Tuberculosis

Tuberculosis, otherwise known as TB or Consumption (if you’re feeling old fashioned) is a lower respiratory tract infection caused by bacterium Mycobacterium Tuberculosis. Though cases have been steadily declining since the 1900’s, there were still over 9,000 cases in the United States in 2014, almost 500 deaths in the same year. It is still one of the most common causes of death internationally right under diarrheal diseases and dementia. Due to the highly contagious nature of the disease, and its long latent period it is important for health care professionals to be proficient in recognizing TB.

Around one third of the world is infected with latent tuberculosis. This may seem alarming but latent tuberculosis cannot be transmitted and one does not experience symptoms in this stage. Only about 10% of people with healthy immune systems infected with LTBI will fall ill with TB.

Gram positive bacterium that is contracted through inhalation or aerosols. Mycolic acid creates a waxy layer on the outside of the bacterium that greatly increases virulence of the bacteria.

Since transmission of TB occurs through inhalation, the initial contact of the bacteria is in the mucus membranes of the nasal passages, upper respiratory tract or lower respiratory tract. They will typically migrate towards the alveoli where the local macrophages will ingest the foreign pathogens.

In this process the body will destroy most of the bacilli, unfortunately a small percent will survive inside the macrophages and replicate. These macrophages may eventually be killed, but the bacilli inside can propagate within the body through the lymphatic and circulatory systems. They will typically settle in distinct areas including: the brain, long bones, the spine, meninges, the larynx, lymph nodes, the lungs or the kidneys where they will be consumed by macrophages. It is important to note that hematogenous dissemination is less common in patients that have received tuberculosis vaccinations.

The presence of the infection will then attract other immune cells such as fibroblasts that will create a granuloma around the infected macrophages. These granulomas called tubercles can developped necrotic centers but the bacilli may still survive within them for years. The process of keeping these granulomas sealed and the infection latent, is an active one. Sometimes the immune system fails causing Secondary TB or active TB.

This usually occurs due to suppression of the immune system though, as I mentioned earlier, 10% of otherwise healthy individuals will still develop an active infection. The active infection may then escape attack the body. The rupture of these granulomas themselves can cause spontaneous pneumothoraces as well.

Patients at risk include anyone with a suppressed immune system, notably HIV possitive patients. Tuberculosis cases actually increased during the HIV crisis in the late 80’s and still accounts for 35% of HIV deaths globally. However, patients with Diabetes mellitus, chronic alcoholics and all other patients with lowered immune responses are also at significant risk.

Patients living in high risk areas such as hospitals, nursing homes and crowded living quarters are at higher risk due to their frequent contact with the sick and difficulty sanitizing their environment such as people living in homelessness or overcrowded living conditions.

The United States and Canada have generally low instances of TB, however certain countries especially countries with higher instances of HIV see many more cases annually. Countries such as India, South Africa and China are still struggling with high infection rates and people traveling, immigrating or living in these countries are at higher risk.

• Anorexia
• Fatigue
• Weight loss
• Cough (may produce yellow, green sputum or blood)
• Chest pain
• Hemoptysis
• Low grade fever
• Night sweats
• Spontaneous pneumothorax
• Pleural effusion
• Dyspnea

*Note that symptoms listed may appear alone and develop slowly especially non-respiratory symptoms, likely to occur at the beginning of the illness, such as weight loss or fatigue.

The drug regiment for tuberculosis is a 6-month regiment, which is difficult for people to commit to. Patients undergoing such treatment are often followed closely by medical professionals or even properly trained volunteers to ensure medication is taken as prescribed.

This regiment consists of isoniazid, rifampin, pyrazinamide, and ethambutol in the first 2 months. Then just isoniazid and rifampin for an additional 4 months. It can be extended and pyrazinamide is occasionally removed for patients with hepatic damage, gout or pregnancy.

Tuberculosis is typically diagnosed using x-ray, sputum culture and skin tests.

Chest x-ray will show the tubercles. They usually appear in a ring formation.

When doing sputum cultures remember that mycobacterium tuberculosis is a gram-positive bacterium but because of the presence of mycolic acid it does not stain consistently. The most accurate test for tuberculosis is the Xpert MTB/RIF® a nucleic acid amplification test (NAAT) that also indicates resistance to rifampicin (RIF). Though this test is done in combination with an acid-fast bacilli test.

The skin test administered is called the mantoux tuberculin skin test or a purified protein derivative (PPD). The test involves injecting PPD intradermally and waiting 48 to 72 hours for the body to react to the injection. Depending on the patients’ medical history different diameters of induration constitute as a positive result.

A 5mm induration would be positive result in an immunosuppressed patient (HIV+, organ transplant recipient, etc.), a patient with a previous x-ray showing tubercles or any patient with close contact to a someone diagnosed with tuberculosis.

A 10mm induration would be positive result in anyone with other kind of risk factor such as recent travel/immigration from an at-risk country, working in health care or near at risk persons, patients with weakened immune systems, injection drug users and young children.

A 15mm induration would be a positive result in any healthy individual.

TB Risk Factors. (2016, March 18). Retrieved September 05, 2017, from https://www.cdc.gov/tb/topic/basics/risk.htm

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World Health Organisation. (2017, March). Tuberculosis (TB). Retrieved September 06, 2017, from http://www.who.int/mediacentre/factsheets/fs104/en/

 The top 10 causes of death. (n.d.). Retrieved September 09, 2017, from http://www.who.int/mediacentre/factsheets/fs310/en/

Sterling, T. R., MD. (n.d.). Treatment of drug-susceptible pulmonary tuberculosis in HIV-uninfected adults. Retrieved September 09, 2017, from https://www.uptodate.com/contents/treatment-of-drug-susceptible-pulmonary-tuberculosis-in-hiv-uninfected-adults?source=search_result&search=tuberculosis treatment&selectedTitle=1~150

Sanders, M. J. (n.d.). Mosby's Paramedic Textbook (Fourth ed.). Louis, MI: Mosby.