Tuberculosis is a contagious disease caused by a bacterium called Mycobacterium tuberculosis

Running head: TUBERCULOSIS
Clinical science: Tuberculosis
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Table of Contents
Introduction................................................................................................................................2
Aetiology and pathogenesis.......................................................................................................2
Causes and risk factors...........................................................................................................2
Pathophysiology.....................................................................................................................3
Clinical implications..............................................................................................................4
Clinical manifestations...............................................................................................................4
Diagnostic process.....................................................................................................................6
Treatment...................................................................................................................................7
Pharmacological management...............................................................................................7
Non-pharmacological management.......................................................................................8
Health promotion...................................................................................................................8
Conclusion..................................................................................................................................8
References................................................................................................................................10

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Introduction
Tuberculosis is a contagious disease caused by a bacterium called Mycobacterium
tuberculosis, damaging the lungs and thereby causing serious illness and death. This disease
is not contagious and can be transmitted only from an active patient of TB by inhaling their
coughs, sneezes, respiration around the TB-active patient (Healthdirect.gov.au, 2020). It is
one of the leading health concerns over the globe. The World Health Organisation reported a
count of nearly 10 million people infected with TB and a mortality count of 1.5 million
people around the world in 2018 (Who.int, 2020). In Australia, the National Disease
Surveillance System (2014) reported 1,339 cases of TB, which represents a rate of 5.7 per
100,000 people. Moreover, the rate of multi-drug resistant TB (MDR-TB) was about 1-2%.
Majority of the notifications of TB recorded is in the Aboriginal and Torres Strait Islanders
recording about six times higher cases than the non-Indigenous communities in Australia
(Www1.health.gov.au, 2020). The objectives of this paper is to discuss the different clinical
aspects of tuberculosis (TB) including the aetiology and pathogenesis of TB, its clinical
manifestations, the diagnostic process and various methods of treatment.
Aetiology and pathogenesis
Causes and risk factors
The causal organism of TB is Mycobacterium tuberculosis, which is a bacteria infecting the
lungs of humans. The route of its transmission is similar to that of the flu or cold, however, it
is less contagious than these diseases. It is spread by inhaling the expelled droplets from the
coughs, sneezes or speech or singing of an infected individual with an active TB. Active TB
refers to the presence of the causal organism inside the person’s body but has not displayed
any symptom, which might take years, months or even some weeks to manifest (Lin et al.,

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2014). The risk development of TB consists of both endogenous and exogenous factors.
Some of the endogenous factors include malnutrition, human immunodeficiency virus (HIV),
age, alcohol consumption, immunosuppressants, diabetes and tobacco smoke. Similarly,
exogenous factors also contribute to the progression of TB. The chief exogenous risk factors
regulating the development of including the load of bacillus in sputum and the proximity with
the infected person. These risk factors play a significant role in both the community and the
individual level (Narasimhan et al., 2013).
Figure 2: Risk factors for TB (Narasimhan et al., 2013)
Pathophysiology
The pathophysiology of tuberculosis consists of three stages, namely the primary infection,
latent infection and the active infection. The bacillus bacterium causing TB, M. tuberculosis
begins with a primary infection and is rarely associated with an acute infection. Almost 95%
of the primary infections are asymptomatic, which subsequently leads to the dormant or latent
phase. The transmission of the infection is not contagious in the primary or the latent phases.
The development of infection requires the inhalation of microscopic particles to be able to
traverse through the defence system of the upper respiratory tract and accumulate in the

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lungs, primarily in the sub-pleural airspaces of the lower or middle lobes. The larger droplets
do not readily cause the infection as they tend to get lodged in the proximal airways. The
bacilli have to be ingested by the alveolar macrophages to initiate infections. The infection
progresses if the macrophages of the host are unable to kill the bacteria. The bacteria not
controlled by the macrophages results in their multiplication and finally killing the
macrophages of the host.
During the initial weeks of the infection, the infected macrophages enter the bloodstream by
migrating to the mediastinal, hilar or other regional lymph nodes. Through the bloodstream,
the bacteria can spreads hematogenously to different organs, specifically the apical-posterior
region of the lungs, meninges, kidneys and epiphyses of long bones. This spread to the
different organs of the body and its effect depends on the immune system of the infected
person.
Latent infection is generally observed after the primary infection. In maximum cases, the
immune system of the host suppresses the replication of the bacillus, even before the
development of the symptoms. The phase of the infection is entirely determined by the
balance between the microbial virulence and the resistance of the host. Depending on the age
and other significant factors, healthy individuals that have been infected with TB are at risk
of developing active TB. In about 80% of these cases, the reactivation of TB is observed
within the first two years but can be detected after some decades as well. The reactivation can
occur in any organ, but the lungs are the most susceptible due to the high oxygen tension in
the region. Extrapulmonary TB may also manifest at sites in the absence of any involvement
of the lungs. The most widespread pulmonary presentation is TB lymphadenopathy.
However, the most fearful presentation of this TB is meningitis, attributing to the highest
mortalities.

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Figure 1: Pathophysiology of pulmonary tuberculosis (Retrieved from
http://www.southsudanmedicaljournal.com/archive/february-2013/tuberculosis-2-
pathophysiology-and-microbiology-of-pulmonary-tuberculosis.html)
Clinical implications
As the causal organism for TB is transmitted through the expelled droplets from the coughs,
sneezes or while the infected person is speaking or singing, it is a contagious disease. This
contagious property of TB poses a serious public health concern as I can spread rapidly.
Moreover, in many cases, the infection can be transmitted even before the development of the
symptoms. Thus, the clinical implications of TB make it a severe public health issue.
Clinical manifestations
The clinical manifestations of TB include primary TB, lower lung field TB, reactivation TB,
laryngeal TB, endobronchial TB, and tuberculoma. The clinical manifestations of an active
tuberculosis include a persistent, non-remitting cough extending for over three weeks, night
sweats, fever, chills, loss of appetite and weight loss. The clinical symptoms may also be
observed in specific organs other than the lungs and affect the functioning of the particular

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organ. Other significant clinical signs of active TB include coughing up sputum or blood and
extreme fatigue. . Latent TB demonstrates no clinical presentation as it is asymptomatic.
The infected individuals developing progressive primary TB are accompanied with
pneumonia and increase in infiltrates around the hilum or near the initial seeding site. They
may also present hilar lymphadenopathy or demonstrate effects at distant locations, some of
which are cervical lymphadenopathy, pericarditis, meningitis or military dissemination. This
progression is more frequent in individuals with weak immune systems, which include
chronic kidney concerns, HIV infections, uncontrolled diabetes mellitus and on
immunosuppressive medications, and older adults as well as young children.
The clinical manifestations of TB might take varying time from weeks to months. The
predicted triad of nightsweats, weightloss and fever are presented in approximately 55-75%
infected individuals. The persistent cough is the most commonly reported manifestation and
is observed in 95% of the patients. Of the total reported cases of active TB, about 20% are
exclusively pulmonary cases of TB. Clinical manifestations of parenchymal TB include
dyspnea and non-productive cough accompanied with mucopurulent or blood-stained sputum.
In pleural TB, the clinical presentation includes localized chest pain with fever and cough.
Clinical symptoms of military TB are typically constitutional, observed as malaise,
weightloss, fever, sweats and anorexia. Neurological manifestations such as headache, cranial
nerve palsies and decreased consciousness may also be observed if the brain is also infected.
The most widespread manifestation of central nervous system (CNS) TB includes
tuberculosis meningitis (TBM) and CNS tuberculoma.
Diagnostic process
Early diagnosis of TB in the active form is a priority to control the disease, in the context of
benefit for both the individual affected with it and for the public health safety to stop the

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progression and spread of the disease. however, rapid diagnosis of TB is challenging in
clinical practice. Some of the methods of diagnosis of TB include Radiological study such as
chest X-rays, smear microscopy and molecular methods. The radiological approach of X-ray
of the chest is the fundamental diagnostic method for the evaluation of TB. This approach
provides vital information for managing and following-up of the infected patients and serves
as an important tool to monitor complications. This technique of chest X-ray is effective but
cannot be specifically used for pulmonary TB as it may show normal results even in the
presence of the disease. Thus, the results of this test are inconclusive and is not an
independently reliable method of diagnosis. Consequently, chest X-rays are followed with a
test of the sputum for more confirmatory results. The manifestation of the post-primary TB is
observed as a cavitary opacity in the superior regions of the lower lobes and the posterior and
apical regions of the upper lobes. This cavitation is observed in more than 50% of the patients
and is a hallmark of the disease. Despite the widespread use of chest X-ray as a tool for
diagnosis of TB, chest computed tomography (CT) is required in many cases for the detection
of the fine lesions which are frequently overlooked on the X-ray of the chest. These lesions
help in the evaluation of complications or equivocal lesions (Santosh & Antani, 2017).
Sputum serves as the most critical sample for diagnosing pulmonary TB. Sputum is used for
laboratory testing by the technique called Direct sputum smear microscopy and is the most
widespread method of diagnosis available in major health centers and primary health care
laboratories. Ziehl-Neelsen-stained smears are prepared from the sputum sample, which is
then observed under the conventional light microscope to diagnose TB in seting wherere
resources are limited. In contrast, the conventional fluorescence microscopy is a more reliable
technique as its sensitivity (10%) is higher than the Ziehl-Neelsen and cosumes less time.
However, it is an expensive method of diagnosis (Ryu, 2015). In response, Light-emitting
diodes (LED) microscopes have been developed to be associated with the fluorescence to

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reduce their costs and has also been recommened by the WHO to be used as an alternative to
the conventional Ziehl-Neelsen light microscopy (World Health Organization, 2020).
Treatment
Pharmacological management
The first-line pharmacological treatment for TB includes antituberculous drugs such as
isoniazid, pyrazinamide, rifampicin and ethambutol. Isoniazid and rifampicin act as
bactericidal and specifically useful against metabolically active microorganisms to reduce
their rapis growth and replication. Rifampicin is relatively more active than isoniazid and also
effective against bursts of metabolic activities of bacilli. Pyrazinamide also demonstrates
bactericidal properties and is particularly effective against mycobacteria in acidic
environments and is valuable against relapse of TB. Ethambutol is a bacteriostatic drug and is
primarily used as a supplement to reduce resistance. The typical dosage includes the
administration of the isoniazid with rifampicin for six months, accompanied with ethambutol
and pyrazinamide in the initial two months to ensure the total destruction of both dormant
and active forms of the bacteria (Alsultan & Peloquin, 2014). These combinations of drugs
are associated with a variety of side-effects such as itching or redness of the skin in sunlight,
sleep disorders, orange-coloured saliva and urine and mild ache in the upper abdomen and
joints (Seung, Keshavjee & Rich, 2015).
Drug Classes Anti-TB Drugs Comments
First-line drugs Isoniazid (INH) They constitute the core
elements of initial treatment
regimen.
Rifampin (RIF)
Pyrazinamide (PZA)
Ethambutol (EMB)

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Rifabutin* (RBT) It can be used as an
alternative to RIF in treating
TB
Rifapentine (RPT) It can be used once in a week
with INH in HIV-negative
patients with drug-
susceptible, non-cavitary
pulmonary TB with negative
sputum smears on early
completion of treatment
Second-line drugs Streptomycin (SM) It was initially used as a first-
line drug but discontinued
due to resistance to SM in
many cases.
Cycloserine These drugs are used only in
cases of drug resistance or
intolerance
Capreomycin
Table 1: Treatment interventions for TB (Retrived from
https://www.cdc.gov/tb/education/corecurr/pdf/chapter6.pdf)
Non-pharmacological management
Along with the conventional pharmacological management of TB, some approaches
involving non-pharmacological approaches are also used to increase the efficacy of the
treatment. Some of these approaches include increasing the oxygen supply of air for the
patient by improving room ventilation and oxygen supplements for people exhibiting adverse
conditions. Another such approach includes physiotherapy, which serves as a tool to clear

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bronchial secretions. Some important aspects of physiotherapy include muscle training and
exercises for pulmonary rehabilitation (Ong, Elkington & Friedland, 2014).
Health promotion
Australia achieved significant milestones in preventing the spread of TB through its previous
plan of Strategic Plan for the Control of TB in Australia, 2011-2015. Various policies and
guidelines were introduced during this plan as an effort of the government to prevent the
spread of the disease and promotion of health. The recent Strategic Plan for Control of
Tuberculosis in Australia, 2016–2020: The plan ‘Towards Disease Elimination’ is an
updated version of the previous plan with an aim to eliminate TB. It promotes health by
continuing its strategies of maintain an experience workforce for TB, among other strategies.
However, this goal of eliminating TB from Australia requires an expansion of the current
programs to other supported programs for extending the health portfolios to other related
agencies (Www1.health.gov.au, 2020).
Conclusion
In conclusion, the increasing prevalence of tuberculosis is becoming a global health concern.
The causal organism of TB is a bacterium called Mycobacterium tuberculosis. The rapid
spread of TB can be attributed to its air-borne route of transmission through the droplets
expelled from an infected person, which is in turn inhaled by a healthy individual. However,
the spread of TB is not as rapid and contagious as the cold or flu. The clinical manifestations
of TB can be observed as a persistent cough for over three weeks, fever, chills, night sweats
and loss of weight. Some of the extrapulmonary manifestations may also present blood-
stained or mucopurulent sputum. These manifestations are confirmatory with the help of
various diagnostic methods such as chest X-ray, sputum smear microscopy and the more
recent molecular methods of diagnosis. The treatment for TB includes a combination of

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pharmacological, non-pharmacological and health promotion programs with an aim to reduce
the prevalence and ultimately eliminate TB from Australia.

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