Extended Numerical Taxonomy Study of Nocardia

Abstract

Numerical classification of 80 strains received as Nocardia using six different sets of characters was carried out. A set of 57 "differentiating" characters gave six distinct clusters: Nocardia farcinica, N . asteroides A, N . asteroides B, N . caviae, N. brasiliensis, and Gordona lentifragmenta (formerly, N . rubra) . Hence, the strains received as N. asteroides were divided into three subgroups, N . farcinica, N . asteroides A, and N . asteroides B. The cluster of G. lentifragmenta was placed apart from the others, and a previous classification of this taxon as a species of Gordona was supported by the present study. The problem of a minimum number of differentiating characters necessary for numerical classification, which was considered theoretically as above 40 or 50, was studied experimentally in this study. The results supported the theoretical considerations. Inclusion of linked characters reduced the number of clusters.Previous studies on the taxonomy of Nocardia were made by Gordon and Mihm (6-9) by use of physiological and biochemical characters. Many species were merged into a few species. Gordon and Mihm (6, 8) included the strain ATCC 3318, labeled as Nocardia farcinica, in the species Nocardia asteroides. The first numerical classification of Nocardia was carried out by Cerbon (3). He suggested that the species N . asteroides be divided into several subgroups. Subsequently, Tsukamura (22) carried out a numerical classification of Nocardia using a large number of characters and reported that the strains received as N . asteroides were divided into two distinct taxa. In this study, the strain ATCC 3318 of N . farcinica was included in one cluster. Hence, this cluster was named N . farcinica and another cluster was designated N. asteroides. These two taxa could be differentiated by several characters. The former grew at 45"C, showed acetamidase and benzamidase activities, formed acid from rhamnose, and utilized 1,3-butylene glycol as sole carbon source and acetamide and monoethanolamine as simultaneous nitrogen and carbon sources; the latter taxon did not. This finding was supported by Berd ( l ) , Holm (lo), and Franklin and McClung (4) by use of the same phenetic analysis, and by Bradley (2) and Franklin and McClung (4) by use of a deoxyribonucleic acid hybridization technique. Magnusson and Mariat (14) suggested that, by using a delayed type skin reaction, M. farcinica be separated from N. asteroides.At a later date, Goodfellow (5) and Kurup and Schmitt (11) reported that the species N . asteroides is divided into five and four subgroups, respectively. Goodfellow used none of the same strains as used by Tsukamura (22), and Kurup and Schmitt stated that one of their subgroups was identical to Tsukamura's N . farcinica.The present study was carried out for two reasons: (i) to reinvestigate the heterogeneity of N. asteroides by use of a new set of characters which included several characters not used previously, and (ii) to observe the relationship between the clustering and the characters used in the...

Taxonomic Studies on the Mycobacterium tuberculosis Series

“…Since test strains were restricted to slowly growing mycobacteria, characters useful only for differentiating among rapidly growing mycobacteria were omitted. It was shown previously that the inclusion of linked characters reduces the number of clusters (21). Therefore, characters considered as linked were not used whenever possible.…”

The medically important aerobic actinomycetes: epidemiology and microbiology

“…However, this identification method does not differentiate the N. asteroides complex from the nonpathogenic Nocardia species Nocardia camea, Nocardia amarae, and Nocardia brevicatena or from species of the related genera Mycobacterium, Rhodococcus, Gordona, and Tsukamurella. In the past, the use of these few biochemical tests and morphology alone resulted in the genus Nocardia being characterized by extreme heterogeneity (196,201,203,335,512,598). In particular, the consistency and composition of the growth medium can affect the growth and stability of both aerial and substrate hyphae.…”

“…infections. The heterogeneity within the species N. asteroides has been well documented by numerical phenetic (196,204,431,512,596,598), genetic (174,402), and immunologic (365,449,472) (518). Also, as suggested for N. farcinica infections, infections with N. nova may be more common than is presently suspected; however, the successful detection of these newly recognized species of microorganisms is dependent upon the performance of appropriate isolation and characterization techniques (621 (510).…”

Nocardia farcinica as a Pathogen of Lung Infection

“…, and Tsukamura (19) in numerical phenetic analysis. All of these investigators supported the distinctness of the N. farcinica cluster (or Tsukamura's Kyoto-I group).…”

“…The methods of identification were described previously (19). Two reference strains were used, strain 23102 (ATCC 3318) offarcinica and strain 23094 (R-399, ATCC 23824) of N. asteroides in senso stricto.…”