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Haemophilus ducreyi Outer membrane determinants, including DsrA, define two clonal populations
Catherine Dinitra White1, Isabelle Leduc, Bonnie Olsen
1Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA.
Infection and Immunity
|March 24, 2005
Summary
Two distinct classes of Haemophilus ducreyi were identified, differing in their outer membrane proteins and serum resistance. This discovery reveals two clonal populations within the H. ducreyi species.
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Haemophilus ducreyi outer membrane component DsrA is crucial for resistance to normal human serum (NHS).
- Previous studies characterized a prototypical strain (35000HP) expressing DsrA(I).
Purpose of the Study:
- To investigate the diversity of DsrA expression and outer membrane proteins in clinical isolates of H. ducreyi.
- To determine the role of different DsrA immunotypes in serum resistance and identify distinct H. ducreyi populations.
Main Methods:
- Western blotting was used to examine DsrA expression in 19 clinical isolates.
- Sequence analysis compared DsrA proteins from different strains.
- Functional assays assessed serum resistance after expressing variant DsrA in a mutant strain.
Main Results:
- Five of 19 H. ducreyi isolates expressed a distinct DsrA immunotype (DsrA(II)), differing significantly from DsrA(I).
- DsrA(II) strains also exhibited variant forms of other outer membrane proteins and distinct lipooligosaccharides, defining them as class II.
- DsrA(II) conferred significant serum resistance, similar to DsrA(I), confirming its critical role.
Conclusions:
- Two distinct clonal populations of H. ducreyi (class I and class II) exist, differentiated by key antigenic outer membrane components.
- These findings have implications for understanding H. ducreyi epidemiology and host-pathogen interactions.