Survey of 150 strains belonging to the Mycobacterium terrae complex and description of Mycobacterium engbaekii sp. nov., Mycobacterium heraklionense sp. nov. and Mycobacterium longobardum sp. nov.

Abstract

A thorough phenotypic and genotypic analysis of 150 strains belonging to the Mycobacterium terrae complex resulted in the identification of a number of previously unreported sequevars (sqvs) within the species known to belong to the complex. For the species Mycobacterium arupense , three sqvs were detected in the 16S rRNA gene, six sqvs in the hsp65 gene and 15 sqvs in the rpoB gene; in Mycobacterium senuense two sqvs were present in each of the three genetic regions; in Mycobacterium kumamotonense four, two and nine sqvs were found, respectively, and in M. terrae three, four and six sqvs were found, respectively. The inappropriate inclusion of Mycobacterium triviale within the M. terrae complex was confirmed. The limited utility of biochemical tests and of mycolic acid analyses for the differentiation of the members of M. terrae complex was also confirmed. The survey allowed the recognition of three previously undescribed species that were characterized by unique sequences in the 16S rRNA, hsp65 and rpoB genes. Mycobacterium engbaekii sp. nov. (proposed previously 40 years ago but never validly published) was characterized by pink photochromogenic pigmentation and rapid growth; phylogenetically it was related to Mycobacterium hiberniae . The type strain of this species, of which eight strains were investigated, is ATCC 27353T ( = DSM 45694T). A cluster of 24 strains was the basis for the description of Mycobacterium heraklionense sp. nov., which has an intermediate growth rate and is unpigmented; nitrate reductase activity is typically strong. Closely related to M. arupense with respect to the 16S rRNA gene, M. heraklionense sp. nov. could be clearly differentiated from the latter species in the other genetic regions investigated. The type strain is NCTC 13432T ( = LMG 24735T = CECT 7509T). Mycobacterium longobardum sp. nov., represented in the study by seven strains, was characterized by a unique phylogenetic location within the M. terrae complex, clearly divergent from any other species. The type strain is DSM 45394T ( = CCUG 58460T).

Mycobacterium arupense, Mycobacterium heraklionense, and a Newly Proposed Species, “Mycobacterium virginiense” sp. nov., but Not Mycobacterium nonchromogenicum, as Species of the Mycobacterium terrae Complex Causing Tenosynovitis and Osteomyelitis

“…An excellent history and species update of the M. terrae complex based on multigene sequencing targets was published by Tortoli et al (1). He noted that the presence of a two nucleotide insertion in helix 18 of the 16S rRNA gene (bp ϳ430 to 500; hypervariable region B or region V3) provided a consistent signature sequence for members of the MTC compared to other slowly growing mycobacteria (37,38).…”

“…An additional eight new species have been validly published since 2006: Mycobacterium arupense (28), Mycobacterium kumamotonense (36), Mycobacterium heraklionense (1), Mycobacterium senuense (40), Mycobacterium minnesotense (41), My-cobacterium longobardum (1), Mycobacterium algericum (42), and Mycobacterium engbaekii (1). Two other MTC species have been described that currently have no standing in nomenclature: "Mycobacterium paraterrae" (43) and "Mycobacterium sinense" (44).…”

“…He noted that the presence of a two nucleotide insertion in helix 18 of the 16S rRNA gene (bp ϳ430 to 500; hypervariable region B or region V3) provided a consistent signature sequence for members of the MTC compared to other slowly growing mycobacteria (37,38). He also characterized several new species in the complex, including Mycobacterium heraklionense and Mycobacterium engbaekii (1).…”

“…Whether one or more members of the complex are true respiratory pathogens has not been established (1,22).…”

“…The initial MTC consisted of two nonchromogenic slowly growing species: M. terrae and Mycobacterium nonchromogenicum (1,2). Phenotypic separation within the group was often difficult, and molecular methods were not available, making establishment of species pathogenicity uncertain (3).…”