Listeria innocua

Listeria innocua is a species of Gram-positive rod-shaped bacteria. It is motile, facultatively anaerobic, and non-spore-forming. It was named innocua (innocuous) because as opposed to pathogenic Listeria monocytogenes, L. innocua was not found to be generally infectious.[1] Another Listeria species, L. seeligeri, was named after one of discoverers of L. innocua.

Listeria innocua
Scientific classification
Domain:	Bacteria
Phylum:	Firmicutes
Class:	Bacilli
Order:	Bacillales
Family:	Listeriaceae
Genus:	Listeria
Species:	L. innocua
Binomial name
Listeria innocua (ex Seeliger and Schoofs 1979) Seeliger 1983

L. innocua is almost always non-hemolytic, but a few strains have been found to be hemolytic.[2][3] Biochemically, L. innocua is very similar to L. monocytogenes. Exceptions for L. innocua include hemolysis (usually negative), arylamidase (positive), and phosphoinositide phospholipase C (negative).[4]

Although it is not generally considered a pathogen in terms of human health, Listeria innocua was identified in 2003 as the cause of a death of a 62-year-old, otherwise healthy, woman.[5]

As with other species in the genus, L. innocua occurs commonly in the environment (such as soil) and in food.[6] Strains of L. innocua have been shown to be able to form biofilms.[7] L. innocua has been tested and used as a laboratory surrogate for pathogenic L. monocytogenes in studies involving thermal, irradiation, and high-pressure processing of food.[8][9][10]

Knowledge of its specific structure has been refined during the 2000s, in particular to establish its distinction from Listeria monocytogenes.[11] L. innocua may inhibit detection of L. monocytogenes if both species are present.[12] One study found that L. monocytogenes was detected in 5.4% of inoculated beef broth samples when L. innocua was also present.[13]