Listeria monocytogenes
Researchers have found "Listeria monocytogenes" in at least 37 mammalian species, both domesticated and feral, as well as in at least 17 species of birds and possibly in some species of fish and shellfish. Laboratories can isolate "Listeria monocytogenes" from soil, silage, and other environmental sources. "Listeria monocytogenes" is quite hardy and resists the deleterious effects of freezing, drying, and heat remarkably well for a bacterium that does not form spores. Most "Listeria monocytogenes" strains are pathogenic to some degree.