17 Questions
What characteristic of Mycobacteria is responsible for their resistance to staining with commonly used basic aniline dyes?
High lipid content in the cell wall
Which Mycobacterium strain is included in the Mycobacterium tuberculosis Complex?
Mycobacterium bovis
What is the typical route of transmission for Tubercle bacilli causing TB?
Through respiratory droplets (sneezing or talking)
In infected individuals, what can potentially lead to the reactivation of TB?
Granuloma formation
What biological components are typically found in a granuloma formed during TB infection?
Lymphocytes, macrophages, fibroblasts, and capillaries
What is the purpose of a positive PPD skin test in the clinical diagnosis of primary TB?
To assess immune response to TB
What is the term used to describe the seeding of many organs outside the pulmonary tree with AFB through hematogenous spread?
Miliary TB
Which organ infection is referred to as Pott disease?
Skeletal TB of the spine
Which characteristic can be seen in the colonies of Mycobacterium tuberculosis?
Raised, dry, rough, and buff-colored appearance
What is the typical temperature range for the optimal growth of Mycobacterium tuberculosis?
35°C to 37°C
What is the standard treatment duration for pulmonary TB with isoniazid and rifampin?
9-month course
Which type of Mycobacterium is described as a rare cause of mycobacteriosis known as Buruli ulcer?
Mycobacterium ulcerans
What type of colonies does Mycobacterium marinum form when grown in or exposed to light?
Yellow in color
Which form of tuberculosis is caused by Mycobacterium marinum and occurs when traumatized skin comes into contact with salt water or inadequately chlorinated fresh water?
Swimming pool granuloma
What type of colonies do Mycobacterium scrofulaceum form?
Smooth, glistening, and opaque
Which Mycobacterium species is implicated in diseases of fish and isolated from aquariums?
Mycobacterium marinum
What is a common clinical manifestation of Mycobacterium marinum infection in humans?
Swimming pool granuloma
Study Notes
Mycobacteria Characteristics
- Slender, slightly curved or straight, rod-shaped organisms
- Nonmotile and do not form spores
- Cell wall has extremely high lipid content, resisting staining with basic aniline dyes
- Acid-fastness allows them to resist decolorization with acid-ethanol
Mycobacterium Tuberculosis Complex
- Consists of M. tuberculosis, M. bovis, M. africanum, M. canettii, and M. microti
- M. bovis includes the vaccination strain bacillus Calmette-Guérin
Mycobacterium Tuberculosis (TB)
- Usually a disease of the respiratory tract
- Acquired from persons with active disease who are excreting viable bacilli
- Granuloma formation leads to healing, fibrosis, encapsulation, and calcification
- Potential for reactivation of TB in infected individuals
- Clinical diagnosis: positive PPD skin test, confirmed by stained smear and culture of sputum, gastric aspirates, or bronchoscopy specimens
Extrapulmonary Tuberculosis
- Miliary TB: seeding of many organs outside the pulmonary tree with AFB through hematogenous spread
- Can infect almost any organ of the body
- Manifestations: pleurisy, lymphadenitis, genitourinary TB, skeletal TB (Pott disease), meningitis
Mycobacterium Characteristics
- Colonies are typically raised, with a dry, rough appearance
- Nonpigmented and buff-colored
- Elaboration of cord factor results in characteristic cord formation
- Optimal growth at 35° C to 37° C
- Positive for niacin accumulation, reduction of nitrate to nitrite, and production of catalase
- Grows on thiophene-2-carboxylic acid hydrazide (T2H)
Treatment
- Pulmonary TB: 9-month course of therapy with isoniazid and rifampin
Other Mycobacteria
- Mycobacterium scrofulaceum: causes cervical lymphadenitis in children
- Mycobacterium simiae: isolated from the lymph nodes of monkeys
- Mycobacterium ulcerans (Buruli ulcer): acid-fast cells are long, without beading or crossbanding
- Mycobacterium marinum: implicated in diseases of fish, causes cutaneous infections in humans, and is susceptible to rifampin and ethambutol.
Explore the characteristics of mycobacteria, focusing on their slender, rod-shaped morphology and unique cell wall with high lipid content. Learn about the acid-fastness property that allows mycobacterial cells to resist staining with basic aniline dyes commonly used in Gram stain.
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