Nocardia africana sp. nov., a new pathogen isolated from patients with pulmonary infections

Abstract

Eight actinomycete strains, isolated from 8 out of 400 sputum samples examined, taken from patients with pulmonary diseases at the Chest Unit of Khartoum Teaching Hospital in the Sudan, were provisionally assigned to the genus Nocardia according to morphological criteria. These isolates were studied further in order to establish their taxonomic status. They were found to have morphological and chemical properties typical of nocardiae and formed a monophyletic clade in the 16S ribosomal DNA tree together with Nocardia vaccinii. The strains showed a unique pattern of phenotypic properties that distinguished them from representatives of recognized Nocardia species, including Nocardia vaccinii. The strains were considered to merit species status and were designated Nocardia africana sp. nov. The findings of the present study are consistent with the view that pulmonary nocardiosis may occur in a substantial proportion of patients who exhibit chronic lung diseases in African countries. It is important, therefore, that clinicians in such countries consider this condition, especially when patients with respiratory infections fail to respond to antitubercular therapy.

FIG. 1

Neighbor-joining tree based on 16S rDNA sequences showing relationships between clinical isolates and other representatives of the genus Nocardia. The asterisks denote the branches that were also recovered by using the other algorithms, namely, the least-squares (9), maximum-likelihood (8), and maximum-parsimony (20) methods. The numbers at the nodes indicate the level of bootstrap support (%) based on a neighbor-joining analysis of 1,000 resampled data sets; only values above 50% are given. The scale bar indicates 0.1 substitution per nucleotide position. T, type strain.