Impact of Genotypic Studies on Mycobacterial Taxonomy: the New Mycobacteria of the 1990s

Abstract

The advancement of genetic techniques has greatly boosted taxonomic studies in recent years. Within the genus Mycobacterium, 42 new species have been detected since 1990, most of which were grown from clinical samples. Along with species for which relatively large numbers of strains have been reported, some of the new species of mycobacteria have been detected rarely or even only once. From the phenotypic point of view, among the new taxa, chromogens exceed nonchromogens while the numbers of slowly and rapidly growing species are equivalent. Whereas conventional identification tests were usually inconclusive, an important role was played by lipid analyses and in particular by high-performance liquid chromatography. Genotypic investigations based on sequencing of 16S rRNA gene have certainly made the most important contribution. The investigation of genetic relatedness led to the redistribution of the species previously included in the classically known categories of slow and rapid growers into new groupings. Within slow growers, the intermediate branch related to Mycobacterium simiae and the cluster of organisms related to Mycobacterium terrae have been differentiated; among rapid growers, the group of thermotolerant mycobacteria has emerged. The majority of species are resistant to isoniazid and, to a lesser extent, to rifampin. Many of the new species of mycobacteria are potentially pathogenic, and there are numerous reports of their involvement in diseases. Apart from disseminated and localized diseases in immunocompromised patients, the most frequent infections in immunocompetent people involve the lungs, skin, and, in children, cervical lymph nodes. The awareness of such new mycobacteria, far from being a merely speculative exercise, is therefore important for clinicians and microbiologists

Comparação genotípica de isolados de Corynebacterium pseudotuberculosis de caprinos e ovinos do sertão de Pernambuco

“…Este último foi pautado na detecção de regiões altamente conservadas do genoma, de áreas que sofreram alguma variação como inserção, deleção ou mutação de nucleotí-deos específicos para uma espécie ou mesmo amostra (Tortoli 2003).…”

Mycobacterium pseudoshottsii sp. nov., a slowly growing chromogenic species isolated from Chesapeake Bay striped bass (Morone saxatilis)

“…The greater discriminatory power of molecular methods compared with traditional phenotypic techniques has resulted in a dramatic increase in the identification of previously unrecognized species (Tortoli, 2003). These new taxa comprise isolates of both clinical and environmental origin.…”

Rapid tests for the detection of the Mycobacterium abscessus subsp. bolletii strain responsible for an epidemic of surgical-site infections in Brazil

“…An A/C SNP at nucleotide position 8,148 corresponds to the first base of the 634th gyrB codon (Arg) and is also a synonymous mutation. The T/C SNP at nucleotide position 1,463,374 detected in the 16S rDNA gene does not occur within hypervariable region A or B, which are important for the discrimination of mycobacterial species (Tortoli 2003).…”

“…This was a sudden increase relative to previous years with only 13 cases reported between 2000-2003(ANVISA 2009. Most of the infections were related to laparoscopic or arthroscopic surgeries and were caused by RGM with a Mycobacterium abscessus type 2 polymerase chain reaction (PCR) restriction-enzyme analysis (PRA)-hsp65 pattern (BstE II: 235 and 210 bp; Hae III: 200, 70, 60 and 50 bp) (Devallois et al 1997).…”