L-30 : Antimycobacterial Agents Mycobacteria and Tuberculosis Quiz

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Questions and Answers

What property of mycobacteria is primarily responsible for their acid-fast characteristic?

The presence of a capsule made of polysaccharides.

The presence of a peptidoglycan layer in their cell wall.

The abundance of mycolic acids in their cell walls. (correct)

The high concentration of teichoic acids on their surface.

Which statement best describes the growth requirements of Mycobacterium tuberculosis?

It requires specific media such as Lowenstein-Jensen supplemented with malachite green. (correct)

It can be easily cultured in any standard bacteriological medium.

It can only grow in anaerobic conditions.

It is an obligate anaerobe and cannot be grown in lab cultures.

What characteristic distinguishes XDR tuberculosis from MDR tuberculosis?

XDR is only resistant to three specific second-line drugs, whereas MDR is resistant to all second-line drugs.

XDR has resistance to fluoroquinolones and at least one injectable second-line drug, whereas MDR is only resistant to isoniazid and rifampin. (correct)

XDR is easily treated with first-line antibiotics, while MDR requires second-line agents.

XDR shows resistance to isoniazid and rifampin but is susceptible to fluoroquinolones.

Which of the following is NOT a typical species of mycobacteria associated with disseminated infections?

Mycobacterium leprae (C) Signup and view all the answers

Why are treatments for mycobacterial infections, such as those caused by M. tuberculosis, M. leprae, and M. avium-intracellulare, often complicated?

Limited knowledge about mechanisms of resistance, intracellular location and advancement of the disease makes treatment complex. (D) Signup and view all the answers

What is the primary reason for the development of Multidrug-Resistant Tuberculosis (MDR TB)?

Inadequate patient compliance during the use of first-line anti-TB medications. (A) Signup and view all the answers

What specific feature of mycobacteria is responsible for the staining process where the bacteria retain carbolfuchsin stain after acid wash?

The presence of mycolic acids on their cell wall. (A) Signup and view all the answers

Which adverse effect is the most prominent when using fatty acid synthetase inhibitors?

Hepatic dysfunction (B) Signup and view all the answers

Which of the following describes Thiacetazone's usage and availability?

Available worldwide but contraindicated in HIV patients. (C) Signup and view all the answers

What is the primary reason Amikacin and Kanamycin are utilized?

To treat infections caused by multidrug-resistant mycobacterial strains. (C) Signup and view all the answers

What common side effect is associated with Cycloserine?

Restlessness and CNS disorders (C) Signup and view all the answers

Which drug is considered a protein synthesis inhibitor and is associated with significant nephrotoxicity in drug-resistant tuberculosis?

Capreomycin (C) Signup and view all the answers

Which of the following best describes the primary challenge in treating extensively drug-resistant tuberculosis (XDR TB)?

The limited efficacy of available second-line drug options. (A) Signup and view all the answers

Directly Observed Therapy (DOT) is primarily used in tuberculosis treatment to:

Ensure patients fully adhere to their prescribed medication schedules. (B) Signup and view all the answers

Which of the following is NOT considered a first-line drug (FLD) in the treatment of tuberculosis?

Ciprofloxacin (C) Signup and view all the answers

Why is Streptomycin classified as a second-line drug in many parts of the world, despite its historical use?

The increasing prevalence of resistance coupled and injection requirement with potential nephrotoxicity issues. (A) Signup and view all the answers

When do patient need to have DOT (Direct Observation Therapy) for treatment of tuberculosis?

For all tuberculosis patients as a preferred core management strategy. (C) Signup and view all the answers

What is the most probable reason why patients receiving treatment for tuberculosis may find it difficult to remain compliant?

The significant adverse effects of some medications. (C) Signup and view all the answers

Which of these first-line drugs has a specific contraindication related to patients taking retroviral drugs?

Rifampin (C) Signup and view all the answers

Which of the following is considered an essential first-line drug (FLD) in the RIPE regimen for tuberculosis treatment?

Pyrazinamide (B) Signup and view all the answers

What is a primary reason why some less frequently used drugs are categorized as second-line, even if they are effective against TB?

As a result of a higher prevalence of resistance, significant adverse effects, or difficulty of administration. (C) Signup and view all the answers

Which of the following is the most common adverse effect associated with Rifampin?

Gastrointestinal upset (B) Signup and view all the answers

What is the primary mechanism by which Rifampin inhibits bacterial growth?

By blocking bacterial RNA synthesis (A) Signup and view all the answers

In what patient population does Isoniazid-induced hepatotoxicity increase?

Older patients (A) Signup and view all the answers

What specific genetic mutation leads to Rifampin resistance in Mycobacteria?

Mutations in the rpoB gene (A) Signup and view all the answers

Which of the following conditions can be alleviated using Pyridoxine when taking Isoniazid?

Peripheral neuropathy (A) Signup and view all the answers

Besides tuberculosis, Rifampin is also used prophylactically in which of the following conditions?

Meningococcal and Staphylococcal carrier states (D) Signup and view all the answers

A patient on Rifampin therapy has orange-red discoloration of bodily fluids. What does this symptom indicate?

A common, expected symptom to monitor patient compliance (C) Signup and view all the answers

Which of the following is a rare adverse effect of Isoniazid?

Lupus-like syndrome (A) Signup and view all the answers

Which of these is NOT a characteristic of Rifampin?

It is primarily eliminated in urine (B) Signup and view all the answers

What is the clinical significance of Isoniazid being used in combination with Pyridoxine?

To prevent the development of peripheral neuropathy (C) Signup and view all the answers

Which of the following best describes the interaction between rifampin and protease inhibitors?

Rifampin decreases the concentration of protease inhibitors, making them sub-therapeutic, with protease inhibitors also leading to increased rifampin levels causing hepatotoxicity and GI toxicity. (C) Signup and view all the answers

What is a key distinction between rifapentine and rifampin concerning their usage?

Rifapentine is often a once-weekly treatment for tuberculosis, while rifampin is administered more frequently. (B) Signup and view all the answers

In what scenario is rifabutin primarily preferred over rifampin?

When patients cannot tolerate or have interactions with rifampin, or when treating MAI (C) Signup and view all the answers

What is the primary mechanism of action of ethambutol (EMB) in treating mycobacterial infections?

It disrupts arabinogalactan synthesis, and component on the cell wall. (C) Signup and view all the answers

Which of the following adverse effects is NOT associated with ethambutol (EMB) use?

Severe gastrointestinal upset characterized by severe diarrhea and vomiting (C) Signup and view all the answers

What is the mechanism of action of pyrazinamide (PZA) in the treatment of tuberculosis?

It is converted to pyrazinoic acid by pyrazinamidases and is thought to be similar to isoniazid in mechanism. (A) Signup and view all the answers

Why is pyrazinamide's spectrum considered narrow?

It is specific effectively only against M. tuberculosis strains. (B) Signup and view all the answers

Rifapentine, like rifampin, is contraindicated with protease inhibitors. What is the primary reason behind this contraindication?

Rifapentine reduces protease inhibitors’ effectiveness, while protease inhibitors increase rifapentine's toxicity. (C) Signup and view all the answers

Which statement best describes the use of rifabutin in anti-mycobacterial therapy?

It is primarily used in prevention of disseminated MAI infection and those unable to use rifampin. (A) Signup and view all the answers

What is unique about ethambutol's elimination from the body?

It is eliminated unchanged in the urine. (B) Signup and view all the answers

Study Notes

Anti-Mycobacterial Agents

Mycobacteria are aerobic, acid-fast bacilli or rods.
Mycobacteria are obligate aerobes, meaning they require oxygen for survival.
Mycobacteria retain carbolfuchsin stain due to a high lipid content (60%) in their cell walls.
The long-chain fatty acid mycolic acid (C70 to C90) contributes to acid-fastness.
Mycobacterium tuberculosis can be grown on specialized media like Lowenstein-Jensen media with malachite green.
Mycobacterium leprae cannot be grown on standard bacteriologic media.

Mycobacteria

Tuberculosis: Caused by M. tuberculosis
Leprosy: Caused by M. leprae
Disseminated infections: Caused by atypical mycobacteria such as M. avium, M. avium-intracellulare, M. ulcerans, rapidly growing mycobacteria- M. marinum, M. abscessus, M. haemophilum, M. xenopi, etc.

Tuberculosis

Transformation from MDR-TB (multidrug-resistant TB) to XDR-TB (extensively drug-resistant TB) is a major challenge.
XDR-TB arises from misuse of second-line drugs, while MDR-TB frequently stems from misuse of first-line drugs.
Therapy for M. tuberculosis, M. leprae, and M. avium-intracellulare infections is complicated by limited knowledge of mechanisms and drug resistance.
Intracellular infection location and disease progression can also complicate treatment.
MDR-TB is resistant to at least two first-line anti-TB drugs (isoniazid and rifampicin).
XDR-TB is resistant to isoniazid and rifampin, plus any fluoroquinolone and at least one injectable second-line drug (amikacin, kanamycin, or capreomycin).
Treatment options for XDR-TB are very limited and less effective, compared to those available for MDR-TB.

DOT (Direct Observation Therapy)

Directly observing patients take medications ensures adherence.
DOT is a preferred core management strategy for all tuberculosis patients. This is due to potential negative effects and patient struggles with medication compliance.

Drugs

First-line drugs (FLDs) are essential for TB treatment, including Isoniazid (INH), Rifampin, Ethambutol, and Pyrazinamide (PZA).
Many second-line drugs (SLDs) are available for MDR and XDR-TB. These include Amikacin, Ciprofloxacin, Ethionamide, p-Aminosalicylic acid, Capreomycin, Streptomycin, Cycloserine, and others.
Streptomycin is now considered a second-line drug due to increasing resistance.
Dosage guidelines for first- and second-line drugs are provided.

Isoniazid (INH)

Isoniazid is the most effective antituberculosis drug.
Isoniazid inhibits synthesis of mycolic acids in the cell wall.
Isoniazid is a broad-spectrum drug and is used as prophylaxis for patients who have tested positive for tuberculosis exposure.
Isoniazid is well tolerated by many patients but can cause adverse effects such as hepatoxicity, peripheral neuropathy, and hemolysis in patients with G-6-PD deficiency.

Rifampin (RIF)

Rifampin is a fat-soluble macrolide and inhibits bacterial RNA synthesis.
Rifampin turns body fluids red-orange.
Common adverse effects include gastrointestinal upset, hepatitis, liver dysfunction, and skin rashes.
Rifampin can decrease the concentration of other drugs and cause interactions with protease inhibitors when taken together.

Rifamycins (Rifapentine, Rifabutin)

Rifapentine and Rifabutin are alternatives to Rifampin that are often used to treat tuberculosis, particularly for patients on antiretroviral therapy.
Rifapentine is given once weekly, with a longer half-life compared to Rifampin.
Rifabutin is often used for patients who cannot tolerate rifampin due to drug interactions.

Ethambutol (EMB)

Ethambutol is a water-soluble drug that inhibits synthesis of arabinogalactan in mycobacterial cell walls.
Adverse effects include visual disturbances, such as optic neuritis.
Ethambutol is used in combination regimens for tuberculosis treatments

Pyrazinamide (PZA)

Pyrazinamide is a derivative of nicotinic acid that is bactericidal.
Pyrazinamide inhibits fatty acid synthetase.
Common adverse effects include hepatic dysfunction, polyarthralgia, hyperuricemia, myalgia, and photosensitivity.

Combinations

Rifamate (RIF + INH) and Rifater (RIF + INH + PZA) are common combination regimens for TB treatment.

Alternate Drugs:

Streptomycin, Thiacetazone, Amikacin, Kanamycin, Fluoroquinolones (Ciprofloxacin, Levofloxacin), Ethionamide, and Para-aminosalicylic acid (PAS) are used when resistance to first-line drugs occurs.

M. Leprae (Hansen's Disease) Drugs

Dapsone (and Acedapsone) and Clofazimine (Lamprene) are commonly used.
Dapsone is an effective drug against M. leprae, inhibiting bacterial folic acid synthesis.
Acedapsone is a repository form of dapsone, providing sustained release.
Clofazimine is another option and causes discoloration of the skin.

Atypical Mycobacterial Infections

Atypical mycobacterial infections are caused by various Mycobacterium species such as M. avium, M. avium-intracellulare, and M. ulcerans.
Common treatments include Erythromycin, Amikacin, Azithromycin, or Clarithromycin.
Infections with M. avium complex, or MAC, can be disseminated in AIDS patients.

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Description

Test your knowledge on mycobacteria and their unique characteristics, particularly focusing on Mycobacterium tuberculosis. This quiz covers growth requirements, resistance issues, and treatment complications associated with mycobacterial infections. Challenge yourself with questions about drug resistance and specific treatment details.