Establishment of a chinchilla model of Achromobacter xylosoxidans-induced otitis media.

UNLABELLED: Achromobacter xylosoxidans (Ax) is an emerging opportunistic pathogen associated with chronic respiratory infections, particularly in individuals with cystic fibrosis; however, its role in otitis media (OM) and the mechanisms that underlie middle ear infection remain poorly defined. Despite its initial isolation from middle ear effusions decades ago, no experimental models of Ax-induced OM have been established. Here, we report the development of a reproducible chinchilla model of Ax-induced OM, which, to our knowledge, represents the first experimental model of Ax-induced middle ear infection. Following transbullar inoculation, two well-characterized clinical isolates established middle ear infection and induced measurable changes in tympanometry and otoscopic pathology. Notably, strain-specific differences in disease severity and persistence were observed, with one isolate inducing more pronounced inflammation, reduced tympanic membrane compliance, and prolonged bacterial survival within the middle ear mucosa. At the study endpoint, viable bacteria were recovered from a subset of infected ears despite resolution of overt clinical signs, which indicated a capacity for persistent mucosal infection. These findings demonstrate that Ax can establish and maintain infection within the middle ear and that clinical isolates exhibit distinct pathogenic phenotypes in this model. Together, this work establishes a reproducible and clinically relevant in vivo model for the study of Ax-induced OM and provides a foundation for future investigations into host-pathogen interactions, persistence mechanisms, and therapeutic interventions.

IMPORTANCE: Achromobacter xylosoxidans is an emerging opportunistic pathogen increasingly associated with chronic mucosal infection, yet its role in otitis media remains poorly defined. Mechanistic studies of middle ear infection have been limited by the absence of an experimental model. We establish the first reproducible animal model of A. xylosoxidans-induced otitis media and demonstrate that clinical isolates differ in their capacity to drive disease severity within the middle ear. By enabling controlled investigation of infection dynamics in vivo, this model provides a framework to define determinants of pathogenesis and directly compare strain-specific phenotypes across mucosal environments. These findings establish a foundation for future studies of A. xylosoxidans infection and therapeutic intervention.