Antagonism among Bacteroides fragilis group strains isolated from middle ear exudates from patients with chronic suppurative otitis media.

The production and sensitivity of a bacteriocin-like substance in Bacteroides fragilis group strains isolated from middle ear exudates in children with suppurative otitis media were studied through antagonism assayed by the well method. The results of the crossed reactions showed that 10 strains (66.6%) were bacteriocinogenic, 9 were sensitive to at least 1 bacteriocin (60%), and none showed inhibitory activity against homologous strains. Different patterns of susceptibility to bacteriocin-like substances were observed among strains isolated from the same patient as well as different strains isolated from another patient. These findings indicate that bacteriocin typing of anaerobic bacteria isolated from middle ear exudates in children with otitis media might have use in epidemiologic studies.