Question 1

If a person has had TB during his or her lifetime, how likely is it that the person will get the disease again?

Accepted Answer

People who have had TB in the past have a 5% to 15% chance of developing the disease again, especially if they have risk factors such as a weakened immune system.

Question 2

A patient with Hodgkin disease is feeling bad, so he visits his physician. The physician's clinical examination reveals submandibular lymphadenitis, subcutaneous nodules, painful swellings, ulcers progressing to abscesses, and draining fistulas. What organism is probably producing these symptoms?

Accepted Answer

The symptoms described are consistent with infection caused by Mycobacterium haemophilum, a slow-growing mycobacterium that is known to cause lymphadenitis, skin nodules, abscesses, and fistulas in immunocompromised individuals, particularly those with Hodgkin disease. Mycobacterium tuberculosis is a recognized cause of lymphadenitis, but it is associated with the development of caseating granulomas rather than abscesses and fistulas. Mycobacterium avium and M. gordonae are nontuberculous mycobacteria that can cause lymphadenitis and skin infections, but they are not typically associated with the development of abscesses and fistulas.

Question 3

This disease is slowly progressive, malignant, and, if untreated, life threatening. It is characterized by skin lesions and progressive, symmetric nerve damage. Lesions of the mucous membranes of the nose may lead to destruction of the cartilaginous septum, resulting in nasal and facial deformities. What disease is this?

Accepted Answer

The disease described is Hansen disease, also known as leprosy. It is caused by the bacterium Mycobacterium leprae and primarily affects the skin and nerves. If left untreated, it can lead to severe disfigurement and disability. Extrapulmonary TB and non-Mycobacterium tuberculosis pulmonary disease are not characterized by skin lesions and do not typically affect the nose or facial structure. M. xenopi is a type of Mycobacterium, but it is not known to cause Hansen disease.

Question 4

What classifies an organism as a multidrug-resistant Mycobacterium tuberculosis?

Accepted Answer

Multidrug-resistant Mycobacterium tuberculosis (MDR-TB) is defined by resistance to at least the two most powerful anti-TB drugs, isoniazid and rifampin.

Question 5

What component of mycobacteria is used for identification in nucleic acid hybridization assays?

Accepted Answer

Ribosomal RNA (rRNA) is commonly used in nucleic acid hybridization assays for identification of mycobacteria. This is because rRNA is highly conserved and contains both variable and conserved regions that can be targeted for identification. Additionally, rRNA is present in high quantities in bacterial cells, making it a reliable target for detection. DNA, transfer RNA, and messenger RNA are also present in mycobacteria, but rRNA is the most commonly used target for identification.

Question 6

How has the treatment of mycobacterial disease changed in light of the multidrug-resistant strains of mycobacteria that are being isolated?

Accepted Answer

The treatment of mycobacterial disease has changed in response to multidrug-resistant strains of mycobacteria by using combination therapy with three or four drugs instead of a single drug. This approach has been found to be more effective in treating multidrug-resistant strains and preventing the development of further drug resistance.

Question 7

A 35-year-old man travels on a multidestination vacation over a 2 month period, including lengthy stops in tropical Africa and Southeast Asia. Six weeks after returning come home to the United States, he develops a productive cough, fatigue, weight loss, low-grade fever, and night sweats. What disease should the physician consider as a result of his travel history?

Accepted Answer

The symptoms described are consistent with pulmonary TB, which is endemic in both tropical Africa and Southeast Asia. The prolonged incubation period makes it possible for symptoms to develop after the patient has returned home. Streptococcal and gram-negative pneumonia typically do not have such a delayed onset, and primary atypical pneumonia is less likely given the patient's travel history.

Question 8

What is the antigen used in the purified protein derivative (PPD) skin test?

Accepted Answer

The antigen used in the PPD skin test is a purified protein extracted from the cell wall of Mycobacterium tuberculosis. This protein is called tuberculin and it triggers an immune response in individuals who have been previously exposed to or infected with the bacteria. This immune response causes a raised bump or redness at the site of the skin test, indicating a positive result.

Question 9

A sputum culture from a patient in Texas has buff colored colonies growing in approximately 4 weeks. After exposure to light, the colonies turn intense yellow. This isolate is most likely

Accepted Answer

The buff colored colonies growing in 4 weeks followed by intense yellow color upon light exposure is a classic feature of M. kansasii. This organism is commonly found in Texas and is known to cause pulmonary disease in immunocompromised patients or those with pre-existing lung disease. M. scrofulaceum and M. xenopi are also slow growing organisms that can cause pulmonary disease, but do not typically exhibit the yellow color change. M. fortuitum is a rapid-grower and would not take 4 weeks to show growth.

Question 10

The Centers for Disease Control and Prevention (CDC) recommends all the following drugs for the treatment of Mycobacterium tuberculosis, except

Accepted Answer

The CDC does not recommend ciprofloxacin for the treatment of Mycobacterium tuberculosis. The recommended drugs for tuberculosis treatment are isoniazid, rifampin, ethambutol, and pyrazinamide.

Question 11

All of the following are biochemical tests for the identification of Mycobacterium spp., except

Accepted Answer

PYR is not a biochemical test used for the identification of Mycobacterium spp. The other three choices (niacin, nitrate, and catalase) are commonly used tests for Mycobacterium identification.

Question 12

A child presents to his physician with fever, a nonproductive cough, and shortness of breath. The physician orders a routine sputum culture and an acid-fast bacillus culture and smear. The smear shows red organisms arranged in ropes. What is the most probable cause of this child's fever and cough?

Accepted Answer

The presence of red organisms arranged in ropes on an acid-fast bacillus smear is characteristic of Mycobacterium tuberculosis, which causes pulmonary tuberculosis. The symptoms of fever, nonproductive cough, and shortness of breath are also consistent with tuberculosis. Mycobacterium leprae causes leprosy, which typically does not involve the respiratory system. M. avium and M. intracellulare can cause pulmonary infections in immunocompromised individuals but do not typically result in the symptoms described in this case.

Question 13

The most common nontuberculosis mycobacterium (NTM) infecting humans

Accepted Answer

The most common NTM infection in humans is caused by the M. avium-intracellulare complex, which can lead to lung infections in people with weakened immune systems or chronic lung diseases. While M. marinum, M. ulcerans, and M. haemophilium are also NTMs that can infect humans, they are less common than M. avium-intracellulare complex.

Question 14

All of the following are biochemical tests for the identification of Mycobacterium spp., except

Accepted Answer

Gelatin liquefaction is not a biochemical test for the identification of Mycobacterium spp. The other options (B, C, D) are commonly used tests for the identification of Mycobacterium spp.

Quiz 26: Mycobacterium Tuberculosis and Nontuberculous Mycobacteria

If a person has had TB during his or her lifetime, how likely is it that the person will get the disease again?

A patient with Hodgkin disease is feeling bad, so he visits his physician. The physician's clinical examination reveals submandibular lymphadenitis, subcutaneous nodules, painful swellings, ulcers progressing to abscesses, and draining fistulas. What organism is probably producing these symptoms?

What classifies an organism as a multidrug-resistant Mycobacterium tuberculosis?

What component of mycobacteria is used for identification in nucleic acid hybridization assays?

How has the treatment of mycobacterial disease changed in light of the multidrug-resistant strains of mycobacteria that are being isolated?

What is the antigen used in the purified protein derivative (PPD) skin test?

A sputum culture from a patient in Texas has buff colored colonies growing in approximately 4 weeks. After exposure to light, the colonies turn intense yellow. This isolate is most likely

The Centers for Disease Control and Prevention (CDC) recommends all the following drugs for the treatment of Mycobacterium tuberculosis, except

All of the following are biochemical tests for the identification of Mycobacterium spp., except

A child presents to his physician with fever, a nonproductive cough, and shortness of breath. The physician orders a routine sputum culture and an acid-fast bacillus culture and smear. The smear shows red organisms arranged in ropes. What is the most probable cause of this child's fever and cough?

The most common nontuberculosis mycobacterium (NTM) infecting humans

All of the following are biochemical tests for the identification of Mycobacterium spp., except