| Summary: | ThisstudyaimsatgeneticcharacterizationandphylogeneticrelationshipsofNocardiabrasiliensisfocusingbyusinghousekeeping 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 showednorobustnessatphylogeneticnodeslevel.However,theuseofaconcatenationofhsp65andsodAgenesshowedthatthe testedstrainssurprisinglyrankedin3well-definedgenotypes.Genotypes2and3werephylogeneticallyclosertoeachotherand bothdivergedfromgenotype1sustainedbyahighbootstrapof81%.Thislastgenotypehostsallthecasesofpulmonaryforms(3), the sole cerebral form, and almost all the cases of immunocompromised patients (3 out of 4). Moreover, excepting one of them, allthestrainsbelongingtothisgrouppresentasusceptibilitytoimipenemwhichisnotthecaseintheothergenotypesthatrarely 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 and29wereidentified,respectively.Thisstudyrevealsthatthesetwogeneshaveanimportantgeneticdiscriminatorypowerforthe evaluationoftheintraspeciesgeneticvariabilityofN.brasiliensisandtheymaybeusefulforidentificationpurposesatspecieslevel. Thisstudyalsorevealsthepossibleexistenceofanewspeciesharboredbygenotype1
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