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Journal of Clinical Microbiology, Oct 1995, 2647-2652, Vol 33, No. 10
A Pantosti, R Colangeli, AO Tzianabos and DL Kasper
The capsular polysaccharide complex (CPC) of Bacteroides fragilis is
composed of two distinct polysaccharides, designated PS A and PS B, and is
a major virulence factor of this microorganism. In order to investigate the
antigenic diversity of the CPCs of B. fragilis strains, we generated and
characterized 10 monoclonal antibodies (MAbs) directed to the CPCs of three
reference strains. The specificities of the MAbs were determined by
enzyme-linked immunosorbent assay and dot- immunobinding assay. At least
one MAb was specific for each PS A and PS B of the three strains. The MAbs
were used to detect capsular antigens on the surface of 231 B. fragilis
isolates from different geographical areas by a whole-cell
dot-immunobinding assay. Over half of the strains, regardless of the
country of origin, reacted with at least one MAb. Clinical extraintestinal
infection isolates were significantly more reactive than fecal isolates,
suggesting an association between capsular composition and the propensity
to cause clinical infections. The patterns of reactivity of the isolates
with the 10 MAbs were very different and sometimes extremely complex and
indicated a sharing of epitopes among different capsular polysaccharides.
The reactive strains could be grouped according to 32 different patterns;
some patterns were relatively common, while others were rarer and were
shown by only one or two strains. These results show that B. fragilis
capsular polysaccharides are antigenically extremely diverse. This
complexity and the large number of nonreactive strains indicate that a
typing system based on B. fragilis capsular antigens will be difficult to
establish.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Monoclonal antibodies to detect capsular diversity among Bacteroides fragilis isolates
Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanita, Rome, Italy.
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