title: The effect of temperature on the interaction of Haemophilus ducreyi with human epithelial cells.
abstract: To investigate if temperature affects the interaction of Haemophilus ducreyi with human epithelial cells, nine strains were used to evaluate the adhesion kinetics of the organism at 33 degrees C and 37 degrees C. The effect of the free toxin on the epithelial cells at those temperatures was also assessed. The cyto-adherence kinetics of H. ducreyi to the epithelial cells was significantly greater at 33 degrees C (10 times more) than at 37 degrees C in all seven clinical isolates tested. There was a significant difference in cell-associated H. ducreyi at 33 degrees C as compared with 37 degrees C. Control strains showed similar adhesion properties at both temperatures. However, the virulent strain CIP542 adhered in larger amounts than the avirulent strain A77. Electron microscopy revealed that there was more tissue necrosis at the lower than the higher temperature. The effect of the free toxin was the same at each temperature. However, strain A77 had significantly lower toxicity than strain CIP542 and the clinical isolates. These results suggest that H. ducreyi displays a temperature-dependent interaction with human epithelial cells, and this feature may play a role in the virulence of the organism in vivo. While the overall toxic effect of viable bacteria depends on the metabolic activity of the bacteria and is, therefore, higher at 33 degrees C than at 37 degrees C withthe same initial inoculum, the effect of the extracted toxin at molecular level with fixed concentrations is a temperature-independent event.
authors.affiliation: Department of Medical Microbiology and MRC Genital Ulcer Disease Research Unit, Faculty of Medicine, University of Natal, Durban, South Africa.
authors.forename: Sesupo C
authors.initials: SC
authors.lastname: Makakole
authors.affiliation: Department of Medical Microbiology and MRC Genital Ulcer Disease Research Unit, Faculty of Medicine, University of Natal, Durban, South Africa.
authors.forename: A Willem
authors.initials: AW
authors.lastname: Sturm
mesh_terms: D001422:Bacterial Adhesion; D002460:Cell Line; D006191:Haemophilus ducreyi / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000382:microbiology* / Q000648:ultrastructure; D007700:Kinetics; D008854:Microscopy, Electron; D013045:Species Specificity; D013696:Temperature; D013997:Time Factors