella sonnei is a significant cause of bacterial dysentery.
  • Antibiotic resistance in bacterial pathogens necessitates the exploration of alternative antimicrobial agents.
  • Bacteriocins, such as colicins, represent a promising class of proteinaceous toxins with antimicrobial properties.

Purpose of the Study:

  • To investigate the prevalence and characteristics of bacteriocin production in Shigella sonnei strains isolated from Thai patients with diarrhea.
  • To identify and characterize a specific bacteriocin, colicin type 7, produced by an S. sonnei isolate.
  • To assess the antimicrobial spectrum and stability of the purified bacteriocin.

Main Methods:

  • Isolation and screening of Shigella sonnei strains from clinical samples.
  • Agar well diffusion assays to determine antibacterial activity.
  • Polymerase Chain Reaction (PCR) to detect colicin genes.
  • Partial purification and characterization of bacteriocin, including enzymatic sensitivity, heat stability, pH stability, and molecular weight determination using SDS-PAGE.

Main Results:

  • Thirty-one out of 153 S. sonnei strains exhibited antibacterial activity.
  • All active strains harbored the colicin type 7 (Js) gene, with strain 35/44 producing the colicin type 7 lytic protein (cja).
  • The partially purified bacteriocin (PPB) showed activity against E. coli O157, S. sonnei, and S. boydii, was proteinaceous, heat-stable (up to 80°C), and stable across a pH range of 3-9.
  • SDS-PAGE analysis indicated a molecular weight of 54.4 kDa for colicin type 7, composed of at least five subunits.

Conclusions:

  • Shigella sonnei strain 35/44, isolated from Thai patients, produces a potent, heat-stable bacteriocin identified as colicin type 7.
  • This colicin exhibits activity against relevant Gram-negative pathogens, suggesting its potential as a therapeutic agent.
  • This study represents the first report of colicin type 7 in S. sonnei from Thai patients with diarrhea, highlighting a novel antimicrobial resource.
Keywords:
Shigella sonneicolicin type 7diarrhoea

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