Mycobacteria Quiz

Mycobacteria Overview

• Mycobacterium is a genus of gram-positive bacilli known for acid-fastness, illustrated by Mycobacterium tuberculosis (MTB), the agent of tuberculosis.
• Additional key species include M. leprae (leprosy), M. kansasii, M. avium-intracellulare, M. scrofulaceum, M. fortuitum, M. marinum, and M. ulcerans.
• Tuberculosis remains a global health threat, infecting a third of the world population and causing nearly 2 million deaths annually.

General Characteristics of Mycobacteria

Bacteriology

• Mycobacteria are slender, poorly staining bacilli, non-motile, and obligate aerobes that do not form spores.
• Their cell wall is rich in mycolic acids and lipoarabinomannan (LAM), contributing to their waxy, hydrophobic nature and high lipid content (over 60%).
• Acid-fastness is a key staining characteristic; stained cells resist decolorization and require extreme conditions to be properly stained.

Growth and Classification

• Mycobacteria are strict aerobes and exhibit slow growth; for example, MTB flourishes in 10% carbon dioxide at a pH of 6.5-6.8.
• Nutritional requirements differ among species, impacting their ability to grow in various environments.
• Over 120 mycobacterial species have been identified, initially classified based on phenotypic characteristics, but increasingly categorized genetically.

Pathogenic Bacteria: Mycobacterial Diseases

• Diseases linked to mycobacteria are often slow-progressing, chronic, and elicit a granulomatous response.
• MTB is primarily human-associated, while other species can infect various hosts or exist freely in the environment.
• The infectivity of pathogenic species is high, yet virulence is moderate in healthy individuals.

Mycobacterium Tuberculosis (MTB) Details

Overview of Disease

• MTB causes tuberculosis, characterized by chronic pneumonia, fever, cough, and weight loss, historically termed "consumption".
• Extra-pulmonary tuberculosis can occur, notably affecting the central nervous system, leading to severe outcomes.
• Most infections are asymptomatic with detectable immune responses like skin test positivity; disease may manifest after extended latency.

Bacteriology of MTB

• MTB is a slim, acid-fast rod, typically resistant to common disinfectants and conditions. It thrives at 37°C, requiring specialized media for growth.
• Colonies grow slowly, appearing after 3-6 weeks in enriched media like Löwenstein-Jensen, which inhibits non-mycobacterial organisms.
• MTB’s unique characteristics include significant niacin production, contributing to its identification.
• Its cell wall is composed of mycolic acids and LAM, with various protein and polysaccharide antigens, including tuberculin.

Treatment and Control

• Effective antimicrobial therapies exist but typically require multiple drugs for extended durations, essential for successful treatment.
• Control measures are challenging in economically disadvantaged regions; thus, tuberculosis remains a leading cause of bacterial mortality worldwide.

Test your knowledge on various types of mycobacteria, including Mycobacterium tuberculosis and Mycobacterium leprae. This quiz will delve into the characteristics, diseases, and classifications of these important bacteria. Enhance your understanding of how they impact human health.