Klebsiella oxytoca as an unusual agent of mixed diffuse otitis externa: Case report and literature review

Abstract

Introduction: Diffuse otitis externa is an acute inflammation of the external auditory canal, most commonly caused by Pseudomonas aeruginosa and Staphylococcus aureus. The involvement of other gram-negative bacilli is exceptional and poorly documented. Objective: This report aims to contribute evidence through the description of a case of diffuse otitis externa in which Klebsiella oxytoca was isolated, a bacterium not previously described as a causal agent of human otic infections, and to highlight the clinical relevance of considering unusual pathogens in cases with atypical clinical courses. Methodology: We present the case of a 43-year-old man with clinical features of mixed otitis externa, whose culture showed growth of Klebsiella oxytoca and Aspergillus niger. The patient was evaluated clinically and by otomicroscopy, with microbiological sampling and follow-up after targeted topical treatment. Result: The patient evolved favorably under topical antifungal and antibacterial therapy. Discussion: Klebsiella oxytoca is an opportunistic gram-negative bacillus whose role in otitis has only been reported in animal models and in a single human case of malignant otitis externa in 1992, with no subsequent reports in the literature. In this case, clindamycin-induced dysbiosis and local immunosuppression due to topical corticosteroids likely favored its occurrence. Conclusion: This report documents a case of diffuse otitis externa associated with Klebsiella oxytoca and Aspergillus niger, highlighting the importance of considering unusual pathogens and performing cultures with antibiograms in cases of atypical evolution, reinforcing the need for a clinical approach based on critical thinking and diagnostic reassessment when facing non-standard presentations.