''Listeria innocua'' is a species of

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacte ...

rod-shaped A bacillus (), also called a bacilliform bacterium or often just a rod (when the context makes the sense clear), is a rod-shaped bacterium or archaeon. Bacilli are found in many different taxonomic groups of bacteria. However, the name ''Bacillu ...

bacteria. It is

motile Motility is the ability of an organism to move independently, using metabolic energy. Definitions Motility, the ability of an organism to move independently, using metabolic energy, can be contrasted with sessility, the state of organisms th ...

, facultatively anaerobic, and non-

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

-forming. ''L. innocua'' was named ''innocua'' (innocuous) because, in contrast to ''

Listeria monocytogenes ''Listeria monocytogenes'' is the species of pathogenic bacteria that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. It can grow and reproduce inside the host' ...

'', it does not readily cause disease in

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s. Another ''

Listeria ''Listeria'' is a genus of bacteria that acts as an intracellular parasite in mammals. Until 1992, 17 species were known, each containing two subspecies. By 2020, 21 species had been identified. The genus is named in honour of the British pi ...

'' species, '' L. seeligeri'', was named after one of the discoverers of ''L. innocua''. Biochemically, ''L. innocua'' is very similar to ''L. monocytogenes'', except that ''L. innocua'' is usually non-hemolytic, arylamidase-positive, and

phosphoinositide phospholipase C Phosphoinositide phospholipase C (PLC, EC 3.1.4.11, triphosphoinositide phosphodiesterase, phosphoinositidase C, 1-phosphatidylinositol-4,5-bisphosphate phosphodiesterase, monophosphatidylinositol phosphodiesterase, phosphatidylinositol phosph ...

-negative. Although it is not generally considered a human pathogen, ''L. innocua'' was identified in 2003 as the cause of death of a 62-year-old, otherwise healthy, woman. As with other species in the genus, ''L. innocua'' occurs commonly in the environment (such as soil) and in food. Strains of ''L. innocua'' have been shown to be able to form

biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...

s. ''L. innocua'' has been tested and used as a laboratory surrogate for pathogenic ''L. monocytogenes'' in studies involving

thermal A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...

irradiation Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve ...

, and high-pressure processing of food. Knowledge of the structure of ''L. innocua'' was refined during the 2000s to help distinguish it from ''L. monocytogenes''. ''L. innocua'' may inhibit detection of ''L. monocytogenes'' if both species are present. One study found that ''L. monocytogenes'' was detected in 5.4% of inoculated beef broth samples when ''L. innocua'' was also present.

References

{{Taxonbar, from=Q3834922 innocua