Ralstonia pickettii-induced ataxia in immunodeficient mice

Abstract

We report here the characterization of an asymmetric ataxia syndrome (head tilt and circling, with death in the most severe cases) demonstrated by profoundly immunodeficient mice housed at the Institut Curie SPF facility. The immune system of the affected mice had been genetically modified so that they were deficient in both B and T cells. Extensive bacteriologic, parasitic, serologic, and histopathologic analysis of the affected animals and their healthy controls led us to identify Ralstonia pickettii as the causative agent of the ataxic syndrome. The outbreak was managed through a test-and-cull process. Even though they also carried Ralstonia pickettii, immunocompetent mice that were kept in the same facility, did not show any of the signs that were expressed by their immunodeficient counterparts. This case highlights the difficulty of maintaining immunocompetent and immunodeficient mice in the same microbiologic unit and the importance of enlarging the spectrum of health monitoring to opportunistic agents when investigating clinical cases in populations of immunocompromised rodents.

Figure 1.

Photomicrographs of the (A through D) ear and (E) cerebrum of affected mice. (A) Suppurative otitis media, with the external ear canal obscured by inflammation (arrow). (B) Periosteal proliferation of bullae (arrow). (C) Ruptured thickened tympanic membrane (arrow). (D) Extra- and intracellular gram-negative bacilli. (E) Mild suppurative meningitis of the cerebrum. Haematoxylin–eosin–saffran (HES) stain (A through C, E); Gram stain (D). Scale bar: 500 µm (A through C); 20 µm (D); 50 µm (E).