Listeria tempestatis sp. nov. and Listeria rocourtiae subsp. hofi subsp. nov.

In September 2018, Hurricane Florence resulted in major flooding in North Carolina, USA. Efforts to isolate Listeria monocytogenes and other Listeria spp. from Hurricane Florence floodwaters repeatedly yielded non-haemolytic Listeria-like isolates that could not be readily assigned to known Listeria taxa. Whole-genome sequence analyses against the 28 currently known Listeria species confirmed that the isolates constitute two new taxa within the genus Listeria. Taxon I, with one isolate, showed the highest similarity to Listeria goaensis, with an average nucleotide identity blast of 85.3±4.4% and an in silico DNA-DNA hybridization (isDDH) of 32.4% (range: 30-35%), differing from the latter by its ability to reduce nitrate, ferment d-ribose and sucrose, and by its inability to produce catalase or ferment d-trehalose and d-lactose. Taxon II, represented by 11 isolates, showed the highest similarity to Listeria rocourtiae, with an average nucleotide identity blast of 92.64±3.8% and an isDDH of 49.9% (range: 47.3-52.5%), differing from the latter by its ability to ferment l-arabinose and its inability to ferment l-rhamnose, d-galactose, d-lactose and d-melibiose. The names Listeria tempestatis sp. nov. and Listeria rocourtiae subsp. hofi subsp. nov. are proposed for taxon I and II, respectively, with type strains CLIP 2022/01175^T (F6L-1A=CIP 112444^T = DSM 117029^T) and CLIP 2022/01000^T (F66L-1A=CIP 112443^T = DSM 117030^T), respectively. Both taxa lack known Listeria pathogenic islands, suggesting a lack of pathogenicity for humans.