Deck 42: Mycobacteria

Question 1

What quantity of CSF is considered sufficient for detection of tuberculous meningitis?

A)10 mL
B)5 mL
C)1 mL
D)20 mL

Answer 1

A
Sufficient quantity of specimen is most critical for isolation of acid-fast bacilli from cerebrospinal fluid (CSF). There may be very few organisms in the spinal fluid, which makes their detection difficult. At least 10 mL of CSF is recommended for recovery of mycobacteria.

Question 2

The primary reservoir of the mycobacterium responsible for leprosy is

A)infected humans.
B)infected animals.
C)contaminated food.
D)contaminated objects.

Answer 2

A
The primary reservoir is infected humans. Transmission of leprosy occurs person to person through inhalation or contact with infected skin. It appears that inhalation of M. leprae discharged in nasal secretions of an infected individual is the more important mode of transmission.

Question 3

The most commonly isolated mycobacterium in the United States is

A)M.tuberculosis.
B)M.bovis.
C)M.avium- intracellulare.
D)M.paratuberculosis.

Answer 3

C
M. avium complex (MAC) is an important pathogen in immunocompromised and immunocompetent populations. This agent is among the most commonly isolated NTM species in the United States, particularly in its potentially pathogenic role in pulmonary infections in patients with acquired immunodeficiency syndrome (AIDS) and non-HIV-infected patients.

Question 4

M.fortuitum, M.chelonae, and M.abscessus are

A)responsible for approximately 90% of clinical mycobacterial disease.
B)able to grow on routine bacteriologic media.
C)weakly gram-positive rods resembling diphtheroids on Gram stain.
D)seen as visible colonies that appear on solid media in 7 days or less.
E)All of the above are correct.

Question 5

The specimen of choice for detecting urinary tract mycobacterial disease is

A)a single clean-catch midstream urine sample.
B)a 24-hour timed urine sample.
C)three daily clean-catch midstream urine samples.
D)a biopsy of the suspected site.

Question 6

Slow-growing nontuberculous mycobacteria whose colonies become pigmented when exposed to light are referred to as

A)scotochromogens.
B)photochromogens.
C)nonphotochromogens.
D)chromogenicums.

Question 7

A positive tuberculin skin test, or PPD test, is characterized by

A)erythema and induration.
B)redness and rash.
C)swelling and erythema.
D)edema and rash.

Question 8

Slow-growing nontuberculous mycobacteria whose colonies are pigmented when grown in the dark or the light are referred to as

A)scotochromogens.
B)photochromogens.
C)nonphotochromogens.
D)chromogenicums.

Question 9

The specimen of choice for detecting mycobacterium in a skin lesion or wound is

A)a swab placed in transport medium, such as Amie's or Stuart's.
B)a needle aspirate.
C)a skin scraping.
D)a swab placed in anaerobic conditions.

Question 10

The specimen of choice for detecting tuberculous pulmonary mycobacterial disease is

A)spontaneously produced sputum.
B)gastric lavage.
C)transtracheal aspiration.
D)bronchoscopy.

Question 11

The tuberculin skin test, or PPD test, is based on

A)delayed hypersensitivity cell-mediated immunity to certain antigenic components of the organism.
B)injection of M.tuberculosis under the skin and subsequent mild cutaneous infection.
C)antigen-antibody reactions occurring at the injection site.
D)All of the above are correct.

Question 12

Of the following species of mycobacterium, which causes a chronic disease of the skin, mucous membranes, and nerve tissue and has not yet been cultivated in vitro?

A)M.paratuberculosis
B)M.lepraemurium
C)M.phlei
D)M.leprae

Question 13

The specimen of choice for detecting nontuberculous pulmonary mycobacterial disease is

A)spontaneously produced sputum.
B)gastric lavage.
C)transtracheal aspiration.
D)bronchial lavages, washings, and brushings.

Question 14

Slow-growing nontuberculous mycobacteria whose colonies produce no pigment whether they are grown in the dark or the light are referred to as

A)scotochromogens.
B)photochromogens.
C)nonphotochromogens.
D)chromogenicums.

Question 15

The recent emergence of epidemic multidrug-resistant strains of M.tuberculosis in conjunction with the ending of the downward trend of reported cases of tuberculosis in the United States has been largely attributed to

A)the HIV epidemic.
B)ineffective treatment regimens.
C)political factors.
D)shortened treatment regimens.
E)All of the above are correct.

Question 16

The mycobacterial species that occur in humans and belong to the M.tuberculosis complex include

A)M.tuberculosis, nontuberculous mycobacteria, M.bovis, and M.africanum.
B)M.tuberculosis, M.gordonae, M.bovis BCG, and M.africanum.
C)M.tuberculosis, M.bovis, M.avium, and M.intracellulare.
D)M.tuberculosis, M.bovis, M.bovis BCG, and M.africanum.

Question 17

The Runyon system of classification is based on

A)colony and microscopic morphology.
B)biochemical characteristics.
C)growth rate and colonial pigmentation.
D)All of the above are correct.

Question 18

Known to cause an inflammatory bowel disease referred to as Johne's disease in cattle, sheep, and goats, this organism has been isolated from the bowel mucosa of patients with Crohn's disease.

A)M.paratuberculosis
B)M.avium-intracellulare
C)M.phlei
D)M.lepraemurium

Question 19

Characteristics that are found in the bacteria called Mycobacterium are

A)a cell wall that contains N-glycolylmuramic acid and a very high lipid content.
B)resists staining with commonly used basic aniline dyes.
C)resist decolorization by acidified alcohol.
D)slow growth as compared to most other human pathogenic bacteria.
E)All of the above are correct.

Question 20

The term complex as used in "M.tuberculosis complex"

A)means that the identification of the organism is complex and is only done in very large reference laboratories.
B)is used to describe two or more species whose distinction is complicated and of little or no medical importance.
C)refers to a set of organisms that are genetically indistinguishable but that are phenotypically different.
D)All of the above are correct.

Question 21

The fluorochrome method of staining Mycobacterium

A)is more sensitive than the conventional carbolfuchsin stains.
B)enables the smear to be initially examined at lower magnifications.
C)results in a higher yield of positive smears.
D)will substantially reduce the amount of time needed for examining smears.
E)All of the above are correct.

Question 22

Negative mycobacterial cultures are reported final, and the cultures are discarded after what period of time?

A)7 days
B)2 weeks
C)4 weeks
D)8 weeks

Question 23

The first test that is always performed on organisms growing on solid or liquid mycobacterial media is

A)the niacin test.
B)an acid-fast stain.
C)a Gram stain.
D)a broth test.

Question 24

To inoculate test media, such as biochemical tests and pigmentation and growth rate determinations, the laboratorian would

A)use a broth subculture or the primary liquid culture.
B)use isolated colonies from the primary solid medium.
C)subculture from primary media to solid media and work from those subcultures.
D)swab the growth on the primary solid medium.

Question 25

Under what circumstance might slow-growing mycobacteria appear to produce colonies in a few days?

A)When the inoculum is too heavy
B)When subcultured to enriched medium
C)When incubated at slightly warmer temperatures
D)When kept in the light

Question 26

The stain that requires heating the slide for better penetration of stain into the mycobacterial cell wall is known as the

A)Kinyoun.
B)Ziehl-Neelsen.
C)fluorochrome.
D)carbolfuchsin.
E)All of the above are correct.

Question 27

Optimal conditions for recovery of M.haemophilum from specimens include

A)inoculation to a chocolate agar plate.
B)incubation at 25° to 33°C.
C)placement of an X-factor disk on the media.
D)5% to 10% carbon dioxide and high humidity.
E)All of the above are correct.

Question 28

Acid-fast smears should be examined carefully by scanning at least how many oil immersion fields?

A)100
B)200
C)300
D)400

Question 29

The presence of what in CSF is thought to be diagnostic of tuberculous meningitis?

A)Mononuclear leukocytes and acid-fast bacilli
B)Acid-fast bacilli
C)Tuberculostearic acid
D)Increased protein and decreased glucose
E)All of the above are correct.

Question 30

The stain that does not require heating the slide for better penetration of stain into the mycobacterial cell wall is known as the

A)Kinyoun.
B)Ziehl-Neelsen.
C)immunofluorochrome.
D)carbolfuchsin.
E)All of the above are correct.

Question 31

Specimens for Mycobacterium studies that require concentration, decontamination, or liquefaction include

A)CSF and other body fluids.
B)sputum.
C)urine.
D)swabs and wound aspirates.
E)All of the above are correct.

Question 32

On Gram stain, mycobacteria appear as

A)slender, well-stained gram-positive bacilli.
B)poorly stained, beaded, gram-positive bacilli.
C)gram-variable to gram-positive bacilli.
D)partially invisible gram-negative bacilli.

Question 33

The nonpathogenic Mycobacterium commonly found in tap water, which has been a problem when tap water or deionized water has been used in the preparation of smears, is

A)M.paratuberculosis.
B)M.lepraemurium.
C)M.phlei.
D)M.gordonae.

Question 34

Sodium hydroxide, Zephiran-trisodium phosphate, N-acetyl-L-cysteine-NaOH, and oxalic acid are associated with

A)methods of cultivating mycobacterium in vitro.
B)digestion and decontamination of specimens for mycobacterial studies.
C)identification of clinically significant Mycobacterium.
D)antimicrobial susceptibility testing of mycobacterial species.

Question 35

In identification of mycobacterial isolates, the niacin test involves

A)the accumulation of niacin in the medium in which the organism is growing.
B)the metabolism of niacin to nicotinic acid by enzymatic action.
C)testing the isolate for susceptibility to niacin.
D)utilization of niacin in metabolic pathways to produce nicotinic acid.

Question 36

The type of specimen collected for mycobacterial studies that must be neutralized with 10% sodium carbonate is

A)spontaneously produced sputum.
B)gastric lavage.
C)transtracheal aspiration.
D)bronchial lavage.

Question 37

For reliable results, the niacin test should be

A)performed only from cultures on L-J that are at least 2 weeks old and show at least five colonies.
B)performed only from cultures on L-J that are at least 3 weeks old and show at least 50 colonies.
C)performed only from cultures on 7H11 agar that are at least 3 weeks old and show at least 50 colonies.
D)performed only from cultures on 7H11 agar that are at least 2 weeks old and show at least five colonies.

Question 38

Optimal conditions for most mycobacterial cultures are

A)25° to 30° C in the dark in an atmosphere of 2% carbon dioxide and high humidity.
B)35° C in the dark in an atmosphere of 5% to 10% carbon dioxide and high humidity.
C)35° C in the dark in a microaerophilic atmosphere of 10% carbon dioxide and high humidity.
D)32° C in the dark in an atmosphere of decreased carbon dioxide and increased humidity.

Question 39

One drawback associated with the fluorochrome stain method for detecting Mycobacterium is that

A)it is less sensitive than the conventional carbolfuchsin stains.
B)it requires the smear to be initially examined at lower magnifications.
C)many rapid-growers may not appear fluorescent with these reagents.
D)it increases the amount of time needed for examining smears.

Question 40

When culturing for Mycobacterium, rapid-growers usually produce colonies within how many days after subculture?

A)At least 7 days
B)Longer than 7 days
C)3 to 4 days
D)2 to 3 days

Question 41

The system of classification based on growth rate and colonial pigmentation is called

A)Bergey's.
B)scotochromogenic.
C)Runyon.
D)carotenoid.

Question 42

Large numbers of a poorly stained, beaded, gram-positive bacilli in a sputum specimen might be which bacterium?

A)Klebsiella pneumoniae
B)Mycobacterium spp.
C)Streptococcus pneumonia
D)Actinomyces spp.

Question 43

The fluorochrome method of staining Mycobacterium

A)is less sensitive than the conventional carbolfuchsin stains.
B)enables the smear to be initially examined at lower magnifications.
C)results in a lower yield of positive smears.
D)will substantially increase the amount of time needed for examining smears.
E)All of the above are correct.

Question 44

Photochromogens can be described as are referred to as

A)slow-growing nontuberculous mycobacteria whose colonies become pigmented when exposed to light.
B)slow-growing nontuberculous mycobacteria whose colonies are pigmented when grown in the dark or the light.
C)slow-growing nontuberculous mycobacteria whose colonies produce no pigment whether they are grown in the dark or the light.
D)slow-growing tuberculous mycobacteria whose colonies become pigmented when exposed to light.

Question 45

A cell wall that contains N-glycolylmuramic acid and a very high lipid content is a characteristics that is found in which bacteria?

A)Fungi
B)Klebsiella
C)Mycobacterium
D)Enterobacteriaceae

Question 46

The 3-day test that is useful for identifying the rapid-growers M.fortuitum and M.chelonae and that measures the rate by which this enzyme breaks down phenolphthalein disulfate into phenolphthalein and other salts is

A)the niacin test.
B)the phenolphthalein test.
C)the arylsulfatase test.
D)the Tween 80 test.

Question 47

In identification of mycobacterial isolates, the Tween 80 test involves

A)an enzyme that is able to produce Tween 80 from certain ingredients found in the medium.
B)a lipase that is able to hydrolyze polyoxyethylene sorbitan monooleate into oleic acid and polyoxyethylated sorbitol.
C)the metabolism of niacin to nicotinic acid by enzymatic action.
D)testing the isolate for susceptibility to Tween 80.

Question 48

In identification of mycobacterial isolates, the catalase test involves

A)the enzyme catalase, which splits hydrogen peroxide into water and oxygen.
B)measuring the height of a column of bubbles of oxygen.
C)the ability of the catalase enzyme to remain active after heating.
D)not the presence of, but the relative activity of the catalase enzyme.
E)All of the above are correct.