Review of otorrhea microbiology: is there a pathogenic role of corynebacter?

OBJECTIVE: Identification of a causative pathogen in otologic infections assists in maximizing therapy efficacy particularly in refractory and chronic cases. Current standards for treatment of otologic infections focus on targeted species (spp.) that are assumed to be the most common pathogens. Corynebacterium spp. may play a pathogenic role but are not routinely speciated or included in antibiotic susceptibility analysis. Our objective is to investigate the prevalence and pathogenicity of nondiphtheroid Corynebacterium spp. in commonly encountered purulent and mucopurulent otologic infections.

STUDY DESIGN: Retrospective case review.

SETTING: Academic tertiary referral center.

PATIENTS: Review of 140 microbiology cultures from adults and children presenting with purulent and mucopurulent otologic infections from 2010 to 2012.

INTERVENTION(S): Clinical history, demographics, and microbiology cultures with speciation and antibiotic susceptibility analyses.

MAIN OUTCOME MEASURE(S): Microbiologic speciation and census, species association with clinical characteristics, antibiotic susceptibility to oral and systemic agents, therapy frequency and agent selection.

RESULTS: Corynebacterium spp. was the second most common bacteria isolated from patients with clinically significant otologic infections. Corynebacterium spp. were found in 24 (33.3%) unique patients with otologic infections and were the only pathogen isolated in six (8.33%) patients. Corynebacterium-positive infections were significantly associated with the use of hearing aids, a diagnosis of chronic granular myringitis, and less otalgia. Corynebacterium isolates were highly resistant to first-line fluoroquinolone therapy. The majority of patients with Corynebacterium-positive infections harbored at least one resistant strain, and patients with strains resistant to first-line topical therapy had a nonsignificant trend to an alteration in antibiotic therapy after antibiotic susceptibility data became available.

CONCLUSION: Corynebacterium spp. may be underestimated in their potential to cause clinically significant otologic infections. Our results indicate a potential need for expanding surveillance for Corynebacterium spp.