The many faces of Raoultella spp.

Raoultella genus consists of Gram-negative, aerobic, encapsulated and non-motile rods. The name of the genus derives from the name of the French bacteriologist Raoul. Currently, four species belong to the genus: R. planticola, R. ornithinolytica, R. terrigena and R. elcctrica. The standard biochemical test used to identify Raoultella genus should be supplemented with additional tests, because of the close relationship between the genera Raoultella and Klebsiella. In 2001 Klebsiella planticola, K. ornithinolytica and K. terrigena were re-classified to new genus Raoultella. Re-classification was based on 16S rRNA sequence and rpoB, gyrA and gyrB genes. An alternative to phenotypic identification may be mass spectrometry or genetic methods (16s rRNA). These bacteria are commonly associated with natural environments (plants, water, soil). Raoultella spp. rods are not a highly virulent pathogen. Their virulence factors include polysaccharide capsule, fimbriae, siderophores, toxins and ability to form a biofilm. It has been shown that Raoultella spp. may colonize the gastrointestinal and upper respiratory tract in humans and cause cholangitis and lung infections. The literature also includes works on the antimicrobial activity of Raoultella rods and the possibility of using them in the environment protection. This review summarizes the current knowledge of Raoultella species identification, virulence and the possibility of using them in the protection of the environment.