# Chronic otorrhea and osteomyelitis of the external auditory canal by Achromobacter xylosoxidans: an uncommon diagnosis

## TL;DR

A rare case of ear infection caused by Achromobacter xylosoxidans led to bone infection in the ear canal, successfully treated with specific antibiotics.

## Contribution

This is the first reported case of osteomyelitis of the external auditory canal caused by Achromobacter xylosoxidans.

## Key findings

- Achromobacter xylosoxidans was identified as the cause of chronic otorrhea and osteomyelitis in a patient.
- Targeted antibiotic therapy with meropenem and cotrimoxazole resolved symptoms and prevented further bone erosion.
- Otic cultures are crucial for diagnosing atypical pathogens like Achromobacter xylosoxidans in chronic ear infections.

## Abstract

Achromobacter xylosoxidans is an emerging pathogen mainly associated with resistant nosocomial infections. This bacteria had been isolated in the ear together with other pathogens in cultures from patients with chronic otitis media, but it had never been reported as a cause of osteomyelitis of the external auditory canal.

We present a unique case of a healthy 81-year-old woman who presented with left chronic otorrhea refractory to topical and oral antibiotic treatment. Otomicroscopy revealed an erythematous and exudative external auditory canal (EAC) with scant otorrhea. The tympanic membrane was intact, but an area of bone remodeling with a small cavity anterior and inferior to the bony tympanic frame was observed. Otic culture isolated multi-drug-resistant A. xylosoxidans, only sensitive to meropenem and cotrimoxazole. Temporal bone computed tomography showed an excavation of the floor of the EAC compatible with osteomyelitis. Targeted antibiotherapy for 12 weeks was conducted, with subsequent resolution of symptoms and no progression of the bone erosion.

Atypical pathogens such as A. xylosoxidans can be the cause of chronic otitis externa. Early diagnosis and specific antibiotherapy can prevent the development of further complications, such as osteomyelitis. In these cases, otic cultures play an essential role to identify the causal germ. This is the first case of EAC osteomyelitis due to A. xylosoxidans reported to date.