RESUMEN
Fifty patients , 7 to 52 years of age, with chromic otitis media with mastoiditis and treated with radical mastoidectomy , at Srinagarind Hospital, KhonKaen University were studied. The pus swabs from mastoid antrums were cultured and identified for bacterial and fungal infection. Forty five specimens (90%) were found the bacterial growth on the cultures but no growth appeared on fungal cultivation. The bacteria isolated were aerobes, anaerobes and mixed organisms in the percentage of 53.33 , 8.89 and 37.78 respectively. The gram negative bacilli found in aerobic group were-proteus mirabillis (30.0%) Pseudomonas aeruginosa (21.42%) Providencia rettgeri (4.29%) , Klebsiella species (1.43%) Enterobacter species (1.43%) Acinetobacter calcoaceticus var anitratus (1.43%) and the gram positive cocci were enterococci (7.14%) Staphylococcus aureus (1.43%) and alpha streptococci (1.43%). The bacteria found in anaerobic group were Peptostreptococcus specis (14.29%) , Clostridium (4.29%) Bacteroides melaninogenicus (4.29%) Bacteroides species (2.86%) B.fragills (1.43%) Fusobacterium species (1.43%) and Peptococcus species (1.43%) The predominant bacteria, proteus mirabillis and Pseudomonas aeruginosa isolates, were susceptible to gentamicin in the percentage of 94.74 and 100, respectively. P.mirabillsisolates were also sensitive to trimethoprim / sulfamethoxazole (88.24%) and cepholothin (80%) and Ps.aeruginosa isolates were also susceptible to tobramycin (100%) and polymyxin (90%)