Mycobacteria

Worldwide, tuberculosis remains one of the most common causes of fatal infections, exacerbated by the human immunodeficiency virus pandemic and emergence of drug-resistant Mycobacterium tuberculosis (MTB) strains. Better commercial supplies of various reagents, culturing systems, and molecular detection and identification methods have substantially improved the quality and timeliness of mycobacterial detection and identification. This chapter summarizes the current practice and methods and when applicable, clinical evaluation studies are discussed. Identification of clinical isolates of mycobacteria traditionally includes acid-fast stains, growth rates, macroscopic examination of colony morphologies, utilization of substrates, and metabolic byproducts. Regular blood cultures may recover mycobacteria in the blood circulation. Susceptibility tests for various mycobacteria are assuming more importance in view of the emergence and spread of drug-resistant M. tuberculosis strains and varying susceptibility of other slowly growing and rapidly growing mycobacteria. Nearly all cases of tuberculosis represent reactivation of latent primary M. tuberculosis infection.