Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis. It most commonly affects the lungs but can affect other parts of the body. The disease spreads through airborne droplets when infected people cough, sneeze or speak. Diagnosis involves medical history, physical exam, tuberculin skin test, chest x-ray and microbiological tests. Treatment requires a combination of antibiotics taken for at least 6-12 months to prevent drug resistance from developing. Prevention strategies include identifying infected individuals and their contacts, testing high-risk groups, and immunizing infants with the BCG vaccine.
2. DISCRIPTION
ο Tuberculosis is a chronic infectious disease caused by
tubercle bacilli.
ο TB most commonly affects the lungs (pulmonary
TB) but can also affect the central nervous system
(meningitis), lymphatic system, genitourinary
system, joints and bones.
ο The causative agent of TB was identified by Robert
Koch in late 19th century.
ο TB is one of the top four infectious killer diseases in
the world. The World Health Organization declared
TB a global health emergency in 1993.
3. CAUSATIVE ORGANISM
ο Tuberculosis (commonly abbreviated as TB) is
an infection caused by the bacterium
Mycobacterium tuberculosis.
ο It is a slow-growing aerobic small rod like
bacilli and divides every 16 to 20 hours.
ο In the most common staining technique, is
Ziehl-Neelsen stain mathod or acid fast
staining technique.
4. Jha, A. K. et al. N Engl J Med 2004;350:2399-2404
5. MODE OF SPREAD
ο It is spread by droplet infection.
ο TB is spread by aerosol droplets expelled by people
with active TB disease (not latent TB infection) of
the lungs when they cough, sneeze, speak, or spit.
ο Each aerosol droplet is 5 ΞΌm in diameter which
contains 1 to 3 TB bacilli.
6. INCUBATION PERIOD
ο Incubation period varies from few months to
a few years depending upon the host- parasite
contact and severity of infection.
7. SIGNS AND SYMPTEMS
ο Cough for more than
three weeks
ο Coughing up blood
ο Unexplained weight
loss
ο Night sweats
ο Fever
ο Feeling tired
8.
9. DIAGNOSIS
The medical evaluation for TB includes
ο complete medical history,
ο physical examination,
ο the Mantoux or tuberculin skin test,
ο serological test,
ο chest X-ray, microbiologic smears,
ο isolation of acid-fast bacterium,
ο cultures,
ο commercially available DNA probes and the
BACTEC NAP test.
10. Mantoux or Tuberculin test
ο Sufficient quantity of tuberculin solution (5 units) is
administered intra-dermally in to the skin of the left
forearm.
ο The site of inj. is examined after 72 hrs.
ο If there is swelling (6-10 mm ) at the site of injection
is considered as positive.
ο Reaction less then 6 mm considered as negative.
11. TREATMENT
ο For all practical purposes, only patients with tuberculosis of
the lungs can spread TB to other people. People with LTBI
and are not capable of passing the infection to other people.
ο The distinction is important because treatment options are
different for the two groups.
ο Both chemotherapy and chemoprophylaxis are carried out by
administering isoniazid, plus rifampicin, ethambutol, and
pyrazinamide.
ο These drugs are administered simultaneously for 12-24
months as a way of decreasing the possibility that the patient
develops drug resistance.
12. PREVENTIONAND CONTROL
ο Prevention and control of TB requires rapid specific
therapy to interrupt infectious spread. The efforts
include these priority strategies:
ο Identifying and treating all people who have TB.
ο Finding and evaluating persons who have been in
contact with TB patients to determine whether they
have TB infection or disease, and treating them
appropriately.
ο Testing high-risk groups for TB infection to identify
candidates for treatment of latent infection and to
ensure the completion of treatment.
13. VACCINES
ο Many countries have immunization programs
against tuberculosis, especially for infants.
ο The vaccine is a non-virulent variant of
Mycobacteriun bovis called BCG (bacillus of
Calmette and Guerin) that stimulates at least partial
immunity against tuberculosis by inducing the
proliferation of sensitized lymphocytes.
