NOCARDIA PSEUDOBRASILIENSIS SP-NOV, A NEW SPECIES OF NOCARDIA WHICH GROUPS BACTERIAL STRAINS PREVIOUSLY IDENTIFIED AS NOCARDIA-BRASILIENSISAND ASSOCIATED WITH INVASIVE DISEASES

We studied five strains of a new Nocardia taxon recently identified am ong Nocardia brasiliensis strains associated with invasive diseases (R . J. Wallace, Jr., B. A. Brown, Z. Blacklock, R. Ulrich, K. Jest, J. M . Brown, M. M. McNeil, G. Onyi, V. A. Steingrube, and J. Gibson, J. Cl in. Microbiol. 33:1528-1533, 1995) to determine their taxonomic status . Several characteristics of these organisms, including the presence o f chemotype IV cell walls, nocardomycolic acids, a predominant menaqui none similar to that of Nocardia asteroides ATCC 19247(T) (T = type st rain), and G+C contents ranging from 67 to 68 mol%, are characteristic s of the genus Nocardia. Phylogenies based on small-subunit ribosomal DNA sequences clearly confirmed that all five strains belong to the ge nus Nocardia and occur on a single branch that is clearly distinct fro m N. brasiliensis. This branch forms a clade with Nocardia vaccinii, N ocardia nova, Nocardia otitidiscaviarum, and Nocardia seriolae. The fi ve new strains exhibited high levels of DNA relatedness with each othe r, as determined by DNA DNA hybridization experiments (S1 nuclease pro cedure), but not with N, brasiliensis strains or with strains of the f our phylogenetically netically related Nocardia species mentioned abov e. The five new strains differ from N. brasiliensis in the following c haracteristics: mycolic acid pattern, decomposition of adenine, nitrat e reduction, and antimicrobial agent susceptibilities. Therefore, we p ropose that these strains belong to a new species, Nocardia pseudobras iliensis. The type strain is strain ATCC 51512, which was isolated fro m a leg abscess on a patient suffering from ulcerative colitis.