Background & Objective: Chronic otitis media infection exists among 1.5-2 percent of people and its purulent discharges can create some difficulties for the patients. Chronic otitis media is mainly due to pseudomonas aeruginosa and staphylococcus aurous. Severe and irreversible damages should be expected unless follow up treatments are exactly performed in such patients. This study was conducted to determine the most prevalent microorganisms involved in otitis infection and their sensitivity to antibiotics.

 Methods: This is a descriptive study in which 60 patients who referred to nose and throat clinics of Ardabil University of Medical Sciences (2000-2001) were selected. Using applicator, some samples were taken from suppurative discharges of middle ear. These samples were then cultured in lactose broth and Nutrient broth. In order to isolate pathogenic microorganism, samples were also cultured in blood agar. Sensitivity of isolated pathogenic microorganism was determined against some antibiotics. The data obtained were analyzed using SPSS software.

 Results: 56 out of 60 patients were culture positive. Microorganisms isolated from suppurative otitis media were Staphylococcus areus (31.6%), pseudomonas aeuroginosa (26.6%), proteus (20%), candida albicans (6.4%), Staphylococcus epidermidis (4.6%), aeuromonas (1.6%) and others (6.4%) respectively. Sensitivity of microorganisms to antibiotics was found to be Ciprofloxacin (94.6%), Co-trimoxazole (66.3%), Cloxacilin (64.3%), Chloramphenicol (64.3%),Cephalexin (64.3%), Erythromycin (60.7%), Amikacin (44.6%), Streptomycin (39.3%), Penicillin (5.4%) respectively.

 Conclusions: Since staphylococcus areus was�the most prevalent micro-organism in otitis media infection, and isolated microorganisms were more sensitive to Ciprofloxacin, antibiogram test is necessary prior to the treatment of otitis media.