Low virulence but potentially fatal outcome-Listeria ivanovii.

Of the six known species of Listeria, Listeria monocytogenes is classified as the only human pathogen causing listeriosis, a highly fatal, opportunistic infection contracted via food. Listeria ivanovii is the only other pathogenic species of the genus and is considered to be specific to ruminants, except for extremely rare cases of infection in humans. We report here on a 64-year-old male patient with L. ivanovii who responded favorably to treatment with intravenous ampicillin.