Conventional and Modern Approaches for Clinical and Laboratory Diagnosis of Tuberculosis

Abstract

AbstractThe Mycobacterium tuberculosis complex (MTBC) is comprised of species M. tuberculosis, M. bovis including M. bovis BCG (vaccine strain), M. caprae, M. pinnipedii, M. africanum, M. microti, M. canettii, “M. mungi”, and “M. orygis” (Woods et al., Susceptibility testing of mycobacteria, nocardiae and other aerobic actinomycetes: approved standard, Wayne, 2011). Mycobacteria are acid-fast bacilli and unlike most other bacteria, they have lipid-rich cell walls and due to the presence of mycolic acid, their cell walls are impermeable to a variety of disinfecting and antimicrobial agents. This makes them resistant to a variety of chemical and pharmaceutical agents. MTBC can survive harsh climates, varying temperatures and can live in deceased hosts for long periods of time (e.g. mummies). Chronic granulomatous disease caused by M. tuberculosis has manifestations, involving primarily lungs but sometimes other organ systems as well. MTBC are 1–10 μm in length, aerobic, non-motile, and slowly growing bacteria with 18–20-h doubling time. MTBC smear morphology shows rods that are known for their serpentine cording due to cord factor trehalose 6, 6 dimycolate. Clinical diagnosis can be done by chest X-ray, mantoux test or symptom check in conjunction with risk factors. Laboratory testing includes smear microscopy, interferon-gamma release assays, culture, rapid-detection, identification, antimicrobial susceptibility testing, and genotyping. Whole-genome sequencing is currently becoming a new norm for direct direction, identification, antimicrobial susceptibility prediction or confirmation and outbreak/contact tracing/contamination investigations. Whole-genome sequencing results in large amounts of data and the bioinformatic tools for analyzing this data remain complex.Keywords Mycobacterium tuberculosis IsoniazidRifampinAntimicrobial susceptibility testingGenotypingWhole genome sequencing