Corynebacterium amycolatum: An Emerging Pathogen in Chronic Otitis Media

Background: Corynebacterium amycolatum has traditionally been considered a commensal organism of the skin and mucosa; however, recent reports suggest its emerging role as a true pathogen in chronic otitis media (COM). Understanding its microbiological characteristics and resistance profile is essential for guiding effective antimicrobial therapy. Objectives: To describe the characteristics of C. amycolatum infection in patients with COM, evaluating its antibiotic susceptibility and resistance patterns. Materials and methods: A retrospective study was conducted on patients diagnosed with COM who had positive cultures for C. amycolatum between June 2022 and February 2025 at a secondary care center. Microbiological results, including susceptibility and resistance profiles, were analyzed using descriptive statistics. Results: During the study period, a total of 93 ear cultures were analyzed, of which 18 were positive for Corynebacterium species, including 12 cases of C. amycolatum. Eight had a single positive culture, while four had multiple positive cultures. C. amycolatum coexisted with other bacteria in eight cultures, 62% of which were coagulase-negative Staphylococcus. High resistance rates were observed for trimethoprim/sulfamethoxazole (100%), clindamycin (90%), levofloxacin (86.6%), and gentamicin (89%), while 100% susceptibility was noted for cefotaxime, cefepime, vancomycin, tetracycline, tigecycline, and linezolid. Conclusions: C. amycolatum is an emerging pathogen in COM, particularly in patients with cholesteatoma. There is also significant resistance to commonly used antibiotics, such as quinolones and penicillins. These findings highlight the need for accurate microbiological diagnosis and the implementation of targeted therapies to optimize treatment and prevent antimicrobial resistance.