Cytotoxin production in 100 strains of Haemophilus ducreyi from different geographic locations

M Purven, E Falsen, T Lagergård - FEMS microbiology letters, 1995 - academic.oup.com
M Purven, E Falsen, T Lagergård
FEMS microbiology letters, 1995academic.oup.com
One-hundred strains of Haemophilus ducreyi, representing isolates from different parts of
the world, including the reference strains, were obtained from different collections and
characterized with special reference to cytotoxin production in vitro. The cytotoxic activity on
cultured epithelial cells (HEp-2) was examined with two methods. The activity in bacterial
sonicates was tested on freshly trypsinated cells and strains manifesting little or no cytotoxic
activity in sonicates were investigated using attached living bacteria on HEp-2 cell …
Abstract
One-hundred strains of Haemophilus ducreyi, representing isolates from different parts of the world, including the reference strains, were obtained from different collections and characterized with special reference to cytotoxin production in vitro. The cytotoxic activity on cultured epithelial cells (HEp-2) was examined with two methods. The activity in bacterial sonicates was tested on freshly trypsinated cells and strains manifesting little or no cytotoxic activity in sonicates were investigated using attached living bacteria on HEp-2 cell-monolayers. Sonicates from the majority of the H. ducreyi strains (89%) produced significant cytotoxic effects on HEp-2 cells. The reciprocal cytotoxic titers of the sonicates ranged from 2.4 × 102 to 5.3 × 105. Sonicates of 11 strains had low cytotoxic titers (≤ 1:3 to 1:81), eight of those originating from Asia and three from Africa. These 11 strains caused no damage to the cell monolayer, indicating that the 11 strains produce little or no cytotoxic activity in vitro. In summary, the majority of H. ducreyi isolates produce cytotoxic activity, which support the hypothesis that the cytotoxin may be an important virulence factor of this species.
Oxford University Press