TUBERCULOSIS(TB)

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DEFINITION

Tuberculosis (TB) is an infectious disease caused by several species of mycobacterium that affects the lungs.

It is caused mainly by mycobacterium tuberculosis and rarely by mycobacterium bovis or mycobacterium africanum.  Tuberculosis affects the lungs but may spread to almost any part of the body including the meninges, kidneys and bones.

TYPES OF TUBERCULOSIS

Tuberculosis is classified as;

  1.  Pulmonary tuberculosis, which affects the lungs 
  2. Extra pulmonary tuberculosis, which affects any part of the body other than lungs.

PULMONARY TUBERCULOSIS                                                                     

This is the most common cause of tuberculosis infection.  It accounts for more than 80% of all cases of tuberculosis.

The type of pulmonary tuberculosis is as follows;

  1.   Sputum smear – positive pulmonary tuberculosis (sm+PTB), this is a patient with sputum in which mycobacterium have been found on microscopy.
  2.  Sputum smear – Negative pulmonary patient tuberculosis (MS –PTB).

This is a patient with sputum smear negative for mycobacterium on microscopy, but x-ray shows consistence with active tuberculosis which does not clear with ordinary antibiotics.

In some cases, even though sputum smear are all negative for mycobacterium on microscopy, the culture is positive for mycobacterium tuberculosis.

EXTRA PULMONARY TUBERCULOSIS

This is a type of tuberculosis that affect any other organ apart from the lungs.  Types of extra pulmonary tuberculosis are as follows;

1.      Pleural tuberculosis.

2.      Glandular tuberculosis(the glands)

3.      Tuberculosis of the spine

4.      Tuberculosis meningitis (the brain)

5.      Intestinal tuberculosis (intestines)

6.      Miliary tuberculosis (the whole body)

7.      Tuberculosis of the bone

8.      Tuberculosis of the skin

9.      Tuberculosis of the eye.

INCIDENCE

Tuberculosis can occur in persons of all ages but especially young adults in the prime of life and the aged.  Incidence is also high in the following people:

1.      People with acquired immune deficiency syndrome.

2.      Babies and young children who have weak immune systems.

3.      People who have been previously infected.

4.      People in close contact with someone who has infectious tuberculosis.

5.      People who consume alcoholic beverages and smoke heavily.

6.      Incidence is also high among health workers example nurses and doctors.

7.      Mine workers and people working in quarries

AETIOLOGY

Pulmonary tuberculosis results from exposure to mycobacterium and sometimes other status of mycobacterium from a person with active pulmonary disease who expels the organism through talking, coughing, sneezing or singing or also from droplets in the air.

Mycobacterium bovis causes bovine tuberculosis and this commonly affect cows or oxes.  Mycobacterium africancum is at variant of mycobacterium tuberculosis both of which affect human beings. 

PATHOPHYSIOLOGY

When a person inhales aerosol particles contaminated by the germs of tuberculosis, they are carried into the lungs and into the delicate epithelia surface of the alveoles, they cause swelling and local capillary dilation.

Although some organisms will be engulfed by alveolar macrophages, all will not be destroyed and will continue to multiply.  The invasion of the lung tissue by the bacteria give rise to an inflammatory reaction in which the affected alveoli are filled with fluid, macrophages and bacteria.  The degeneration of the lung tissue gives rise to or forms a cheesy mass which is referred to as cessation. The resultant lung damage eventually leads to fibrosis which will be visible on x-ray.

The primary lesion in the lungs is often asymptomatic and confined to one area, and these tiny areas where the healing occurs by scar formation and even by the deposit of calcium are called granulomas. A primary infection may heal with the host acquiring immunity in the process, in some cases, the primary lesion progresses to produce extensive disease locally or the infection disseminate to produce metastic or miliary lesions. Thus some of the bacteria will escape and may enter the blood stream to infect other organs of the body.  This form of tuberculosis is called extra pulmonary or miliary tuberculosis.

Militry tuberculosis usually occurs in the lymph nodes, meninges, joints, peritonium,

 genito- urinary tract and bowel.            

Tuberculosis present a chronic cough with mucopurulent sputum as the disease becomes advanced. Dominant bacillinary also become reactive when any of the predisposing factors or combination of them prevail.

SIGNS AND SYMPTONS OF PULMONARY TUBERCLUSIS

·         Clinical Manifestation of pulmonary tuberculosis include;

1.      A bad cough that lasts longer than two weeks

2.      Pain in the chest

3.      Coughing up blood or sputum ( phlegm from deep inside the lungs)

4.      Shortness of breath 

·         General signs and symptoms of tuberculosis

1.      Dry persistent cough

2.      Weakness and fatigue

3.      Profuse night sweats

4.      Mucopurulent or blood stained sputum

5.      Haemoptysis

6.      Dyspnoea with chest pains

7.      Weight loss

8.      Low grade fever with intermittent temperature

9.      Anorexia

10.  On auscultation, crepitant cranks, bronchial breath sounds and wheezing may be heard.

11.  Pallor and anaemia.

12.  There is low grade fever.

COMPLICATIONS

 Pleural effusion

Hoarseness of voice

3.     Pulmonary fibrosis
4.     Tuberculosis bronchopneumonia
5.      Airway obstruction
6.      Tuberculosis empyema ( pus in pleural cavity)
7.      Fungus infection in the cavity
8.      Enteritis
9.      Death
10.  Collapse of the lungs
11.  Ischiorectal abscess

DIAGNOSTIC INVESTIGATIONS

Specific Diagnostic Test

i)                   Sputum smear test – Gastric aspiration, laryngeal swab for ziehl- Nelson stains and fluorescent microscopic examination for tuberculosis and also for culture and sensitivity to antibiotics. Positive sputum indicates open tuberculosis

ii)                 Radiology of chest and lungs show the shadows of inflammation and there may be calcification especially in the upper lobes of the lungs.

iii)               Positive tuberculin skin test

iv)               sputum smear for AFB (Acid fast Bacilli)

v)                  Purified protein derivatives (PPD)

vi)               Screen test or multiple puncture test

vii)             Chest X-ray

MEDICAL TREATMENT

·         DRUG TREATMENT

The national tuberculosis programme (NTP) uses three types of standardised treatment regimen. All regimen start with an initial intensive phase followed by a continuation phase.

(A)    THE SHORT COURSE

This course is for;

1.      New smear positive pulmonary tuberculosis patient.

2.      Patients whose sputum smears are negative but who are seriously ill.

The course consists of two months intensive phase followed by six months continuation phase. The dosage given usually depends on the age and weight of the patient.

The drugs used for the intensive phase are:

i)                   Streptomycin (intramuscularly)

Dosage: Adult – 1g daily for two months (reduces dosage for elderly and emaciated)

  Children – 20mg1kg body weight daily for 2months.

ii)                 Rifiriah (intramuscularly or orally)

Dosage: Adult – 1g daily for two months.

  Children: 10mg1kg body weight for two months.

iii)               Pyrazinamide (orally)

Dosage: Adult – 2g daily for two months

              Children – 35mg1kg body weight for two months.

The drug for the continuation phase is;

·         Thiacetazone (orally)

Adult dosage: 450mg daily for six months.

Children

·         Rifiriah ( orally or intramuscularly)

Dosage: 10mg1kg body weight daily for six months

If there is a high suspicion of HIV infection in a patient, the thiacetazone may be change to isoniazid plus ethambutol

·         Ethambutol (orally)

Dosage 400mg daily for six months

·         Isoniazid ( orally or intramuscularly)

Dosage 300mg daily for six months.

(B)  STANDARD COURSE

This consists of 12months duration for smear negative pulmonary tuberculosis and extra pulmonary tuberculosis cases.

It comprises of two months intensive phase treatment with streptomycin, isoniazid and thiacetazone.

It is followed by 10months continuation phase with isoniazid and thiacetazone.

Administration of thiacetazone can cause Stevens Johnson syndrome in patients with HIV hence are not put on standard course.

(C)  RETREATMENT COURSE

This is for relapse and treatment failure cases.

It comprises of initial intensive phase of five drugs

·         Rifampicin

·         Isoniazid

·         Pyrazinamide

·         Ethambutol.

Daily for three months supplemented with streptomycin for two months. This phase is strictly supervised and if possible the patient is admitted.


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