rpoB sequence-based identification of Mycobacterium avium complex species

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• The Mycobacterium avium complex (MAC) consists of slow-growing mycobacteria implicated in opportunistic infections and zoonoses.
• Accurate speciation of MAC isolates is crucial for clinical diagnosis and epidemiological tracking of infection sources.

Purpose of the Study:

• To evaluate the utility of partial rpoB gene sequencing for rapid and accurate species-level identification of MAC isolates.
• To assess the potential of this method for detecting novel MAC species.

Main Methods:

• Sequencing of a 711 bp variable fragment of the rpoB gene using Myco-F/Myco-R primers.
• Analysis of sequence divergence among MAC reference strains and clinical isolates.
• Confirmation of unique isolates using 16S rDNA, ITS, and hsp65 sequencing and phylogenetic analyses.

Main Results:

• A 0.7-5.1% divergence was observed among MAC reference strains, with M. chimaera and M. intracellulare being closely related.
• Using a 0.7% divergence cut-off, 83% of 100 clinical isolates were identified as M. avium, 8% as M. intracellulare, and 2% as M. chimaera.
• Seven isolates showed <99.3% rpoB sequence similarity to reference strains, indicating potential novel species.

Conclusions:

• Partial rpoB gene sequencing provides a one-step method for species-level identification of MAC isolates.
• This technique facilitates the detection of potentially novel MAC species, enhancing diagnostic capabilities.