Summary auto-generated
Researchers identified a novel Nocardia species isolated from bronchoscopic lavage of a 78-year-old patient with a history of tuberculous pleurisy who presented with bilateral upper lobe lesions. The aerobic, Gram-positive bacterium produced beige substrate mycelium and scant white aerial mycelium. Comprehensive analysis using morphological, physiological, chemotaxonomic, and molecular methods confirmed its classification within the genus Nocardia. The strain possessed diagnostic characteristics including meso-diaminopimelic acid in peptidoglycan, specific cell wall sugars (arabinose and galactose), a Nocardia-specific menaquinone (MK-8), and mycolic acids with 54-62 carbon atoms. Phylogenetic analysis of 16S rRNA sequences showed highest similarity to Nocardia vaccinii at 98.6%, but DNA-DNA reassociation analysis revealed only 31% similarity, confirming species-level distinction. The isolate demonstrated a unique physiological profile, utilizing different carbon sources than N. vaccinii. Based on these integrated data, the authors propose the name Nocardia veterana sp. nov. for strain M157222T, designated as type strain DSM 44445T. Though initially considered clinically insignificant, this work establishes a new recognized species within the medically important Nocardia genus.
Key findings
- A novel Nocardia species, N. veterana, was isolated from human bronchial lavage and characterized using polyphasic taxonomy combining morphology, physiology, chemotaxonomy, and molecular analysis
- Phylogenetic analysis showed N. veterana is most closely related to N. vaccinii (98.6% 16S rRNA similarity) but represents a distinct species with only 31% DNA-DNA relatedness
- The strain exhibits distinctive physiological traits in carbon source utilization that differentiate it from its closest phylogenetic neighbor N. vaccinii
- Chemotaxonomic analysis confirmed classification within Nocardia through characteristic mycolic acids (C56, C58, C60), menaquinone composition, and polar lipid patterns
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Abstract
A nocardioform bacterium was isolated from the bronchoscopic lavage of a 78-year-old man with a past history of tuberculous pleurisy, who presented with bilateral upper lobe lesions at Austin and Repatriation Medical Centre, Heidelberg, Australia. The strain was aerobic, Gram-positive, produced beige substrate mycelium and scant white aerial mycelium. It showed chemotaxonomic markers which were consistent with the classification of Nocardia: i.e. meso-diaminopimelic acid, N-glycolylmuramic acid, arabinose and galactose as diagnostic sugars; phospholipids phosphatidylinositol mannosides, phosphatidylinositol, phosphatidylethanolamine and diphosphatidylglycerol; a menaquinone with a cyclic isoprene side chain, MK-8(H(4cycl.)); a fatty acid pattern composed of unbranched saturated and monounsaturated fatty acids with a considerable amount of tuberculostearic acid; and mycolic acids composed of 54--62 carbon atoms with three principal mycolic acids which were mono- and polyunsaturated, showing a chain length C(56), C(58) and C(60) and accounting for over 70% of the entire pattern. The 16S rDNA sequence showed the highest similarity to the type strain of Nocardia vaccinii; the DNA--DNA similarity of the two strains was 31%. These data, together with distinct physiological traits and molecular biological analyses, as well as chemotaxonomic results, led to the conclusion that the novel isolate represents a new species within the genus Nocardia for which the name Nocardia veterana sp. nov. is proposed. The type strain is M157222(T) (DSM 44445(T)=NRRL B-24136(T)).