Lecture 11: Tuberculosis

What is the causative agent of human tuberculosis?

Mycobacterium tuberculosis

What type of bacteria is M. tuberculosis?

Aerobic, acid-fast, non-spore forming, non-motile, Gram-positive rods

How long can it take for M. tuberculosis to grow in culture?

Weeks to months

What is the characteristic staining method for M. tuberculosis?

Acid-fast staining

How does M. tuberculosis respond to heat and chemical agents?

Readily killed by heat, but resistant to chemical agents and drying

What was the death rate from tuberculosis in the early 1800s in the US and Europe?

Approaching 1%

What significant drug was introduced in 1948 to combat tuberculosis?

Streptomycin

How many people are currently infected with tuberculosis worldwide?

2 billion people

What percentage of tuberculosis cases and deaths occur in resource-poor countries?

95%

What are the three possible outcomes of a tuberculosis infection?

Eradication, latent infection, acute disease

What is a latent tuberculosis infection?

The organism is contained in a structure called a tubercle, usually not visible on X-ray unless calcified

What is the most common form of acute tuberculosis disease?

Miliary tuberculosis

What are common clinical signs of miliary tuberculosis?

Anorexia, fever, cough, weight loss, respiratory symptoms

What is the mortality rate for tuberculosis meningitis?

Can be as high as 50%

What is the typical duration of symptoms for abdominal tuberculosis?

1-2 weeks

What are common clinical signs of pulmonary tuberculosis?

Fever, cough (often with bloody sputum), malaise, anorexia

What traditional diagnostic method is commonly used for tuberculosis?

Acid-fast staining of sputum or biopsy samples

What is the BCG vaccine?

A vaccine using an avirulent strain of Mycobacterium bovis, available in endemic areas

What is multidrug-resistant tuberculosis (MDR)?

Resistance to rifampicin and isoniazid

What is extensively drug-resistant tuberculosis (XDR)?

Resistance to isoniazid, rifampicin, any fluoroquinolone, and at least one of three injectable second-line drugs

What factors contributed to the increase in MDR tuberculosis cases in the 1990s?

Outbreaks in vulnerable populations such as the homeless, HIV+, and incarcerated individuals

What are the mechanisms of drug resistance in tuberculosis?

Acquired resistance, amplified resistance, and transmitted resistance