Mycobacterium Tuberculosis Bacteria

• The following notes cover the classification, reservoir, transmission, virulence factors, disease management, and prevention of several bacteria.

Mycobacterium tuberculosis

• Classified as acid-fast bacilli, nonmotile, and an obligate aerobe.
• Cell wall contains mycolic acid, making it hydrophobic and prone to clumping.
• Not detectable by Gram stain due to high lipid content.
• Primary reservoir is human lungs.
• Transmitted through inhalation of respiratory droplet nuclei from coughing, direct contact with discharge, or indirectly through contaminated utensils/fomites.
• Virulence factors include catalase and mycolic acid in the cell wall.
• Causes tuberculosis, a chronic respiratory ailment primarily affecting the lungs.
• Tuberculosis is characterized by tubercle formation in tissues, leading to caseation, necrosis, and calcification.
• Symptoms include afternoon fever, night sweats, malaise, weight loss, cough, and hemoptysis.
• Managed with antibiotic therapy (DOTS by the Department of Health), BCG vaccine, respiratory isolation, and teaching proper coughing and disposal techniques.

Mycobacterium leprae

• Classified as acid-fast bacilli, nonmotile, and a facultative anaerobe.
• Similar to M. tuberculosis, its cell wall contains mycolic acid.
• Reservoirs include human respiratory tracts/skin and armadillos.
• Transmitted through prolonged exposure to nasal secretions of lepromatous patients or inoculation through skin/mucous membrane breaks.
• Virulence factors are catalase and mycolic acid in the cell wall.
• Causes leprosy (Hansen’s disease), leading to nerve damage and impairments like clawed hands/toes, foot drop, and leonine appearance.
• Managed with multiple drug therapy, isolation, counseling, separation of neonates from lepromatous mothers, and health education.
• Acid-fast staining involves carbol fuchsin (primary stain), heating (mordant), acid alcohol (decolorizer), and methylene blue (counterstain).

Borrelia burgdorferi

• Requires special staining due to its helix shape.
• Motile spirochete with an endoflagellum and is an obligate aerobe.
• Reservoir is ticks, specifically the blacklegged tick Ixodes scapularis
• Transmitted through tick bites, especially in endemic areas.
• Outer surface protein C (OspC) enables survival in blood by binding and stopping complement.
• Causes Lyme disease, which is endemic in the Northeast US.
• Stage 1 presents with erythema migrans (a unique skin lesion) and flu-like symptoms.
• Stage 2 occurs weeks to months later, involving arthralgia/arthritis, neurological issues (meningitis, facial nerve palsy, radiculopathy), and cardiac disease.
• Stage 3 begins months to years later, with chronic skin, nervous system, or joint involvement.
• Management includes early diagnosis, antibiotic therapy, protective clothing, and tick control.

Treponema pallidum

• Gram-negative, thin, tightly coiled spirochete with corkscrew-like motion.
• Motile, microaerophilic, and possesses axial filaments and an endoflagellum.
• Human genital tract is the reservoir.
• Transmission occurs through sexual contact, transplacental transfer, or indirectly via fomites.
• Virulence factors include endoflagella and endotoxin.
• Causes syphilis, a chronic infectious STD that starts in mucous membranes and becomes systemic.
• Also causes congenital syphilis, which can lead to miscarriage due to fetal circulation spread.
• Management involves antibiotic therapy and sex education.

Leptospira interrogans

• Gram-negative, thin, coiled spirochete with hooks on both ends (shepherd’s crook appearance).
• Motile, obligate aerobe with an endoflagellum.
• Reservoirs include human kidney tubules, lake waters, sewage, and the sea.
• Transmitted through direct contact with infected urine.
• Organisms penetrate broken skin/mucous membranes (feet) or through swallowing contaminated water.
• Motility (endoflagella) and endotoxin contribute to virulence.
• Causes leptospirosis, a zoonotic infectious bacterial disease affecting renal tubules via food/water contamination or skin inoculation.
• Management includes antibiotic therapy, sanitation, proper disposal of urine wastes, rodent control, and animal vaccination.