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  • 1
    In: Infection and Immunity, 2000, Vol. 68(11), p.6441
    Description: Haemophilus ducreyi expresses a peptidoglycan-associated lipoprotein (PAL) that exhibits extensive homology to Haemophilus influenzae protein 6. We constructed an isogenic PAL mutant (35000HP-SMS4) by the use of a suicide vector that contains lacZ as a counterselectable marker. H. ducreyi 35000HP-SMS4 and its parent, 35000HP, had similar growth rates in broth and similar lipooligosaccharide profiles. 35000HP-SMS4 formed smaller, more transparent colonies than 35000HP and, unlike its parent, was hypersensitive to antibiotics. Complementation of the mutant in trans restored the parental phenotypes. To test whether expression of PAL is required for virulence, nine human volunteers were experimentally infected. Each subject was inoculated with two doses (41 to 89 CFU) of live 35000HP and one dose of heat-killed bacteria on one arm and with three doses (ranging from 28 to 800 CFU) of live 35000HP-SMS4 on the other arm. Papules developed at similar rates at sites inoculated with the mutant or parent but were significantly smaller at mutant-inoculated sites than at parent-inoculated sites. The pustule formation rate was 72% (95% confidence interval [CI], 46.5 to 90.3%) at 18 parent sites and 11% (95% CI, 2.4 to 29.2%) at 27 mutant sites (P 〈 0.0001). The rates of recovery of H. ducreyi from surface cultures were 8% (n = 130; 95% CI, 4.3 to 14.6%) for parent-inoculated sites and 0% (n = 120; 95% CI, 0.0 to 2.5%) for mutant-inoculated sites (P 〈 0.001). H. ducreyi was recovered from six of seven biopsied parent-inoculated sites and from one of three biopsied mutant-inoculated sites. Confocal microscopy confirmed that the bacteria present in a mutant inoculation site pustule lacked a PAL-specific epitope. Although biosafety regulations precluded our testing the complemented mutant in humans, these results suggest that expression of PAL facilitates the ability of H. ducreyi to progress to the pustular stage of disease.
    Keywords: Bacterial Outer Membrane Proteins ; Proteoglycans ; Haemophilus Infections -- Etiology ; Haemophilus Ducreyi -- Pathogenicity ; Lipoproteins -- Metabolism ; Peptidoglycan -- Metabolism;
    ISSN: 0019-9567
    ISSN: 00199567
    E-ISSN: 10985522
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  • 2
    Language: English
    In: Microbial Pathogenesis, February 1999, Vol.26(2), pp.93-102
    Description: A bactericidal assay was developed in order to test the effect of hyperimmune rabbit sera on the viability of serum-resistant Haemophilus ducreyi 35000HP. Testing of several lots of rabbit complement and time course experiments showed that the serum-sensitive H. ducreyi CIPA77 was killed efficiently by 25% complement at 35°C in 3 h. We hypothesized that incubation of 35000HP under these conditions with the appropriate bactericidal antibody would kill this strain. A panel of high titre rabbit antisera was developed and tested against 35000HP. The panel included antisera raised to whole cells, total membranes, Sarkosyl-insoluble outer membrane proteins, the H. ducreyi lipoprotein, and the peptidoglycan-associated lipoprotein. None of the antisera convincingly showed bactericidal activity. The bactericidal assay was also used to determine the effect of normal human serum (NHS) on isogenic mutants of 35000HP. 35000HP-RSM2, an kan insertion mutant that expresses a truncated lipooligosaccharide, was as resistant to NHS as its parent. A mutant deficient in expression of the major outer membrane protein (35000.60) was sensitive to NHS. We conclude that 35000HP is relatively resistant to normal and hyperimmune sera, and that the major outer membrane protein contributes to this resistance. Copyright 1999 Academic Press
    Keywords: Haemophilus Ducreyi, Bactericidal Activity, Chancroid ; Biology ; Chemistry
    ISSN: 0882-4010
    E-ISSN: 1096-1208
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