Bệnh Lao (Mycobacterium tuberculosis)

Bệnh Lao (Mycobacterium tuberculosis)


Tuberculosis or TB is one of the oldest
and most common infectious diseases About one third of the world population
is believed to be infected with TB Fortunately, only about 5% of
these infections progress to active disease The other 95% of
infected people are set to have a dormant or latent infection They do not
develop any symptoms and do not transmit the disease Tuberculosis is caused by a rod-shaped
bacterium or a bacillus called mycobacterium tuberculosis In infection is
initiated following inhalation of mycobacteria present and aerosol
droplets discharged into the atmosphere by a person with an active infection The transmission process is very
efficient as these droplets can persist in the atmosphere for several hours and
infectious dose is very low, less than 10 bacilli are needed to start the
infection Once in the lung the bacteria meet with
the body’s first line defense, the macrophages The bacteria are ingested by the
macrophages but managed to survive inside Internalization of the bacilli triggers
an inflammatory response that brings other defensive cells to the area Together, the cells form a massive tissue called a granuloma characteristic of the
disease And its early stage, the granuloma has a core of infected
macrophages and close by other cells of the immune system As cellular immunity develops,
macrophages loaded with bacteria are killed resulting in the formation of the
caseous center of the granuloma the bacteria become dormant but may remain
alive for decades This enclosed infection is referred to
as latent tuberculosis and may persist throughout a person’s life without
causing any symptoms The strength of the body’s immune
response determines whether an infection is arrested sheer or progresses to the
next stage In healthy people the infection may be stopped permanently
at this point the granulomas subsequently heal, leaving small
calcified lesion On the other hand, if the immune system is compromised by
immunosuppressive drugs, HIV infections, malnutrition, aging or other factors, the
bacteria can be reactivated, replicate, escape from the granuloma and spread to
other parts of the lungs, causing active pulmonary tuberculosis This reactivation
may occur months or even years after the initial infection In some cases the bacteria may also
spread to other organs of the body via the lymphatic system or the bloodstream This widespread form of TB disease
called disseminated TB or miliary TB, occurs most commonly in the very young,
the very old, and those with HIV infections Tuberculosis is generally treatable with
antibiotics Several antibiotics are usually
prescribed for many months due to the slow growth rate of the bacteria It’s very important that the patient’s
complete the course of the treatment to prevent development of drug-resistant
bacteria and reoccurrence of the disease

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