The association of particular types of Proteus with chronic suppurative otitis media.

During a period of 12 months, 57 strains of Proteus were isolated from the ears of 38 unrelated patients with chronic suppurative otitis media. Each strain was identified, typed for bacteriocin production and sensitivity, and tested for Dienes compatibility. The majority of the strains (79%) were P. mirabilis; all but one of the remainder were P.vulgaris. Although 19 different bacteriocin production/sensitivity types were found, two rare types, P. mirabilis P7/S5,12 and P. vulgaris P0/S9, were associated with 47% of these infections. This was confirmed by Dienes typing. Patients with bilateral ear disease carried a different strain in each ear. There was no evidence that persistence of infection had arisen because of the development of antibiotic resistance. Although there was some evidence that persistence may have been the result of reinfection, the isolation of these rare types of Proteus from so many patients with chronic suppurative otitis media may indicate that they play an important role in the pathogenesis of the disease. Most of the Proteus isolates were of "non-faecal" types and it is believed that infection had arisen by a route other than the faecal-aural one.