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Identification and characterization of an RTX toxin in the emerging pathogen Kingella kingae

Thomas E Kehl-Fie1, Joseph W St Geme

  • 1Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63310, USA.

Journal of Bacteriology
|November 14, 2006
PubMed

Insights

Kingella kingae bacteria use an RTX toxin to cause harm. This toxin damages respiratory, joint, and immune cells, contributing to pediatric diseases like septic arthritis.

Area of Science:

  • Microbiology
  • Pathogenesis
  • Bacterial toxins

Background:

  • Kingella kingae is an emerging pathogen causing pediatric diseases such as septic arthritis and osteomyelitis.
  • Disease pathogenesis is thought to initiate with upper respiratory tract colonization.
  • K. kingae exhibits cytotoxicity towards respiratory epithelial cells, synovial cells, and macrophages.

Purpose of the Study:

  • To investigate the mechanisms behind K. kingae's cytotoxicity.
  • To identify the genetic basis of K. kingae's pathogenic effects.
  • To understand the role of specific toxins in K. kingae infections.

Main Methods:

  • Utilized mariner mutagenesis and cytotoxicity screening to identify genetic factors.
  • Conducted microscopy and lactic acid dehydrogenase (LDH) release assays to measure cytotoxicity.
  • Performed DNA sequence analysis and Southern blotting to characterize the identified genetic locus and related species.

Main Results:

  • A genetic locus encoding an RTX toxin system was identified in K. kingae.
  • Disruption of the RTX locus abolished cytotoxicity against epithelial, synovial, and macrophage cell lines.
  • Non-cytotoxic species, K. oralis and K. denitrificans, lacked the RTX region.
  • The RTX locus showed characteristics of horizontal gene transfer (insertion elements, reduced G+C content).

Conclusions:

  • Kingella kingae expresses a potent RTX toxin with broad cellular specificity.
  • This RTX toxin likely contributes to K. kingae pathogenesis by breaching epithelial barriers and damaging tissues.
  • The RTX toxin was likely acquired horizontally, representing a key virulence factor.

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