Serological studies ofBacteroides fragilis

Abstract

SUMMARYUsing direct agglutination methods, a simple serological scheme for the classification of Bacteroides fragilis is described. Twenty strains of B. fragilis were selected by a process of successive screening from 151 strains obtained from various sources. 0-antigens were prepared from the 20 strains, and used to raise antisera in rabbits.Each of the 20 antisera reacted with its homologous antigen and eight antisera cross-reacted with other subspecies. These cross-reactions were successfully removed after absorption of the antisera with the cross-reacting antigens, resulting in 19 type-specific antisera, titres ranging from 40 to 320, and 19 distinct serotypes of B. fragilis. There was no correlation between the antigenic and the biochemical characteristics of these strains and no cross-reactions occurred with other gramnegative anaerobes, B. melaninogenicu8, Sphaerophorus necrophoruw and Fu8o-bacterium necrogenes.

A study of the surface and somatic antigens ofBacteroides fragilis

“…The results of testing 0-antigens against 0-antisera were similar to those obtained in our previous study (Elhag et al 1977). However, when whole-cell antigens were tested against these antisera, a number of reactions were lost and those remaining were present at low titres except serum 19 (Table 3).…”

“…Types 1-17 were the same as those used in a previous study (Elhag et al 1977). Two Peptone yeast broth (Cato et al 1970) was used for the production of B. fragilis antigens.…”

“…They were further identified by API 20A anaerobe system (Holdeman & Moore, 1972;Starr, Thompson, Dowell & Balows, 1973 0-antigens. These were prepared as previously described (Elhag et al 1977). …”

“…The serology ofBacteroidesfragilis was investigated by manyworkers and several serological classification schemes, based on the heat stable lipopolysaccharide (LPS), were proposed (Beerens, Wattre, Shinjo & Romond, 1971;Sharpe, 1971;Lambe & Moroz, 1976; Elhag, Bettelheim & Tabaqchali, 1977). However, the agglutination titres were always found to be low and cross-reactions of B. fragilis 0-antigens were frequently reported.…”

“…Using simple serological techniques, we set out to produce antisera against live cultures of B. fragilis and to compare their reactivity and specificity with those of 0-antisera previously prepared (Elhag et al 1977).…”