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May 14
Acid-fast bacteria are a group of bacteria that are resistant to decolorization by acid-alcohol during the staining process. This characteristic is due to the high lipid content in their cell walls, specifically mycolic acids. The most well-known acid-fast bacteria is Mycobacterium tuberculosis, the causative agent of tuberculosis. Other examples include Mycobacterium leprae, the causative agent of leprosy, and Nocardia species. Acid-fast staining is commonly used to identify these bacteria in clinical samples.
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Google Gemini AI
May 14
Acid-Fast Bacteria
Definition:
Bacteria that retain a pink or red color after being stained with carbolfuchsin (a bright red dye) and then decolorized with an acid/alcohol solution.
Cell Wall Structure:
- Unique cell wall composition called the mycobacterial cell wall
- Contains mycolic acids (long-chain fatty acids) embedded in a peptidoglycan matrix
- Impedes the penetration of acid-alcohol and other solvents, resulting in acid-fastness
Characteristics:
- Gram-positive staining
- Slow growth rate
- Aerobic or anaerobic
- Non-motile
- Rod-shaped or filamentous
- Some species are pathogenic
Examples:
- Mycobacterium tuberculosis: Causes tuberculosis
- Mycobacterium leprae: Causes leprosy
- Mycobacterium avium complex (MAC): Causes lung infections in immunocompromised individuals
- Non-tuberculous mycobacteria (NTM): Cause skin, lymph node, and lung infections
Acid-Fast Staining:
- Ziehl-Neelsen staining: Most commonly used method
- Carbol fuchsin is applied to the specimen, which is then heated to enhance dye penetration
- Acid-alcohol solution is used to remove dye from non-acid-fast bacteria
- Acid-fast bacteria retain the dye and appear pink or red
Clinical Significance:
- Acid-fast staining is used to diagnose diseases caused by acid-fast bacteria, such as tuberculosis and leprosy
- Used to differentiate acid-fast bacteria from other bacterial species in sputum, tissue, or other samples
Antimicrobial Susceptibility:
- Acid-fast bacteria are generally resistant to many antibiotics
- Treatment requires prolonged courses of multiple antibiotics
- Drug resistance is an ongoing concern, especially in Mycobacterium tuberculosis
Definition:
Bacteria that retain a pink or red color after being stained with carbolfuchsin (a bright red dye) and then decolorized with an acid/alcohol solution.
Cell Wall Structure:
- Unique cell wall composition called the mycobacterial cell wall
- Contains mycolic acids (long-chain fatty acids) embedded in a peptidoglycan matrix
- Impedes the penetration of acid-alcohol and other solvents, resulting in acid-fastness
Characteristics:
- Gram-positive staining
- Slow growth rate
- Aerobic or anaerobic
- Non-motile
- Rod-shaped or filamentous
- Some species are pathogenic
Examples:
- Mycobacterium tuberculosis: Causes tuberculosis
- Mycobacterium leprae: Causes leprosy
- Mycobacterium avium complex (MAC): Causes lung infections in immunocompromised individuals
- Non-tuberculous mycobacteria (NTM): Cause skin, lymph node, and lung infections
Acid-Fast Staining:
- Ziehl-Neelsen staining: Most commonly used method
- Carbol fuchsin is applied to the specimen, which is then heated to enhance dye penetration
- Acid-alcohol solution is used to remove dye from non-acid-fast bacteria
- Acid-fast bacteria retain the dye and appear pink or red
Clinical Significance:
- Acid-fast staining is used to diagnose diseases caused by acid-fast bacteria, such as tuberculosis and leprosy
- Used to differentiate acid-fast bacteria from other bacterial species in sputum, tissue, or other samples
Antimicrobial Susceptibility:
- Acid-fast bacteria are generally resistant to many antibiotics
- Treatment requires prolonged courses of multiple antibiotics
- Drug resistance is an ongoing concern, especially in Mycobacterium tuberculosis
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