Contemporary Approaches in the Diagnosis and Study of Mycobacteria

The genus Mycobacterium comprises structurally a complex of highly adaptive bacteria of major clinical importance. While tuberculosis remains a leading cause of mortality from infectious diseases worldwide, nontuberculous mycobacteria (NTM) are gaining increasing clinical relevance, particularly among immunocompromised patients. The unique structure of mycobacterial cell wall and the slow growth of these organisms necessitate the use of specialized microscopic approaches for their investigation and diagnosis. Despite the advances in molecular diagnostics, microscopy remains a rapid and cost-effective key diagnostic tool, however limited by subjectivity and reduced sensitivity at low bacterial loads. The recent integration of artificial intelligence has significantly enhanced light and fluorescence microscopy by enabling an automated and standardized detection of the acid-fast bacilli. The advanced high-resolution techniques, including electron and cryo-electron microscopy, provide detailed insights into mycobacterial ultrastructure and intracellular behaviour, contributing to a deeper understanding of their pathogenicity and drug resistance. This review summarizes the classical and the modern microscopic approaches and highlights their complementary roles in diagnosistic and fundamental studies of mycobacteria.