Human Listeriosis Caused by Listeria ivanovii

International audience; Two species of Listeria are pathogenic; L. monocytogenes infects humans and animals, and L. ivanovii has been considered to infect ruminants only. We report L. ivanovii–associated gastroenteritis and bacteremia in a man. This isolate was indistinguishable from prototypic ruminant strains. L. ivanovii is thus an enteric opportunistic human pathogen.The genus Listeria contains 2 pathogenic species, L. monocytogenes and L. ivanovii (1). They both invade host cells, replicate in the cytosol after phagosomal escape, and spread from cell to cell by polymerizing actin. These mechanisms correlate with the presence in each species of genetic determinants called the inlAB internalization locus, the LIPI-1 intracellular survival pathogenicity island, and the hpt intracellular growth locus (2). However, each species appears to infect different hosts: L. monocytogenes infects humans and ruminants, whereas L. ivanovii is thought to infect ruminants only (2). L. ivanovii have been previously isolated, although rarely, from infected humans, indicating pathogenic potential for humans (Table). We report a case of L. ivanovii infection in a man with a kidney transplant. The ecology of L. ivanovii suggests that the rarity of human listeriosis due to this species reflects not only host tropism factors but also the rare occurrence of this species in the environment, compared with L. monocytogenes.