Open AccessPrevalence of cdtABC genes encoding cytolethal distending toxin among Haemophilus ducreyi and Actinobacillus actinomycetemcomitans strains
Author(s) -
Hinda Ahmed,
Lars Svensson,
Leslie D. Cope,
Jo L. Latimer,
Eric J. Hansen,
Karin Ahlman,
J. Bayat-Turk,
Daniel Klamer,
Teresa Lagergård
Publication year - 2001
Publication title -
journal of medical microbiology/journal of medical microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 117
eISSN - 1473-5644
pISSN - 0022-2615
DOI - 10.1099/0022-1317-50-10-860
Subject(s) - haemophilus ducreyi , cytolethal distending toxin , microbiology and biotechnology , cytotoxic t cell , biology , titer , actinobacillus , gene , pasteurellaceae , toxin , chancroid , virology , bacteria , haemophilus influenzae , antibiotics , genetics , in vitro , microbial toxins , virus , syphilis , human immunodeficiency virus (hiv)
The aim of this study was to investigate the presence of the three cdtABC genes responsible for production of cytolethal distending toxin (CDT) in Haemophilus ducreyi and Actinobacillus actinomycetemcomitans strains. Of 100 H. ducreyi strains from the culture collection of the University of Göteborg (CCUG), 27 strains with low or intermediate cytotoxic titre (< 1 in 10(4)) and 23 of the remaining isolates with a high cytotoxic titre (> or = 1 in 10(4)) were selected. Twenty-nine strains of H. ducreyi were isolated recently from patients with chancroid and 50 A. actinomycetemcomitans strains from patients with periodontitis. The cytotoxic activity on HEp-2 cells and the presence of cdtABC genes were studied by cytotoxicity assay of bacterial sonicates and PCR with primers specific for individual cdtA, B, and C genes of H. ducreyi in bacterial DNA preparations, respectively. All strains that manifested a cytotoxic titre in sonicate > or = 1 in 100 possessed all the three cdt genes. Eighteen of the 50 strains selected from the culture collection were negative and 32 positive for cdt genes. As all strains with a high cytotoxic titre gave positive PCR results, it can be assumed that the remaining 50 strains, which have high cytotoxic titre, would have been positive as well. Thus, it can be estimated that 82% of the culture collection strains had cdtABC genes. Similarly, 24 (83%) of 29 recent H. ducreyi isolates expressed the CDT activity and displayed all cdtABC genes. Forty-three (86%) of 50 strains of the closely related A. actinomycetemcomitans, expressing a cytotoxic activity > or = 1 in 100, also possessed all three genes. Furthermore, the nucleotide sequence of the cdtABC genes was highly conserved among H. ducreyi strains from different geographic areas. These results indicate that the majority of pathogenic H. ducreyi and A. actinomycetemcomitans strains express a CDT activity encoded by all three cdtABC.