Untitled Quiz

Mycobacterium Morphology

• Mycobacterium is a genus of bacteria that is characterized by its slender, slightly curved, or straight rod-shaped morphology.

Mycobacterium Growth Requirements

• Mycobacterium species are obligate aerobes, meaning they require oxygen to grow.
• The growth of most Mycobacterium species takes 2-6 weeks on complex media.
• Mycobacterium leprae, however, does not grow in vitro.
• Some Mycobacterium species, considered rapid growers, can grow in 2-3 days on simple media at a temperature between 20-40°C.

Mycobacterium Tuberculosis Complex

• The Mycobacterium Tuberculosis Complex (MTBC) consists of several species, including: M. tuberculosis, M. bovis, M. microti, M. africanum, M. canettii, M. pinnipedii, M. mungi, and M. orygis.
• M. africanum is associated with tuberculosis in tropical Africa.
• M. microti is linked with tuberculosis in both immunocompetent and immunocompromised individuals.
• M. bovis is primarily found in cattle but can infect other animals and humans.
• M. canettii causes infections in children and HIV-positive patients in Africa.

Mycobacterium Tuberculosis and Robert Koch

• Robert Koch discovered M. tuberculosis.
• Tuberculosis is one of the oldest communicable diseases.

Tuberculosis Infection

• Tuberculosis primarily infects the respiratory tract.
• Transmission occurs through inhalation of airborne droplets containing tubercle bacilli.
• M. tuberculosis evades phagocytosis due to its thick lipid cell wall, which resists the acidic environment and enzymatic conditions that kill most bacteria.

Immune Response to Tuberculosis

• In individuals with adequate cellular immunity, macrophages secrete IL-12 and TNF to enhance the inflammatory response.
• IFN-gamma, also secreted by macrophages, helps destroy intracellular bacteria.
• Mycobacterium infection triggers type IV hypersensitivity.

Tuberculosis Diagnosis

• A positive PPD skin test indicates past infection with M. tuberculosis, not a recent infection.
• Tuberculosis can reactivate into active TB.
• Stained smears and sputum cultures are diagnostic tests for chronic tuberculosis.
• Miliary tuberculosis occurs when tuberculosis spreads to other organs.
• The order of organ involvement in miliary tuberculosis is spleen, liver, bone marrow, kidney, and adrenal gland.
• Miliary tuberculosis spreads hematogenously.
• Children and individuals with HIV are more prone to miliary tuberculosis.
• Genitourinary tuberculosis, which affects kidneys and genital organs, can manifest as typical urinary tract infections and sterile pyuria (renal TB).

Skeletal Tuberculosis

• Skeletal tuberculosis is also known as Pott's Disease.

Meningitis Due to Tuberculosis

• Tuberculosis can infect the meninges through the rupture of a tubercle into the subarachnoid space.

Tuberculosis Treatment

• The primary drugs for pulmonary tuberculosis are rifampin, isoniazid, pyrazinamide, and ethambutol.

BCG Vaccine

• Bacille Calmette-Guerin (BCG) is a live attenuated vaccine derived from M. bovis.

Sample Collection for Mycobacteria

• Mycobacteria can be detected in urine, feces, blood, cerebrospinal fluid (CSF), tissue biopsies, and aspirates from various tissues.
• Delaying specimen processing for Mycobacteria can lead to false-negative results and bacterial contamination.
• Early-morning specimens are recommended for sputum and other respiratory secretions.
• Three consecutive days of specimen collection is recommended for detecting Mycobacteria.
• Two positive sputum smears out of three are sufficient to confirm diagnosis. If only one smear is positive, additional specimens are needed.
• Gastric aspirates and washings are recommended for children and patients unable to produce sputum.
• Pooled specimens should not be processed for Mycobacteria after 12-24 hours as they are contaminated and may contain few viable tubercle bacilli.
• Stool specimens should be frozen if not processed within a few hours of collection.
• 2 mL of CSF is recommended for culture.

Culture Media for Mycobacteria

• Petragani medium is used for heavily contaminated specimens for M. tuberculosis testing.
• Lowenstein-Jensen (L-J) medium is the most widely used solid medium for routine culture.
• Mycobacteria species grow rapidly on liquid media.

Fluorescence Microscopy

• Auramine phenol and auramine rhodamine dyes are used for fluorescence microscopy of smears.