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Ch. 24 - Microbial Diseases of the Respiratory System
Tortora - Microbiology: An Introduction 14th Edition
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
All textbooksTortora 14th EditionCh. 24 - Microbial Diseases of the Respiratory SystemProblem 8
Chapter 24, Problem 8

Briefly describe the procedures and positive results of the tuberculin test and what is indicated by a positive test.

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Understand that the tuberculin test, also known as the Mantoux test, is used to detect whether a person has been exposed to Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB).
The procedure involves intradermally injecting a small amount of purified protein derivative (PPD) tuberculin into the skin, usually on the forearm.
After 48 to 72 hours, the injection site is examined for a reaction, specifically looking for induration (a raised, hardened area) rather than redness alone.
A positive test is indicated by the presence of a measurable induration, which is typically assessed in millimeters; the size considered positive depends on the individual's risk factors and history.
A positive tuberculin test suggests that the person has been exposed to TB bacteria and has developed a cell-mediated immune response, but it does not distinguish between latent infection and active disease.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Tuberculin Test Procedure

The tuberculin test, also known as the Mantoux test, involves injecting a small amount of purified protein derivative (PPD) from Mycobacterium tuberculosis into the skin, usually on the forearm. After 48 to 72 hours, the injection site is examined for a reaction, which helps determine if the person has been exposed to the bacteria.
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Positive Test Results

A positive tuberculin test is indicated by a raised, firm swelling (induration) at the injection site, typically measured in millimeters. The size of the induration considered positive varies based on risk factors and patient history, reflecting an immune response to the tuberculin antigen.
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Interpretation and Significance of a Positive Test

A positive tuberculin test suggests prior exposure to Mycobacterium tuberculosis or vaccination with BCG, indicating latent or active tuberculosis infection. It does not differentiate between active disease and latent infection, so further clinical evaluation and tests are necessary for diagnosis.
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Related Practice
Textbook Question

Match the following choices to the statement in the question given below:

a. Bordetella pertussis

b. Corynebacterium diphtheriae

c. Legionella pneumophila

d. Mycobacterium tuberculosis

e. None of the above

Causes the formation of a membrane across the throat.

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Textbook Question

List the causative agent, mode of transmission, and endemic area for the diseases histoplasmosis, coccidioidomycosis, blastomycosis, and Pneumocystis pneumonia.

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Textbook Question

Identify the bacteria involved in respiratory infections using the following laboratory test results:

Gram-positive cocci

Catalase-positive: a. ____________________________________

Catalase-negative

Beta-hemolytic, bacitracin inhibition: b. ____________________________________

Alpha-hemolytic, optochin inhibition: c. ____________________________________

Gram-positive rods

Non-acid-fast: d. ____________________________________

Acid-fast: e. ____________________________________

Gram-negative cocci: f. ____________________________________

Gram-negative rods

Aerobes

Coccobacilli: g. ____________________________________

Rods

Grow on nutrient agar: h. ____________________________________

Require special media: i. ____________________________________

Facultative anaerobes

Coccobacilli: j. ____________________________________

Intracellular parasites

Form elementary bodies: k. ____________________________________

Do not form elementary bodies: l. ____________________________________

Wall-less: m. ____________________________________

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Textbook Question

In San Francisco, ten animal health care technicians developed pneumonia 2 weeks after 130 goats were moved to the animal shelter where they worked. Which of the following is false?

a. Diagnosis is made by a blood agar culture of sputum.

b. The cause is Coxiella burnetii.

c. The bacteria produce endospores.

d. The disease was transmitted by aerosols.

e. Diagnosis is made by complement-fixation tests for antibodies.

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Textbook Question

Which of the following leads to all the rest?

a. Catarrhal stage

b. Cough

c. Loss of cilia

d. Mucus accumulation

e. Tracheal cytotoxin

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Textbook Question

Match the following choices to the culture descriptions in questions 3 through 6:

a. Chlamydia

b. Coccidioides

c. Histoplasma

d. Mycobacterium

e. Mycoplasma

Microscopic examination of a lung biopsy shows spherules.

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