Bacteriological Profile of Chronic Suppurative Otitis Media and Antibiotic Susceptibility in a Tertiary Care Hospital in Shanghai, China

Abstract

Objective: Chronic suppurative otitis media (CSOM) is mostly caused by bacterial infection of the middle ear and antibiotics are generally used empirically, which may lead to the emergence of resistant bacterial strains. The objective of the study is to assess the bacteriological profile of and evaluate the antibiotic susceptibility of strains isolated in a tertiary care hospital in Shanghai, China. Methods: This study included 289 individuals with clinical diagnosis of CSOM. Middle ear purulent discharge was obtained with sterile swabs and cultured for bacterial pathogens. The susceptibility of the isolated microorganisms to antibiotics was assessed by a microdilution method. Results: Bacterial pathogens were found in 223 (77.2%) of the 289 cases. A total of 236 strains were isolated. Staphylococcus aureus was the commonest bacteria (44.9%) followed by Pseudomonas aeruginosa (16.9%) and coagulase-negative Staphylococcus (8.5%). There were 18.9% methicillin-resistant S aureus (MRSA) among the obtained S aureus organisms. Multidrug-resistant P aeruginosa was found in 4 patients, making up 10% of all detected P aeruginosa. Staphylococcus aureus showed highest susceptibility to vancomycin (100%), then gentamicin (98.1%) and rifampicin (97.2%) and was most resistant to penicillin (61.3%) and erythromycin (50%). All isolated P aeruginosa showed susceptibility to piperacillin, piperacillin/tazobactam, and meropenem. High degree of resistance in P aeruginosa was observed toward levofloxacin (42.5%), ciprofloxacin (40%), and ceftriaxone (30%). Conclusion: The high prevalence of MRSA and fluoroquinolone-resistant P aeruginosa indicated cephalosporins and fluoroquinolone as primary empirical antibiotic drugs in CSOM to be cautiously used. In order to reduce the incidence of resistant strains and promote effective usage of antibiotics, all aural discharges should be cultured to determine antibacterial susceptibility patterns before treatment.