Biomedical Engineering Reference
In-Depth Information
of drug resistance WHO (World's Health Organization) implemented
DOTS (Directly Observed Treatment, short course), program which was
not successful in solving the patients non-compliance [32]. As Figure 14.3
below discloses, most patients fail to adhere to multidrug therapy for lon-
ger periods of time.
Tubercle bacilli are slender, acid fast, non-motile gram-positive bacilli.
h ese bacteria remain viable in the air for longer period of time as a result
of which they get inhaled by the lungs and engulfed by alveolar macro-
phages (white blood cells) where they start replicating within 2-3 weeks
[33]. If these bacteria is not completely destroyed, they remain dormant
for several days and may reactivate years later. h e cell wall has high lipid
content which allows the bacteria to survive within macrophages. Because
of the impermeable nature of the cell wall, drugs are only partially ef ective
and organisms develop resistance [4]. h e bacilli can spread from the site
of infection in the lung through the lymphatic or blood to the other parts
of the body. Extra pulmonary TB of the pleura, bone, genitourinary sys-
tem, skin or peritoneum, meninges occurs in approximately 15% of the TB
patients [8]. Risk of development of active disease varies according to time
according to infection, age, host immunity, however life time risk of death
for a newly infected child has been estimated 10% [34-36]. Available TB
treatment involves daily administration of four oral antibiotics for a period
Mycobacterium tuberculosis
from air get engulfed by
alveolar macrophages
Free
Mycobacterium tuberculosis
released from granuloma center
Infected macrophages entered
into blood vessel
Life Cycle of
Mycobacterium tuberculosis
Formation of caseum
(cells are in dormant phase)
Differentiation of infected
macrophages into
foamy macrophages
Formation of fibrous cuff made up of
extracellular matrix around
foamy macrophages
Figure 14.3
Lifecycle of
Mycobacterium tuberculosis.
