High Intraspecific Genetic Diversity ofNocardia brasiliensis, a Pathogen Responsible for Cutaneous Nocardiosis Found in France: Phylogenetic Relationships by Usingsodandhsp65Genes

Abstract

This study aims at genetic characterization and phylogenetic relationships of Nocardia brasiliensis focusing by using housekeeping rrs, hsp65, and sodA genes. N. brasiliensis is the species responsible for 80% of cases of actinomycetoma, one form of cutaneous nocardiosis which occurs mainly in tropical regions reaching immunocompetent patients in which the disease can lead to amputation. We analyze 36 indigenous cases of N. brasiliensis that happened in France. Phylogenetic analysis targeting rrs gene showed no robustness at phylogenetic nodes level. However, the use of a concatenation of hsp65 and sodA genes showed that the tested strains surprisingly ranked in 3 well-defined genotypes. Genotypes 2 and 3 were phylogenetically closer to each other and both diverged from genotype 1 sustained by a high bootstrap of 81%. This last genotype hosts all the cases of pulmonary forms (3), the sole cerebral form, and almost all the cases of immunocompromised patients (3 out of 4). Moreover, excepting one of them, all the strains belonging to this group present a susceptibility to imipenem which is not the case in the other genotypes that rarely count among them strains being susceptible to this drug. The haplotype diversity (Hd) of hsp65 (0.927) and sodA (0.885) genes was higher than that of rrs (0.824). For this gene, we obtained 16 polymorphic sites whereas, for hsp65 and sodA genes, up to 27 and 29 were identified, respectively. This study reveals that these two genes have an important genetic discriminatory power for the evaluation of the intraspecies genetic variability of N. brasiliensis and they may be useful for identification purposes at species level. This study also reveals the possible existence of a new species harbored by genotype 1.

Genetic variability of the 16S rRNA gene of Nocardia brasiliensis, the most common causative agent of actinomycetoma in Latin America and the Caribbean

“…The rest of the sequences form clusters with different restriction patterns showing the discrepancy between strains of the same study species, thus conforming 6 more ribotypes. The results suggest the existence of subgroups within N. brasiliensis with more significant variability than previously reported [14][15][16][17] .…”

“…In the study published by Kosova-Maali et al . 16 in 2018, where they worked with 36 strains of N. brasiliensis obtained from clinical cases, they were able to identify three well-defined genotypes by polymorphisms of the constitutive genes hsp65 and sodA ; this finding related the genotype and clinical presentation of actinomycetoma among the different strains. In addition, the similarity percentages with reference strains were reported to range from 99.39% to 99.57%.…”

“…Although it was first described phenotypically and biochemically in 1959 20 , its current name was only included in the 'Approved Lists of Bacterial Names' in 1980 22,23 . However, its peculiarities and taxonomic problems have not been solved, especially the detection of variations that indicate a poorly studied diversity within the same species [14][15][16][17] .…”

“…From 2012 to the present date, there are only 52 publications on N. brasiliensis. Of these, only four have studied its genetic variability and susceptibility to antibiotics [14][15][16][17] . With so little information, it is still considered a homogeneous species, which could cause inadequate epidemiological reporting and complicate the clinical approach.…”

Lymphocutaneous nocardiosis in an immunocompromised patient

“…Es causada por varios microorganismos saprofíticos del suelo del género Nocardia ( 1) que afecta principalmente a pacientes inmunodeprimidos . Su curso generalmente es crónico y con tendencia a la recaída y la forma de presentación suele ser la afectación pulmonar, cerebral o cutánea (2) .…”