Otitis media with effusion is a common disease entity in children, which is frequently managed surgically by insertion of a tympanostomy tube. Children who develop posttympanostomy tube otorrhea (PTTO) can be treated by administration of antibiotics. The abuse and misuse of antibiotics, however, has led to the emergence of resistant bacterial strains. We therefore examined the antibiotic sensitivity of bacterial strains collected from middle ear effusion fluid (MEEF) and PTTO. We also evaluated treatment outcomes in these patients. This study was conducted in 289 patients who underwent tympanostomy tube insertion for chronic otitis media with effusion between March 2004 and February 2008. Bacterial culture tests during the insertion of tympanostomy tubes showed a high frequency of coagulase(-) Staphylococcus (CNS), followed by Pseudomonas, methicillin resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA). Patients with PTTO had a high frequency of CNS and MRSA, followed by MSSA and Streptococcus pneumoniae. Overall antibiotic sensitivity was lower in postoperatively collected than in intraoperatively collected bacterial strains. The bacterial strains detected in MEEF, and their antibiotic sensitivity profiles, differed somewhat from those of PTTO. Antibiotic sensitivity was decreased in bacteria from PTTO compared with those in MEEF.