Evolution of Laboratory Diagnosis of Tuberculosis

Abstract

Tuberculosis (TB) is an infectious disease of global public health importance caused by the Mycobacterium tuberculosis complex. Despite advances in diagnosis and treatment, this disease has worsened with the emergence of multidrug-resistant strains of tuberculosis. We aim to present and review the history, progress, and future directions in the diagnosis of tuberculosis by evaluating the current methods of laboratory diagnosis of tuberculosis, with a special emphasis on microscopic examination and cultivation on solid and liquid media, as well as an approach to molecular assays. The microscopic method, although widely used, has its limitations, and the use and evaluation of other techniques are essential for a complete and accurate diagnosis. Bacterial cultures, both in solid and liquid media, are essential methods in the diagnosis of TB. Culture on a solid medium provides specificity and accuracy, while culture on a liquid medium brings rapidity and increased sensitivity. Molecular tests such as LPA and Xpert MTB/RIF have been found to offer significant benefits in the rapid and accurate diagnosis of TB, including drug-resistant forms. These tests allow the identification of resistance mutations and provide essential information for choosing the right treatment. We conclude that combined diagnostic methods, using several techniques and approaches, provide the best result in the laboratory diagnosis of TB. Improving the quality and accessibility of tests, as well as the implementation of advanced technologies, is essential to help improve the sensitivity, efficiency, and accuracy of TB diagnosis.

Keywords: diagnosis; laboratory; tuberculosis.

Figure 1

Flow diagram of the laboratory diagnosis process of tuberculosis. When, The ReaSLR method is the rapid liquefaction of sputum samples with a specific reagent called (ReaSLR), USP is universal sample processing, MGIT is mycobacteria growth indicator tube, NAAT is nucleic acid amplification test, The GeneXpert MTB RT-PCR technique is a real-time Polymerization Chain Reaction to detect the presence of M. tuberculosis DNA, MTB/NTM MDR-TB is method PCR multiplex Seegene Anyplex.

Figure 2

Ziehl-Neelsen staining is a specific staining technique used in microbiology laboratories to identify acid-alcohol-fast bacteria. M. tuberculosis in sputum. Ziehl–Neelsen staining at 1000× magnification; M. tuberculosis bacteria appear as thin and red bacilli. (a) The distinctive coloration of M. tuberculosis bacils is represented in red, whether they are arranged in isolation or in groups. Leukocytes and fibrin appear in a shade of blue. This smear was obtained from the patient’s sputum. (b) Another smear is represented, this time from a pathological product, namely bronchial lavage. Bacillus is highlighted in red, and cellular detritus is represented in blue.

Figure 3

Auramine–rhodamine fluorescent stain.

Figure 4

Lowenstein–Jensen medium (LJ) characteristic colonies of M. tuberculosis.

Figure 5

Conventional and widely used NAATs.