Chapter 26: Mycobacterium tuberculosis and Nontuberculous Mycobacteria. All Answers

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MULTIPLE CHOICE 1. What is the optimum culture incubation time for most mycobacteria associated with human disease? a. 2 to 6 weeks b. 1 to 2 weeks c. 5 to 7 days d. 3 to 5 days A Most ... mycobacteria associated with disease require 2 to 6 weeks of incubation on complex media at specific optimum temperatures. REF: 564 OBJ: Level 1: Recall 2. What Mycobacterium spp. fails to grow in vitro? a. Mycobacterium tuberculosis b. M. leprae c. M. avium d. M. marinum B One mycobacterium that is pathogenic for humans, M. leprae, fails to grow in vitro. REF: 564 OBJ: Level 1: Recall 3. All of the following are traditional characteristics used to identify mycobacteria except: a. rate of growth. b. colony morphology. c. gram stain results. d. pigmentation. C Rate of growth, colony morphology, pigmentation, nutritional requirements, optimum incubation temperature, and biochemical test results are traditional characteristics used to differentiate species within the genus Mycobacterium. REF: 573 OBJ: Level 1: Recall 4. How are mycobacterial infections transmitted? a. By blood b. By fomites c. By sexual contact d. By air D The serious nature of tuberculosis disease and the usual airborne route of infection require that special safety precautions be used by anyone handling mycobacterial specimens. REF: 573 OBJ: Level 1: Recall 5. When designing a mycobacterial laboratory, the designers should build in all the following engineering controls to keep the workers safe except: a. inside air vents to outside. b. nonrecirculating ventilation system. c. negative air pressure. d. separate room from main laboratory. A Laboratory design and ventilation play an important role in mycobacteriology laboratory safety. Ideally, the mycobacteriology laboratory should be separate from the remainder of the laboratory and should have a nonrecirculating ventilation system. The area in which specimens and cultures are processed should have negative air pressure in relation to other areas; that is, the airflow should be from clean areas, such as corridors, into less clean areas. REF: 573 OBJ: Level 1: Recall 6. What is the single most important piece of equipment in a mycobacterial laboratory? a. Ultraviolet lights b. Covered centrifuge c. Biological safety cabinet d. CO2 incubator C Because the route of infection by mycobacteria is primarily through inhalation, it is essential that the dispersal of organisms into the air be minimized and that inhalation of airborne bacilli be avoided. The biological safety cabinet is the single most important piece of equipment in a mycobacteriology laboratory. REF: 573 OBJ: Level 1: Recall 7. What is the recommended contact time for most disinfectants in a mycobacteriology laboratory? a. 5 minutes b. 10 to 30 minutes c. 10 minutes d. 60 minutes B The following disinfectants are used in the mycobacterial laboratories to disinfect working surfaces: Phenol soap, 10 to 30 minutes; sodium hypochlorite, 10 to 30 minutes; formaldehyde, 30 minutes; and phenol, 10 to 30 minutes. REF: 573 OBJ: Level 1: Recall 8. What is the purpose of the digestion-decontamination processing of specimens submitted for mycobacterial culture? a. To release all bacteria in the sample b. To make the specimen easier to plate c. To allow chemical decontaminants to kill nonmycobacterial organisms d. To liquefy the outer cell wall of the mycobacteria so that they will grow faster C The purposes of the digestion-decontamination process are to liquefy the sample through digestion of the proteinaceous material and to allow the chemical decontaminating agent to contact and kill the nonmycobacterial organisms. REF: 576 OBJ: Level 1: Recall 9. Decontaminating agents used in the decontamination-digestion process include all of the following except: a. sodium hydroxide. b. N-acetyl-1-cysteine. c. benzalkonium chloride. d. hydrochloric acid. D Sodium hydroxide, N-acetyl-1-cysteine, benzalkonium chloride, and oxalic acid are used as decontaminating chemicals in the digestion-decontamination process. REF: 577 OBJ: Level 1: Recall 10. All of these stains are commonly used to visualize mycobacteria on a smear except: a. Ziehl-Neelsen. b. Kinyoun. c. auramine. d. acridine orange. D The conventional acid-fast staining methods, Ziehl-Neelsen and Kinyoun stains, use carbolfuchsin as the primary stain, acid-alcohol as a decolorizing agent, and a methylene blue counterstain. The Ziehl-Neelsen staining procedure involves the application of heat with the carbolfuchsin stain, whereas the Kinyoun acid-fast stain is a cold stain. The auramine or auramine-rhodamine fluorochrome stains are more sensitive than the carbolfuchsin stains. REF: 577 OBJ: Level 1: Recall 11. What media are recommended for routine culturing of specimens for the recovery of acid-fast bacilli? a. Löwenstein-Jensen and liquid-based media b. Middlebrook 7H10 and cooked meat broth c. Sabouraud dextrose and LIM broth d. Thiosulfate-citrate-bile salts-sucrose (TCBS) and thioglycollate broth A Because some isolates do not grow on a particular agar and each type of culture medium offers certain advantages, a combination of culture media is generally recommended for primary isolation. The use of a solid-based medium, such as Löwenstein-Jensen (LJ) medium, in combination with a liquid-based medium is recommended for routine culturing of specimens for the recovery of AFB. REF: 578 OBJ: Level 1: Recall 12. What constituent of Löwenstein-Jensen (LJ) medium is added to suppress the growth of gram-positives? a. Carbolfuchsin b. Malachite green c. Gentian purple d. Mercurochrome B The basic ingredients in an inspissated egg medium, such as LJ, Petragnani, and American Thoracic Society (ATS) media, are fresh whole eggs, potato flour, and glycerol, with slight variations in defined salts, milk, and potato flour. Each contains malachite green to suppress the growth of gram-positive bacteria. REF: 578 OBJ: Level 1: Recall 13. Middlebrook 7H10 and 7H11 media are enriched with all of the following except: a. oleic acid. b. bovine albumin. c. heme. d. beef catalase. C Serum albumin agar media, such as Middlebrook 7H10 and 7H11 agars, are prepared from a basal medium of defined salts, vitamins, cofactors, glycerol, malachite green, and agar combined with an enrichment consisting of oleic acid, bovine albumin, glucose, and beef catalase. REF: 578 OBJ: Level 1: Recall 14. What is the most sensitive and rapid primary isolation liquid media for Mycobacterium spp.? a. Thioglycollate b. Cooked meat c. 5% NaCl broth d. Middlebrook 7H12 D The most sensitive and rapid primary isolation liquid media are Middlebrook 7H12 and 7H13 (BACTEC 12 B and 13 B). REF: 579 OBJ: Level 1: Recall 15. How long does it take to detect Mycobacterium spp. with the BACTEC method? a. Less than 2 weeks b. 3 weeks c. 4 weeks d. 6 weeks A With the BACTEC method, mycobacteria may be detected in clinical specimens in less than 2 weeks. In general, the time required for isolation and identification of Mycobacterium tuberculosis is reduced from 6 weeks to 3 weeks. REF: 579 OBJ: Level 1: Recall 16. What type of media is recommended for the recovery of Mycobacterium haemophilum? a. Sheep blood agar (SBA) b. Chocolate c. Polysaccharide egg antigen (PEA) d. Löwenstein-Jensen (LJ) B A chocolate agar plate should be included in the primary isolation media for skin and other body surface specimens for the recovery of M. haemophilum, which requires ferric ammonium citrate or hemin for growth. Alternatively, hemin (X) strips or disks used for the identification of Haemophilus spp. can be placed on Middlebrook agar plates. REF: 580 OBJ: Level 1: Recall 17. A microbiologist is checking the mycobacteria cultures. She notices growth in one tube of Löwenstein-Jensen (LJ) that is a buff color, rough, and seems arranged in a cord. It has taken these organisms 4 weeks to grow. What is the most probable organism? a. Mycobacterium leprae b. M. avium c. M. tuberculosis d. M. marinum C Colonies of M. tuberculosis that are rough also exhibit a prominent patterned texture referred to as cording; this texture is the result of tight cohesion of the bacilli. M. tuberculosis has a generation time of 20 to 22 hours and generally grows in culture in approximately 26 days. REF: 581 OBJ: Level 3: Synthesis 18. What are photochromogens? a. Species that produce carotene pigment upon exposure to light b. Species that produce pigment in the light or the dark c. Species whose colonies remain buff colored after exposure to light d. Species whose colonies fluoresce under ultraviolet light A Species that produce carotene pigment upon exposure to light are photochromogens. Color may range from pale yellow to orange. REF: 581 OBJ: Level 1: Recall 19. What are scotochromogens? a. Species that produce carotene pigment upon exposure to light b. Species that produce pigment in the light or the dark c. Species whose colonies remain buff colored after exposure to light d. Species whose colonies fluoresce under ultraviolet light B Species that produce pigment in the light or the dark are scotochromogens. Growth temperature may influence the photoreactive characteristics of a species. REF: 581 OBJ: Level 1: Recall 20. What are nonchromogens? a. Species that produce carotene pigment upon exposure to light b. Species that produce pigment in the light or the dark c. Species whose colonies remain buff colored after exposure to light d. Species whose colonies fluoresce under ultraviolet light C Some Mycobacterium spp., such as M. tuberculosis, are nonchromogenic or nonphotochromogenic. These colonies are a buff color and are nonphotoreactive; exposure to light does not induce pigment formation. REF: 581 OBJ: Level 1: Recall 21. All of the following are biochemical tests for the identification of Mycobacterium spp. except: a. niacin. b. nitrate. c. catalase. d. PYR. D The biochemical tests are based on the enzymes the organisms possess, the substances that their metabolisms produce, and the inhibition of growth on exposure to selected biochemicals: niacin, nitrate reduction, catalase, hydrolysis of Tween 80, iron uptake, arylsulfatase, pyrazinamidase, tellurite reduction, urease, NAP inhibition test, TCH inhibition tests, sodium chloride tolerance, and growth on MacConkey agar. REF: 581 OBJ: Level 1: Recall 22. All of the following are biochemical tests for the identification of Mycobacterium spp. except: a. gelatin liquefaction. b. hydrolysis of Tween 80. c. iron uptake. d. arylsulfatase. A The biochemical tests are based on the enzymes the organisms possess, the substances that their metabolisms produce, and the inhibition of growth on exposure to selected biochemicals: niacin, nitrate reduction, catalase, hydrolysis of Tween 80, iron uptake, arylsulfatase, pyrazinamidase, tellurite reduction, urease, NAP inhibition test, TCH inhibition test, sodium chloride tolerance, and growth on MacConkey agar. REF: 583 OBJ: Level 1: Recall 23. What component of mycobacteria is used for identification in nucleic acid hybridization assays? a. DNA b. Ribosomal RNA c. Transfer RNA d. Messenger RNA B These tests are nonisotopically labeled probes specific to the mycobacterial ribosomal RNA. The ribosomal RNA is released from the cell after sonification. REF: 585 OBJ: Level 1: Recall 24. How has the treatment of mycobacterial disease changed in light of the multidrug-resistant strains of mycobacteria that are being isolated? a. Antibiotic therapy is started sooner in the course of the disease. b. More powerful antibiotics are used to treat mycobacterial disease. c. Combinations of three or four drugs are used instead of a single drug. d. Patients are hospitalized for the duration of their disease. C Random drug resistance has a good chance of developing when only one antimycobacterial agent is used or if the patient is on multidrug therapy and fails to complete the course of medication. Therefore, the use of three or more drugs to treat mycobacterial infections has become common. REF: 567 OBJ: Level 2: Interpretation 25. The Centers for Disease Control and Prevention (CDC) recommends all the following drugs for the treatment of Mycobacterium tuberculosis except: a. ethambutol. b. isoniazid. c. rifampin. d. ciprofloxacin. D The CDC currently recommends that, when isolated, M. tuberculosis be tested for susceptibility to isoniazid, rifampin, ethambutol, and streptomycin. REF: 586 OBJ: Level 1: Recall 26. What classifies an organism as a multidrug-resistant Mycobacterium tuberculosis? a. Organisms resistant to at least isoniazid and rifampin b. Organisms resistant to isoniazid, rifampin, ethambutol, and streptomycin c. Organisms resistant to streptomycin and rifampin d. Organisms resistant to ciprofloxacin and imipenem A Multidrug-resistant M. tuberculosis denotes the presence of M. tuberculosis resistant to at least isoniazid and rifampin. REF: 567 OBJ: Level 1: Recall 27. What is the antigen used in the purified protein derivative (PPD) skin test? a. A purified protein from the nucleus of Mycobacterium tuberculosis b. A purified piece of DNA from M. tuberculosis c. A purified protein from the cell wall of M. tuberculosis d. A piece of ribosomal RNA from M. tuberculosis C Purified protein derivative of the cell wall extracted from culture-grown M. tuberculosis is used as the antigen for the PPD test. REF: 587 OBJ: Level 1: Recall 28. A child visits his doctor because he has had a fever and a nonproductive cough. The child is also short of breath. The doctor orders a routine sputum culture and an acid-fast bacillus (AFB) culture and smear. The smear shows red organisms arranged in ropes. What is the most probable cause of this child’s fever and cough? a. Mycobacterium leprae b. M. avium c. M. intracellulare d. M. tuberculosis D Clinical diagnosis of primary tuberculosis is usually limited to signs and symptoms, and a positive tuberculin skin test. Children may demonstrate a nonproductive cough and fever with or without shortness of breath; these symptoms are unusual in adults. REF: 565 OBJ: Level 3: Synthesis 29. If a person has had tuberculosis during his or her lifetime, how likely is it that the person will get the disease again? a. 5% to 15% b. 20% to 25% c. 1% d. 50% A The risk of reactivation of tuberculosis is about 3.3% during the first year after a positive tuberculin skin test and a total of 5% to 15% thereafter. REF: 565 OBJ: Level 1: Recall 30. All of the following are common extrapulmonary infection sites for tuberculosis except: a. kidneys. b. gastrointestinal. c. liver. d. spleen. B The most common sites of spread of M. tuberculosis are the spleen, liver, lungs, bone marrow, kidney, adrenal gland, and eyes, usually in that order of occurrence. Other forms of extrapulmonary TB include pleural, lymphadenitis, gastrointestinal, skeletal, meningeal, peritoneal, and genitourinary infections. REF: 566 OBJ: Level 1: Recall 31. 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? a. Streptococcal pneumonia b. Primary atypical pneumonia c. Tuberculosis (TB) d. Pneumonia caused by gram-negative rods C The symptoms for TB include cough, fatigue, weight loss, low-grade fever, and night sweats. In 2011, the World Health Organization estimated that 12 million people worldwide suffered from TB. However, as many as one third of the world’s population might be harboring the bacteria. Currently, in the United States more cases are associated with foreign-born individuals from endemic areas than with U.S.–born persons. REF: 568 OBJ: Level 3: Synthesis 32. A patient with Hodgkin’s disease is feeling bad, so he pays a visit to 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? a. Mycobacterium tuberculosis b. M. avium c. M. gordonae d. M. haemophilum D The rare infections associated with M. haemophilum occur primarily in patients who are immunocompromised. Cases have been reported in patients with Hodgkin’s disease and acquired immunodeficiency syndrome (AIDS). Submandibular lymphadenitis, subcutaneous nodules, painful swellings, ulcers progressing to abscesses, and draining fistulas are often the clinical manifestations. REF: 569 OBJ: Level 3: Synthesis 33. 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? a. Hansen’s disease b. Extrapulmonary tuberculosis c. Non–Mycobacterium tuberculosis pulmonary disease d. M. xenopi A Patients with lepromatous leprosy do not produce an effective cell-mediated immune (CMI) response. Hansen’s 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. Despite its reputation, Hansen’s disease is not considered a highly contagious disease. REF: 572 OBJ: Level 3: Synthesis 34. A sputum culture from a patient in Texas has colonies that grow buff colored colonies in approximately 4 weeks. After exposure to light, the colonies turn intense yellow. This isolate is most likely: a. M. scrofulaceum. b. M. kansasii. c. M. fortuitum. d. M. xenopi. B Mycobacterium kansasii is second to MAC as the cause of NTM lung disease. In the United States, most cases of M. kansasii infections have been reported from the southern states of Texas, Louisiana, and Florida; from Illinois and Missouri in the Midwest; and from California. Colonies are photochromogenic, meaning that they form a pigment when exposed to light but are nonpigmented in the dark. REF: 568 OBJ: Level 3: Synthesis [Show More]

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