Tuberculosis Quiz

Tuberculosis (TB): Practice Guide for Exam-Style Questions

This guide breaks down the core concepts of Tuberculosis (TB) to help you prepare for exam questions. Focus on understanding the distinctions between latent and active disease, diagnostic methods, and treatment principles.

The Causative Agent: Mycobacterium tuberculosis

The primary cause of TB is Mycobacterium tuberculosis, an acid-fast bacillus. Its unique waxy cell wall, rich in mycolic acid, makes it resistant to many common antibiotics and disinfectants, which is a key reason for the lengthy treatment duration.

Transmission and Pathophysiology

TB is an airborne disease, transmitted via inhalation of respiratory droplets from a person with active pulmonary TB. Once inhaled, the bacteria are phagocytosed by alveolar macrophages, where they can multiply. The body’s cell-mediated immune response typically contains the infection within granulomas, leading to a latent state.

Latent TB Infection (LTBI) vs. Active TB Disease

This is a critical distinction for any exam. In LTBI, the person is infected, but bacteria are dormant and contained by the immune system. They are asymptomatic and non-contagious. In active TB disease, the immune system fails to contain the bacteria, leading to multiplication, symptoms, and potential transmission.

Key Symptoms of Pulmonary TB

Recognizing the classic symptoms is essential. A persistent cough lasting three weeks or more is the hallmark. Other key signs include fever, unintentional weight loss, night sweats, fatigue, chest pain, and hemoptysis (coughing up blood). These symptoms are often insidious in onset.

• Persistent cough (>3 weeks)
• Fever and chills
• Night sweats
• Unexplained weight loss (consumption)
• Fatigue or malaise
• Chest pain (pleurisy)
• Hemoptysis (coughing up blood)

Diagnostic Methods: From TST to IGRA

Diagnosis involves several steps. The Tuberculin Skin Test (TST or Mantoux) and Interferon-Gamma Release Assays (IGRAs) are used to screen for infection (both latent and active). A positive result from either test indicates TB infection but does not confirm active disease. A definitive diagnosis of active pulmonary TB requires a chest X-ray and bacteriological confirmation via sputum smear microscopy or culture.

Standard Treatment Regimens

The standard treatment for drug-susceptible active TB is a 6-month regimen of four first-line drugs: Isoniazid (INH), Rifampicin (RIF), Pyrazinamide (PZA), and Ethambutol (EMB). The first two months (intensive phase) use all four drugs, followed by four months (continuation phase) of INH and RIF. Non-adherence is a major cause of treatment failure and drug resistance.

Understanding Drug-Resistant TB (MDR-TB)

Multi-Drug Resistant TB (MDR-TB) is defined as resistance to at least Isoniazid and Rifampicin, the two most powerful anti-TB drugs. It arises from improper treatment, including non-adherence or incorrect prescribing. Treatment for MDR-TB is longer, more expensive, and involves more toxic second-line drugs.

The Role of the BCG Vaccine

The Bacillus Calmette-Guérin (BCG) vaccine is widely used in countries with high TB prevalence. Its primary value is in preventing severe, disseminated forms of TB in young children, such as TB meningitis. It offers limited and variable protection against adult pulmonary TB and can cause a false-positive TST result.

• Given at birth in high-prevalence countries.
• Protects infants/children from severe TB forms (meningitis, miliary TB).
• Does not reliably prevent primary infection or adult pulmonary TB.
• Can cause a false-positive reaction to the Tuberculin Skin Test (TST).
• Not routinely recommended in low-prevalence countries like the U.S.

Key Takeaways

• TB is caused by the airborne bacterium Mycobacterium tuberculosis.
• Latent TB Infection (LTBI) is asymptomatic and non-contagious; active TB disease is symptomatic and can be contagious.
• The hallmark symptom of active pulmonary TB is a persistent cough lasting over three weeks.
• Standard treatment for drug-susceptible TB is a 6-month, four-drug regimen (RIPE).
• MDR-TB is resistant to the two most effective drugs (Isoniazid and Rifampicin) and requires complex, prolonged treatment.

This content is for informational and educational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition.