A GERBIL MODEL FOR RHOMBENCEPHALITIS DUE TO LISTERIA-MONOCYTOGENES

Rhombencephalitis due to Listeria monocytogenes is a frequent complica tion of human listeriosis, inducing a high mortality and severe neurol ogical sequelae despite antibiotic therapy. However, there is no anima l model which consistently reproduces clinical rhombencephalitis. Here , we present a model of Listeria rhombencephalitis in gerbils. Animals were inoculated in the middle ears with a low infective dose of L. mo nocytogenes, thus creating prolonged otitis media with persistent bact eremia. Gerbils developed a severe rhombencephalitis with circling syn drome, paresia, ataxia, rolling movements. The invasion of the central nervous system was visualized on living animals by resonance magnetic imaging and characterized by bacterial growth in the brain, reaching about 10(7) bacteria in the rhombencephalum by day 12 of infection. Th e histological lesions were mainly located in the brainstem, and consi sted in coalescent, necrotic abscesses with perivascular sheaths, mimi cking those observed in human rhombencephalitis. Bacteria were detecte d by electronmicroscopy inside infectious foci, either free in necroti c material or inside inflammatory cells, mainly polymorphonuclear cell s. This gerbil model of Listeria rhombencephalitis will be useful to s tudy the molecular mechanisms allowing bacteria to cross the blood-bra in barrier, and to evaluate the intracerebral efficacy of antibiotics. (C) 1997 Academic Press Limited.