Question

Which pulmonary infections are associated with cavitary lesions of the lungs? Which mycobacterial species are included in the Mycobacterium tuberculosis Complex? List the 4 most common species. Which organism in the M.tb Complex is often identified by the niacin test? Define the following terms relative to mycobacteria: 3. 4. 5. 6. a. Photochromogen b. Scotochromogen c. Nonphotochromogen d. Rapid grower 7. List 2 AFB media which are egg-based. 8. List 2 AFB media which are chemically defined agar-based media. 9. List 2 liquid media used to isolate AFB. 10. List 4 antibiotics which are recommended for the treatment of M. tuberculosis. 11. The organism isolated from this patient has the following biochemical characteristics: Tween 80 hydrolysis negative Arylsulfatase production negative Urease production negative Tellurite reduction = positive Nonphotochromogen Growth rate >7 days Niacin production negative Nitrate reductase negative Semi-quantitative catalase positive Pyrazinamidase production-positive What is the identity of this AFB? 12. What predisposing factors contributed to this patient's acquiring this mycobacterial infection?

Answer 1

3. Cavitary lung lesion are seen as lucent areas contained within a mass, consolidation or nodule.

The cavitary lesions of lungs can be seen in infections like pneumonia, lung abscess or tuberculosis.

Tuberculosis is an infectious lung disease caused by mycobacterium tuberculi.

4. Mycobacterium species can be classified into two:

a) Mycobacterium tuberculosis complex

b) Non mycobacterium tuberculosis complex

Mycobacterium tuberculosis complex includes bacterias like M. tuberculosis, M. bovis, M. bovis BCG, Mycobacterium africanum.

5. Niacin test is a laboratory test used in tuberculosis infection. It detects the presence of niacin or nicotinic acid in aqueous extracts of the bacterial culture.

Niacin test is used to identify mycobacterium tuberculosis.

6. Photochromogen are the slow grower microorganisms that exhibit pigmentation when exposed to light. Photochromogens do not exhibit or exhibit little  pigmentation in dark conditions but become highly pigmented when exposed to light. For eg: mycobacterium kansasii.

nonchromogens are slow grower microorganisms that do not show any type of pigmentation regargless of the culture and exposure to light. Example : mycobacterium avium

scotochromogens are slow grower microorganisms that produce orange yellow pigmentation and are not affected by exposure to dark or light condition. Example : mycobacterium gordonae.

Rapid growers : rapid growers are one of the class of mycobacterium classified by Runyon based on their rate of growth. These mycobacterium grow and develop colonies within 5 days and are nin pigmented.