Q- What Is Tuberculosis (TB)?
Ans- Tuberculosis (TB)
Tuberculosis (TB) is an infectious
disease caused by bacteria Mycobacterium tuberculosis. TB most commonly affects
the lungs but also can involve almost any organ of the body. Today,
tuberculosis usually can be treated successfully. There is also a group of
organisms referred to as atypical tuberculosis which do not cause disease and
are referred to as "colonizers," because they simply live alongside
other bacteria in our bodies without causing damage. At times, these bacteria
can cause an infection that sometimes appears as typical tuberculosis.
How does a person get tb?
A person can become infected with
tuberculosis bacteria when he or she inhales minute particles of infected
sputum from the air. The bacteria get into the air when someone who has a
tuberculosis lung infection coughs, sneezes, shouts, or spits (which is common
in some cultures). People who are nearby can then possibly breathe the bacteria
into their lungs. You don't get TB by just touching the clothes or shaking the
hands of someone who is infected. Tuberculosis is spread (transmitted)
primarily from person to person by breathing infected air during close contact.
There is a form of tuberculosis, however, that is transmitted by drinking
unpasteurized milk caused by Mycobacterium bovis. Previously, this bacterium
was a major cause of TB in children, but it rarely causes TB now since most
milk is pasteurized (a heating process that kills the bacteria).
What happens to the body when a person
gets tb?
When the inhaled tuberculosis bacteria
enter the lungs, they can multiply and cause a local lung infection
(pneumonia). The local lymph nodes associated with the lungs may also become
involved with the infection and usually become enlarged. In addition, TB can
spread to other parts of the body. The body's immune (defense) system, however,
can fight off the infection and stop the bacteria from spreading. The immune
system does so ultimately by forming scar tissue (fibrosis) around the TB
bacteria and isolating it from the rest of the body and the infection is
contained in an inactive state. Such an individual typically has no symptoms
and cannot spread TB to other people. The scar tissue and lymph nodes may
eventually harden, like stone, due to the process of calcification of the scars
(deposition of calcium from the bloodstream in the scar tissue). Sometimes,
however, the body's immune system becomes weakened and the TB bacteria break
through the scar tissue. For example, the immune system can be weakened by old
age, the development of another infection or a cancer, or certain medications
such as cortisone, anti-cancer drugs, or certain medications used to treat
arthritis or inflammatory bowel disease. The breakthrough of bacteria can
result in a recurrence of the pneumonia and a spread of TB to other locations
in the body. The kidneys, bone, and lining of the brain and spinal cord
(meninges) are the most common sites affected by the spread of TB beyond the
lungs.
Who gets Tb?
Anyone can get TB, but certain people
are at higher risk, including:
·
People who live with individuals who
have an active TB infection,
·
Poor or homeless people,
·
Foreign-born persons from countries
that have a high prevalence of TB
·
Nursing home residents and prison
inmates,
·
Alcoholics and intravenous drug
abusers,
·
People with diabetes, certain cancers,
and HIV infection (the AIDS virus)
·
Healthcare workers.
·
There is no strong evidence for a
genetically determined (inherited) susceptibility for TB.
How does a doctor diagnose
tuberculosis?
TB can be diagnosed in several
different ways, including chest X-rays, analysis of sputum, and skin tests. The
chest x-rays can reveal evidence of active tuberculosis pneumonia or may show
scarring (fibrosis) or hardening (calcification) in the lungs. Examination of
the sputum on a slide (smear) under the microscope can show the presence of the
tuberculosis bacteria. A sample of the sputum can also be grown (cultured) in
special incubators so that the tuberculosis bacteria can subsequently be
identified. The organism can take up to six weeks to grow in culture in the
microbiology lab. Several types of skin tests are used to screen for TB. These
socalled tuberculin skin tests include the Mantoux test and the PPD (purified protein
derivative) test. In each of these tests, a small amount of purified extract
from dead tuberculosis bacteria is injected under the skin. If a person is not
infected with TB, then no reaction will occur at the site of the injection (a
negative skin test). If a person is infected with tuberculosis, however, a
raised and reddened area will occur around the site of the test injection. This
reaction, a positive skin test, occurs about 48 to 72 hours after the
injection. If the infection with tuberculosis has occurred recently, however,
the skin test can be falsely negative. The reason for a false negative test
with a recent infection is that it usually takes 2 to 10 weeks after the time
of infection with tuberculosis before the skin test becomes positive. The skin
test can also be falsely negative if a person's immune system is weakened or
deficient due to another illness such as AIDS or cancer, or while taking
medications that can suppress the immune response, such as cortisone or
anti-cancer drugs. The special test detects the genetic material of the
bacteria, called the PCR (polymerase chain reaction). This test is extremely
sensitive (it detects minute amounts of the bacteria) and specific (it detects
only the TB bacteria). One can usually get results from the PCR test within a
few days.
How is tuberculosis treated?
1. A person with a positive skin test, a normal chest x-ray,
and no symptoms most likely has only a few TB germs in an inactive state and is
not contagious. Nevertheless, treatment may be recommended for this person to
prevent the TB from turning into an active infection.
Is HIV/aids associated with
tuberculosis?
Because of HIV, a tremendous increase
in the frequency (incidence) of TB occurred in the '80s and throughout the
'90s. This increase in TB happened because suppression of the body's immune
(defense) system by HIV allowed TB to occur as a so-called opportunistic
infection. Hopefully, control of HIV in the future will check this resurgence
of tuberculosis.
Can tuberculosis be prevented?
Yes. The most important step is to find, isolate and
treat all disease carriers until they are no longer an infective risk to
others. Make sure that you eat well and enjoy plenty of sunlight and exercise
It is always advisable not to get too close to people who are coughing;
equally, people with a cough should be aware of those around them and try not
to cough near them. Seek medical attention if you develop a cough that persists
for more than three weeks.
Q- What Is Typhoid (Enteric) Fever?
Ans- Typhoid (Enteric) Fever
Typhoid Fever is an acute illness
associated with diarrhea, systemic disease, fever and rash caused by the
Salmonellae typhi bacteria.
Causes
·
Typhoid Fever is contracted by the
ingestion of the bacteria in contaminated food or water. Patients with acute
illness can contaminate the surrounding water supply through the stool, which
contains a high concentration of the bacteria. The bacteria multiply in the
gallbladder, bile ducts, or liver and passes into the bowel. The bacteria can
survive for weeks in water or dried sewage. Following ingestion, the bacteria
spread from the intestine via the bloodstream to the intestinal lymph nodes,
liver, and spleen via the blood where they multiply.
·
Salmonella may directly infect the
gallbladder through the hepatic duct or spread to other areas of the body
through the bloodstream.
·
A few people can become carriers of S.
typhi and continue to shed the bacteria in their feces
Symptoms
·
The incubation period is usually 1-2
weeks and the duration of the illness is about 4-6 weeks.
·
Early symptoms are generalized and
include fever, malaise and abdominal pain. As the disease progresses, the fever
becomes higher (greater than 103 degrees Fahrenheit), and diarrhea becomes
prominent. Weakness, profound fatigue, delirium, and an acutely ill appearance
develop.
·
A rash, characteristic only of typhoid
and called "rose spots," appears in some cases of typhoid. Rose spots
are small (1/4 inch) red spots that appear most often on the abdomen and
chest.Chest congestion, abdominal pain and discomfort are common. The fever
becomes constant.
·
Improvement occurs in the third and
fourth week in those without complications. There is a chance of recurrent
symptoms (relapse) after feeling better for one to two weeks. Relapses are
actually more common in individuals treated with antibiotics.Typically,
children have milder disease and fewer complications than adults.
Diagnosis
·
An elevated white blood cell count in
blood
·
A blood culture during first week of
the fever can show S. typhi bacteria
·
A stool culture
·
An ELISA test on urine may show Vi
antigen specific for the bacteria
·
A platelet count (decreased platelets )
·
A fluorescent antibody study
(demonstrates Vi antigen, which is specific for typhoid)
Treatment
Intravenous fluids and electrolytes may
be given. Appropriate antibiotics aregiven to kill the bacteria. There are
increasing rates of antibiotic resistance throughout the world, so the choice
of antibiotics should be a careful one.
Prognosis
The illness usually resolves in 2 to 4
weeks with treatment. The outcome is likely to be good with early treatment,
but becomes poor if complications develop. Cases in children are milder, and
are more debilitating in the elderly. Relapse may occur if the treatment has
not fully eradicated the infection.
Possible complications
·
Intestinal hemorrhage (severe GI
bleeding)
·
Intestinal perforation
·
Kidney failure
·
Peritonitis
Prevention
·
Vaccines are recommended during
epidemic outbreaks.
·
Immunization is not always completely
effective and at-risk travelers should drink only boiled or bottled water and
eat well cooked food. Experimentation with an oral live attenuated typhoid
vaccine is now underway and appears promising.
Adequate water treatment, waste disposal, and
protection of food supply from contamination are important public health
measures. Carriers of typhoid must not be allowed to work as food handlers.
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