Comparison of bacteria in the tympanic cavity and the mastoid antrum in chronic otitis media.

Materials collected from the tympanic cavity before operation and from the mastoid antrum during operation of 58 discharging ears of patients with chronic otitis media were cultured, and the bacteria in these two cavities were compared. Staphylococcus aureus was the commonest organism in the tympanic cavity, and S epidermidis in the mastoid antrum. Anaerobic bacteria were found only in the mastoid antrum of patient with cholesteatoma. In 32 (55 per cent) of the 58 ears examined, bacteria were detected in both the tympanic and mastoid cavities. In 17 ears (53 per cent), the bacterial strains in the two cavities differed. The results indicate the necessity of bacteriologic examination of the mastoid cavity during operation to select antibiotics for postoperative treatment.