Tuberculosis- also known as “TB” – is a communicabledisease that most commonly affects the lungs of the body (Figure 1). This infectiousdisease is also known to damage other organs of the body like the brain, kidneys,or spine. Many people wonder what causesTuberculosis and how it can be contracted. Tuberculosis is caused by thebacteria ‘Mycobacterium tuberculosis’, which permeatesthrough the air when someone with tuberculosis in their lungs coughs, spits,laughs, sneezes,talks, etc.
(American Lung Association, 2017)asshown in figure 2. Since Tuberculosis is a contagious and slow developingpathogen, it can be contracted from spending copious amounts of time with an individualwho has the infection, like a family member or coworker; however, one can stillcontract it from a stranger (American Lung Association, 2017). Tuberculosis isone of the oldest illnesses in the world known to humans and is still one ofthe most common reasons for death today (Smith, 2003).Now, as previously mentioned, thebacterium Mycobacterium tuberculosis, the cause of TB, is a pathogenicbacterium that was first discovered in 1882 by Robert Koch (Microbiology in Pictures, 2016). This organism has anuncommon, waxy layer on the cell surface which is mainly comprised of mycolicacid. This coating is what makes the cells resistant to Gram staining, soinstead, acid-fast techniques are utilized (Microbiology In Pictures, 2016). Additionally,the bacteria requires a high concentration of oxygen to grow, and divides every15-20 hours, which is extremely slow in comparison to other bacteria, whichusually divide in minutes (Microbiology in Pictures, 2016).
It also has cellwalls that are rich in lipids and this aspect is most likely responsible forthe bacteria’s virulence and resistance (Microbiology inPictures, 2016). When in the lungs, Mycobacterium tuberculosis is taken upby alveolar macrophages, but they are unable to digest the bacterium resultingfrom the cell wall, preventing the fusion of the phagosome with a lysosome (Smith,2003). This induces the bacterium to multiply unchecked within the macrophage, thusallowing the organism to grow. The pathogen can also survive for weeks in dust,on carpet, or clothes, as well as for months in sputum (Center for DiseaseControl and Prevention, 2016). Tuberculosisis commonly found in two forms: Latent and Active TB. Persons with latent TB are infected with Mycobacterium tuberculosis, but do not have thetuberculosis disease (Mayo Clinic, 2017). Due tothe disease’s dormancy within patients, they often display no signs or symptomsof the disease (Mayo Clinic, 2017).
Therefore, they are not infectious, and cannotspread TB to others. However, active TB is when the bacterium successfullyinfects the patient, thus succumbing him/her to the disease (Mayo Clinic, 2017).This person is highly contagious and can transmit the disease to others.
Ninetypercent of adult cases of active TB are from the reactivation of a latent TBinfection (AAFP, 2017).Additionally, those who contract tuberculosisdemonstrate a variety of symptoms. Although latent TB is mostly symptomless, commonindicators of active TB include coughing with mucous or blood, chest pain,unintentional weight loss, fever, fatigue, night sweats and chills (MayoClinic, 2017). Tuberculosis can also spread via the bloodstream to affect othervital components of the body if treatment is not provided.
For instance, it canlead to spinal pain and stiffness if it reaches the spine, it can lead destructionof joints if it reaches bones, and as it infects the brain it can lead to meningitiswhich can cause headaches and mental changes (Mayo Clinic, 2017). This can alsonegatively affect the liver and kidneys as it damages their waste filtrationfunctions, and even though it is rare for TB to infect the heart, it can impairthe heart’s capabilities to pump blood effectively which is fatal (Mayo Clinic, 2017).Furthermore, those who have a weak immunesystem have a higher probability to acquire tuberculosis such as, infants andchildren whose immune system have not fully matured, people who were infected previously,persons infected with HIV, and those who have certain conditions like diabetesor chronic renal failure (American Lung Association, 2017). Nonetheless, other external elements can higher thechance of also obtaining the disease. Forinstance, tobacco and alcohol use has been found to increase the risk ofdeveloping active tuberculosis (McIntosh, 2017). In the 20th century TB was theleading cause of death in the U.S.
, and today is regarded as one of the majorcauses of disability and death worldwide (Center for Disease Control andPrevention, 2016). In 2015, 10.4 million people fell ill with TB, and 1.
8million died from the disease, as shown in Figure 3 (World Health Organization,2017). According to the World Health Organization, more than 95 percent ofthose TB deaths occurred in low and middle-income countries like Mexico, Africa,or Eastern Europe as shown in Figure 4 (World Health Organization, 2017). Infact, one third of the global population has latent TB infection, and five toten percent of those infected people will eventually develop the active TBdisease (McIntosh, 2017). Moreover, a multitude oftuberculosis cases can be cured with sufficiently administering medication andtreatment. There are many factors that contribute to the alleviation of tuberculosiswithin patients, such as, age, health, possible resistance to drugs, whether itis latent or active TB, and the location of the infection within the body (McIntosh,2017).
People with latent TB usually requirelesser doses of one or more TB prescriptions, in contrast to those with activeTB who will require higher doses, and an assortment of antibiotics and othermedications (Mayo Clinic, 2017). The standard length of time for a course of TBantibiotics is about 6 months (Center for Disease Control, 2016). Luckily,there are tests that can be taken to diagnose for TB. The skin test (purifiedprotein derivative aka PPD), is when an extract of the TB bacterium isadministered under the skin of the inner forearm via intramuscular injection andis the most common test administered for diagnosing TB (Punnoose, 2013).
Inresponse to this injection, if a person has been infected with TB, immune cellswill harden the area surrounding the injection site. The area of hardening is monitoredfor 48 to 72 hours after injection and used to determine whether a TB infectionis within one’s body. (Punnoose, 2013). Unfortunately, however, the skin testis not 100 percent accurate and has been known to incorrectly indicate thepresence of the infectious disease (McIntosh, 2017).
Nevertheless, other tests areavailable like chest x-rays, which may be done to distinguish between activeand latent TB, or blood tests, which may be done to check for cytokines thatare unique to TB infections (McIntosh, 2017). These may be used alongside theskin test to diagnose tuberculosis.