Acid-fast bacilli

Acid-fast bacilli (AFB) are a group of bacteria that have certain unique characteristics, including the ability to retain certain stains even after being washed with an acid solution. This property is known as acid-fastness and is a key diagnostic feature used in the identification of these bacteria.

Characteristics

Acid-fast bacilli are characterized by their ability to retain the red color of the carbol fuchsin stain in the Ziehl-Neelsen stain method, even after being washed with an acid-alcohol solution. This is due to the high lipid content in their cell walls, which prevents the stain from being washed out.

Types of Acid-Fast Bacilli

There are several types of acid-fast bacilli, but the most well-known is Mycobacterium tuberculosis, the bacterium that causes tuberculosis. Other types include Mycobacterium leprae, which causes leprosy, and Nocardia species, which can cause a variety of infections.

Diagnosis

Diagnosis of infections caused by acid-fast bacilli is typically done through microscopic examination of a stained sample. The Ziehl-Neelsen stain is the most commonly used method, but other techniques, such as the Kinyoun stain, can also be used. In addition to staining, culture of the bacteria can also be used for diagnosis.

Treatment

Treatment of infections caused by acid-fast bacilli depends on the specific type of bacterium involved. For Mycobacterium tuberculosis, a combination of antibiotics is typically used, including isoniazid, rifampin, pyrazinamide, and ethambutol. Treatment for Mycobacterium leprae typically involves a combination of dapsone, rifampin, and clofazimine.

See Also

• Mycobacterium
• Ziehl-Neelsen stain
• Tuberculosis
• Leprosy

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