Six ‘Bacteroides fragilis’ serotype‐specific fluorescein‐labelled antisera were prepared and used in the direct immunofluorescence test (IFT). The method permitted the rapid detection of serotypes within the ‘B. fragilis’ group. The specificity is connected with the phenol‐water extracted endotoxins.
Material from 32 patients, mostly after abdominal surgery, was examined by the direct immunofluorescence test (IFT) using the conjugates against six ‘Bacteroides fragilis’ serotypes. In most cases ‘B. fragilis’ strains could be detected in direct smears of the clinical material. There was good agreement between the results obtained by IFT and cultural methods.
Antigens were extracted by the phenol‐water method from each of the 11 strains of ‘Bacteroides fragilis’ species, isolated from clinical material. Nine of these strains had been identified by the direct immunofluorescence test (IFT) as ‘B. fragilis spp. fragilis’, and two as ‘B. fragilis ssp. thetaiotaomicrori’.
These antigens were then used in the immunodiffusion test (ID), performed with antisera of six serotypes. Results of the ID test agreed in nine cases with those of IFT. An antigenic heterogeneity among strains of ‘B. fragilis ssp. fragilis’ strains was noted. Antigens prepared in the same way from two strains did not react in the ID test with any of the antisera used although cells were positively stained in the IFT by specific anti‐‘B. fragilis’ serotype conjugates.
Culture supernatants of 17 strains of the ‘Bacteroides fragilis’ group were treated with four volumes of acetone. The precipitates, after dialysis and lyophilization, were used as antigens in the double diffusion test with antisera against serotype strains of ‘B. fragilis’. In the culture supernatant of one strain we did not demonstrate the presence of serologically active substances. Sixteen preparations reacted in immunodiffusion with antiserum against ‘B. ovatus’ serotype B. Ten preparations reacted with antiserum B only and six preparations gave, additionally, precipitation lines with other serotype antisera (A, E2).
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