[Immunologic identification of Streptococcus mutans using microimmunodiffusion and counterimmunoelectrophoresis...

The St. mutans strains studied were: HS6 "a"; BHT "b"; IB "c"; B13 "d"; LM7 "e"; OMZ175 "f"; OMZ65 "g"; SL1 "SL"; 6715 "d/g". Immune sera and antigen preparation as well as antigen-antibody reactions were performed using the above-mentioned strains. The immune sera were obtained following Knox technique, including formolated immunogen with and without adjuvant. Linzer method was followed for rabbit immunization. The antigen extract were prepared according to Rantz and Randall method. The antigen-antibody reaction were carried out by microimmunodiffusion (MID) Ouchterlony technique and by counterimmunoelectrophoresis (CIE) according to De Torres method. A good correlation was found in the antigen-antibody reactions for the serotypes studied. MID and CIE revealed some cross-reactions, as already described by many investigators. The results obtained are compatible with St. mutans antigenic instability. The eight serotypes from St. mutans could possibly be reduced to four related groups: Group 1: serotypes "a-d-g-SL"; Group 2: serotype "e-f"; Group 3: serotype "c" (uncertain position: it can be related with group 1 or 2); Group 4: serotype "b". CIE is a convenient technique to be incorporated for immunological determination.