Nocardia niwae sp. nov., isolated from human pulmonary sources

Abstract

Members of the genus Nocardia are responsible for cutaneous, pulmonary and disseminated human infections. From 2003 to 2008, four nocardioform strains (W8027, W8681, W9071 and W9241T) were isolated from patients in the state of Florida, USA. Ribosomal gene sequencing analysis suggested that a novel species of the genus Nocardia had been isolated. These strains were subjected to a taxonomic analysis using a polyphasic approach. Phenotypic analyses included morphological examination, biochemical profiling and antimicrobial susceptibility testing. Molecular studies included 16S rRNA and DNA gyrase B subunit (gyrB) gene sequence analyses and DNA–DNA hybridization. Phylogenetic neighbours were determined through 16S rRNA and gyrB gene sequence analyses. Phenotypic characteristics that differentiated the novel isolates from phylogenetically related species were growth at 45 °C, and three of the four novel strains utilized l-rhamnose. The antimicrobial profiles could not reliably distinguish the novel species from related nocardiae. Analysis showed that the 16S rRNA gene sequences of the four novel isolates were identical. The blast analysis of the near full-length 16S rRNA gene showed 99.2 % sequence similarity to Nocardia araoensis DSM 44729T, Nocardia arthritidis DSM 44731T and Nocardia beijingensis JCM 10666T, 98.7 % to Nocardia amamiensis DSM 45066T, 98.2 % to Nocardia pneumoniae JCM 12119T and 97.8 % to Nocardia takedensis JCM 13313T. Analysis of partial gyrB gene sequences showed that the novel isolates had 95.4 % similarity to N. arthritidis DSM 44731T, 95.3 % to Nocardia gamkensis DSM 44956T, 94.4 % to N. pneumoniae JCM 12119T, 93.8 % to Nocardia asiatica DSM 44668T, 93.5 % to N. amamiensis DSM 45066T, 93.4 % to N. beijingensis JCM 10666T and 93.2 % to N. araoensis DSM 44729T. The DNA–DNA relatedness values between the four novel strains were 86–89 %; the relatedness value for strain W9241T compared with N. beijingensis JCM 10666T was 47 % and 46 % with N. araoensis DSM 44729T, 44 % with N. arthritidis DSM 44731T, 32 % with N. amamiensis DSM 45066T and 20 % with N. asiatica DSM 44668T. The results of the taxonomic analysis suggested that the new isolates represent a novel species of the genus Nocardia for which the name Nocardia niwae sp. nov. is proposed. The type strain is W9241T (=DSM 45340T=CCUG 57756T).