Pulmonary Tuberculosis

Where does tuberculosis come from? In 1882 the German microbiologist Robert Koch discovered the bacterial pathogen of TB: Mycobacterium tuberculosis (he received the Nobel Prize for Medicine in 1905). Today we know that TB is caused by various types of mycobacteria: Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium africanum, Mycobacterium microti are the most important ones (in descending order). Tuberculosis is a contagious disease, and is spread from person to person via droplet infection.

Tuberculosis infections began to increase again in 1985, linked to HIV. As a consequence of the weakened immune system, HIV positive people are more likely to get TB and progress from latent to active TB. In 2019, about 1.4 million people died from tuberculosis worldwide.

What about the bacteria Mycobacterium tuberculosis? Sample material is sputum. Mycobacterium tuberculosis grows aerobically, divides extremely slowly (every 18–24 hours) and can survive in a dry state for weeks.

How does it look like under the microscope?

M. tuberculosis is a curved, acid-proof , rod-shaped bacteria (mycolic acid in the cell wall) and therefore cannot be identified with a Gram stain. Instead Ziehl-Neelsen stain (acid-proof organisms stain red, while the background of debris stains blue) or a fluorochrome stain such as Auramine O are used (with Auramine O stain, organisms show a bright yellow fluorescence, non-specific debris stains pale yellow, and the background is almost black).

What about cultures?

Commonly used media are:

Middlebrook 7H9 Lowenstein-Jensen Middlebrook 7H11/7H10 Colonies need several weeks to grow. In order to distinguish the individual mycobacteria, the catalase and niacin tests are performed. Alternative tests comprise molecular biological (PCR) or mass spectrometry (Maldi-TOF) analyses.

What are the TB symptoms? Usually the immune system prevents you from becoming sick. Only 5–10 % of the infected people worldwide become ill. It is important to make a distinction between latent TB (patient is infected, the bacteria are inactive and cause no symptoms. It isn’t contagious, but can turn into active TB) and active TB (this TB makes you sick and occurs weeks or years after infection with the TB bacteria). Pulmonary TB is the most common form and affects lung function. It may, however, also spread to other organs, especially in patients with immune deficiencies (e. g., HIV).

Symptoms of active TB include:

Severe coughing, with blood Coughing for three or more weeks Fatigue Breathlessness Fever Night sweats Chills Weight loss Loss of appetite Sweating at night Chest pain, or pain with breathing or coughing What is the difference between tuberculosis and pulmonary tuberculosis? Pulmonary tuberculosis affects the lungs, but in the case of immunodeficiency then TB can also affect other parts of the body, including the kidneys, spine or brain. The symptoms depend on the organ involved. For example, back pain or blood in the urine might be indications.

How is TB cured? Usually with active TB it takes a few weeks of a special antibiotic treatment with TB medications before the patient is no longer contagious ansteckend . Besides medication, several measures are recommended:

stay home ventilate the room cover your mouth wear a face mask . . . protect your family from getting sick.

The most common medication (active tuberculosis: several drugs at once, latent tuberculosis: take only one or two types of TB drugs) include:

Isoniazid Rifampin (Rifadin, Rimactane) Ethambutol (Myambutol) Pyrazinamide In the case of drug resistance, a combination of antibiotics called fluoroquinolones and amikacin or capreomycin are given, and are used for 20–30 months. In some cases, different medications are added.

TB is a complicated and dangerous disease. Therefore, only a basic overview can be given here. Details concerning diagnosis and therapy should be looked up in reference books.

EXERCISE: 1. Mycobacterium tuberculosis is a gram-positive rod.

a) True b) False

2. If left untreated, you can die from tuberculosis.

a) True b) False

3. How to get infected with Mycobacterium tuberculosis?

a) Smear infection b) Droplet infection c) Foodborne infection d) Infection via water

You’ll find the answer on the next page

BIBLIOGRAPHY 1. Friedman L N, Dedioat M, Davies P D O: Clinical Tuberculosis, CRC Press 2020. 2. http://dict.leo.org. 3. www.dict.cc. 4. www.webster-dictionary.org.

CARMEN LOBITZ Carmen Lobitz ist freie Trainerin, Lehrerin und MTA. Sie gründete 1998 in Berlin lobitz seminare, die unter anderem Englischseminare für Health Professionals anbieten. Kontakt: mail@lobitz-seminare.de www.lobitz-seminare.de

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Pulmonary Tuberculosis

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