Phytobacter

Phytobacter is a genus of Gram-negative bacteria emerging from the grouping of isolates previously assigned to various genera of the family Enterobacteriaceae. This genus was first established on the basis of nitrogen fixing isolates from wild rice in China,[1] but also includes a number of isolates obtained during a 2013 multi-state sepsis outbreak in Brazil [2][3] and, retrospectively, several clinical strains isolated in the 1970s in the United States that are still available in culture collections, which originally were grouped into Brenner's biotype XII.[4][5] Standard biochemical evaluation panels are lacking Phytobacter spp. from their database, thus often leading to misidentifications with other Enterobacterales species, especially Pantoea agglomerans.[2] Clinical isolates of the species have been identified as an important source of extended-spectrum β-lactamase and carbapenem-resistance genes, which are usually mediated by genetic mobile elements. Strong protection of co-infecting sensitive bacteria has also been reported.[6] Bacteria belonging to this genus are not pigmented, chemoorganotrophic and able to fix nitrogen. They are lactose fermenting, cytochrome-oxidase negative and catalase positive. Glucose is fermented with the production of gas. Colonies growing on MacConkey agar (MAC) are circular, convex and smooth with non-entire margins and an usually elevated center. Three species are currently validly included in the genus Phytobacter,[2][7] which is still included within the Kosakonia clade in the lately reviewed family of Enterobacteriaceae.[8] The incorporation of a fourth species, Phytobacter massiliensis, has recently been proposed via the unification of the genera Metakosakonia and Phytobacter.[9]

Colonies of P. diazotrophicus on MacConkey agar.