Experimental otitis media in guinea pigs. Serum antibody response to Bacteroides fragilis, Propionibacterium acnes and Peptostreptococcus anaerobius upon challenge.

The production of antibodies in serum was studied after inoculation of Bacteroides fragilis, Propionibacterium acnes or Peptostreptococcus anaerobius into the middle ear of guinea pigs. Inoculation of B. fragilis resulted in IgG and IgM serum antibodies at an early stage of the infection, while IgA antibodies were seldom detected and at a later stage. In contrast, inoculation of P. acnes or P. anaerobius induced no serum antibody response. Of these three species B. fragilis induced the most intense otitis, whereas P. anaerobius failed to induce otitis.