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Questions and Answers
Which method is commonly used to assess the toxigenicity of bacteria?
Which method is commonly used to assess the toxigenicity of bacteria?
Which biomarker may indicate a worse prognosis in a patient?
Which biomarker may indicate a worse prognosis in a patient?
Which of the following conditions closely mimics Corynebacterium diphtheria?
Which of the following conditions closely mimics Corynebacterium diphtheria?
Who is at increased risk for contracting diphtheria?
Who is at increased risk for contracting diphtheria?
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What is the primary method of preventing diphtheria?
What is the primary method of preventing diphtheria?
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What is the primary agent responsible for causing tuberculosis?
What is the primary agent responsible for causing tuberculosis?
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Which of the following symptoms is NOT typically associated with active tuberculosis?
Which of the following symptoms is NOT typically associated with active tuberculosis?
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What is the characteristic structure of the cell wall of Mycobacterium species?
What is the characteristic structure of the cell wall of Mycobacterium species?
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How long does the cell division of Mycobacterium tuberculosis take?
How long does the cell division of Mycobacterium tuberculosis take?
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What is the primary symptom associated with diphtheria?
What is the primary symptom associated with diphtheria?
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What role does mycolic acid play in Mycobacterium tuberculosis?
What role does mycolic acid play in Mycobacterium tuberculosis?
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Which fragment of the diphtheria toxin is responsible for inhibiting protein synthesis?
Which fragment of the diphtheria toxin is responsible for inhibiting protein synthesis?
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Which of the following antibiotics is NOT typically used in the treatment of tuberculosis?
Which of the following antibiotics is NOT typically used in the treatment of tuberculosis?
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What type of bacteria is Corynebacterium diphtheriae?
What type of bacteria is Corynebacterium diphtheriae?
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What is the main reason for the use of multiple antimicrobial drugs in tuberculosis treatment?
What is the main reason for the use of multiple antimicrobial drugs in tuberculosis treatment?
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Which of the following substances is particularly required for the growth of Corynebacterium diphtheriae?
Which of the following substances is particularly required for the growth of Corynebacterium diphtheriae?
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Which diagnostic method is most commonly used for identifying tuberculosis?
Which diagnostic method is most commonly used for identifying tuberculosis?
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What characterizes toxigenic strains of Corynebacterium diphtheriae?
What characterizes toxigenic strains of Corynebacterium diphtheriae?
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What are the biotypes of Corynebacterium diphtheriae based on?
What are the biotypes of Corynebacterium diphtheriae based on?
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How does diphtheria toxin affect eukaryotic cells?
How does diphtheria toxin affect eukaryotic cells?
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What is the purpose of immunization with diphtheria toxoid?
What is the purpose of immunization with diphtheria toxoid?
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What is a primary factor limiting patient compliance with tuberculosis treatment?
What is a primary factor limiting patient compliance with tuberculosis treatment?
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What does MDR-TB stand for?
What does MDR-TB stand for?
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Which of the following conditions is NOT caused by systemic miliary tuberculosis?
Which of the following conditions is NOT caused by systemic miliary tuberculosis?
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What is the primary virulence factor of Mycobacterium tuberculosis?
What is the primary virulence factor of Mycobacterium tuberculosis?
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Why is the BCG vaccine not widely used in the United States?
Why is the BCG vaccine not widely used in the United States?
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What is the role of directly observed therapy (DOT) in tuberculosis treatment?
What is the role of directly observed therapy (DOT) in tuberculosis treatment?
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What type of organism is Mycobacterium leprae?
What type of organism is Mycobacterium leprae?
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What is a common factor affecting the clinical course of leprosy?
What is a common factor affecting the clinical course of leprosy?
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Study Notes
Mycobacterium tuberculosis
- Mycobacterium tuberculosis is a slow-growing, aerobic, acid-fast bacterium that causes tuberculosis.
- Tuberculosis is a chronic, progressive infection that primarily affects the lungs.
- M. tuberculosis is a weakly gram-positive, non-motile, rod-shaped bacterium.
- It is an obligate aerobe and a facultative intracellular parasite. This explains why tuberculosis typically affects the lungs.
- The cell wall of mycobacterium is primarily composed of lipids. The lipid layer makes it impervious to gram staining, resulting in a variable gram reaction.
- M. tuberculosis has a slow generation time (18-24 hours) due to the mycolic acid layer in its cell wall, which inhibits nutrient diffusion and protects it from immune cells.
- Symptoms of active TB include: coughing (lasting more than 3 weeks), coughing up blood, chest pain, unintentional weight loss, fatigue, fever, night sweats, chills, and loss of appetite.
- Antibiotic treatment involves a combination therapy with isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), ethambutol (EMB), or streptomycin (SM) for at least 4 months.
- Treatment of M. tuberculosis can be challenging due to its slow growth rate, the long treatment duration (6-9 months), and potential side effects of the antibiotics.
- Directly observed therapy (DOT) is used to ensure patient compliance.
- Antibiotic resistance is a concern, with multi-drug resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) strains emerging.
- A BCG vaccine is available but is not particularly effective and is not used in the United States.
- M. tuberculosis does not produce toxins or exoenzymes that damage tissue. The protective waxes in the cell wall are its primary virulence factor.
- Damage caused by tuberculosis stems from the immune response to the bacteria.
- Systemic miliary tuberculosis can spread causing: meningitis, sterile pyuria, Pott's disease (spinal tuberculosis), Addison's disease, hepatitis, and lymphadenitis.
Mycobacterium leprae
- Mycobacterium leprae and Mycobacterium lepromatosis cause leprosy.
- Leprosy is an obligate intracellular organism that parasitizes histiocytes (skin macrophages) and Schwann cells in the peripheral nerves.
- Multidrug therapy is available for treating leprosy, but some patients experience relapses or prolonged symptoms.
- Immune responses to bacterial components influence the range of symptoms.
Corynebacterium diphtheriae
- Corynebacterium diphtheriae infects the nasopharynx or skin.
- Toxigenic strains produce a potent exotoxin causing diphtheria.
- Diphtheria symptoms include pharyngitis, fever, swelling of the neck or skin lesion.
- Diphtheritic lesions are covered by a pseudomembrane.
- The toxin can spread through the circulatory system, impacting distant organs and leading to paralysis and congestive heart failure.
- Corynebacterium diphtheriae is a nonmotile, noncapsulated, club-shaped, gram-positive bacillus.
- Toxigenic strains are lysogenic for corynebacteriophages carrying the gene for diphtheria toxin.
- C. diphtheriae biotypes include mitis, intermedius, and gravis, classified based on colony morphology and lysotype.
- Optimal diphtheria toxin production requires a medium supplemented with amino acids and low iron content.
- Asymptomatic nasopharyngeal carriage is common in endemic regions.
- In susceptible individuals, toxigenic strains multiply and secrete diphtheria toxin in nasopharyngeal or skin lesions.
- The diphtheritic lesion is often covered by a pseudomembrane.
- Diphtheria toxin is cleaved into two fragments: Fragment A (catalytic domain) and Fragment B (transmembrane and receptor binding domains).
- Fragment A inhibits protein synthesis in eukaryotic cells by ADP-ribosylation of elongation factor 2.
- Fragment B binds to cell surface receptors to deliver Fragment A to the cytosol.
- Protection against diphtheria involves antibody responses to diphtheria toxin or toxoid (formaldehyde-inactivated toxin).
- Diagnosis relies on culture-proven toxigenic C. diphtheriae infection in the skin, nose, or throat, and clinical signs of nasopharyngeal diphtheria.
- Toxigenicity is identified by in vitro or in vivo methods.
- Elevated biomarkers like total leukocyte count and serum glutamic oxalo-acetic transaminase levels (SGOT) can indicate a worse prognosis and correlate with disease severity.
- Corynebacterium diphtheria has many similarities with other diseases, such as viral pharyngitis, streptococcal pharyngitis, acute epiglottitis, infectious mononucleosis, oral candidiasis, infective endocarditis, angioedema, epiglottitis, and retropharyngeal abscess.
- Risk of diphtheria is higher in unvaccinated children and adults, people living in crowded conditions, and people travelling to areas with high diphtheria prevalence.
- Antibiotics like penicillin or erythromycin help clear up infections.
- Antitoxin is used to counteract diphtheria toxin in the body.
- Immunization with diphtheria toxoid is highly effective.
- Diphtheria patients require prompt treatment with antitoxin to neutralize circulating toxin.
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Description
This quiz explores the characteristics, symptoms, and treatment of Mycobacterium tuberculosis, the bacterium responsible for tuberculosis. It covers the bacterium's biology, including its classification as a slow-growing and aerobic microorganism, and the impact of its lipid-rich cell wall on antibiotic resistance. Test your knowledge on this significant public health issue.
