BACTERIOSTATIC
Some of these bacteria are aerobic (they
need oxygen to grow and multiply) and
are therefore most commonly found on
the skin or within the respiratory sys-
tem.
Others
are
anaerobic,
thriving
where there is no oxygen, deep within
tissue or wounds.
Some types of bacteria are naturally
static; if they move around the body at
all, they do so only when carried in
currents of air or fluid. However, there
are also highly motile types of bacteria,
such as salmonella, which move through
fluids by lashing with their whiplike
tails (known as flagella) and can anchor
themselves to other cells with filamen-
tous threads called pili.
REPRODUCTION
Bacteria reproduce by simple cell divi-
sion, which can occur every few minutes
in ideal conditions (exactly the right
temperature and sufficient nourishment
for all cells). Some bacteria multiply by
each producing a spore (a single new
bacterium). Spores, which are protected
by a tough membrane, can survive high
temperatures, dry conditions, and lack
of nourishment.
HOW BACTERIA ENTER THE BODY
Bacteria can enter the body through the
lungs if they are inhaled in infected
droplets spread by coughs and sneezes.
The digestive tract may become infected
if contaminated food is eaten. Some
bacteria cause diseases, such as sexually
transmitted infections, by entering the
genitourinary system.
Bacteria can also penetrate the skin in
various ways: through hair follicles; by
way of superficial cuts and abrasions;
through burns; and via deep, pene-
trating wounds.
HOW BACTERIA CAUSE DISEASE
Some bacteria release poisons (toxins)
that are harmful to human cells. The
toxins either destroy the cell or disrupt
its chemical processes. Less commonly,
certain types of bacteria directly enter,
and multiply within, body cells, causing
tissue damage as they spread.
THE BODY'S DEFENCES
The body’s first defences against dis-
ease-causing bacteria are the skin and
the
mucous membranes
lining the res-
piratory tract, the digestive tract, and
the genitourinary system. The eyes are
protected by an
enzyme
in tears and
the stomach secretes hydrochloric acid,
which kills many of the bacteria found
in food and water.
If bacteria pass through these barriers,
the body’s
immune system
responds by
sending various types of white blood
cell to seek and destroy the bacteria.
Immunity can also be generated by
immunization.
This involves injecting a
weakened form of the bacterium or its
poison into the body to stimulate an
immune response. Immunization is now
routine for a number of conditions,
including
diphtheria, tetanus,
and some
forms of
meningitis.
TREATMENT OF BACTERIAL DISEASES
The immune response is sometimes
enough to bring about recovery, and
mild bacterial infections may not need
any treatment. However,
antibiotic drugs
are the main form of treatment for more
severe infections.
Superficial infected
wounds may be treated with
antiseptics.
Some bacteria, such as
MRSA,
are now
becoming resistant to treatment with
antibiotics. In these circumstances, bac-
terial infections can be difficult or even
impossible to treat and may be life-
threatening. (See also
infectious disease.)
bacterial endocarditis
See
endocarditis
.
bacterial food poisoning
See
food poisoning
.
bacterial vaginosis
An infection of the
vagina
that causes a
greyish-white
discharge
and itching.
The disorder is due to excessive growth
of
bacteria
that normally live in the
vagina. Bacterial vaginosis occurs most
commonly in sexually active women
and is treated with
antibiotic drugs
.
bactericidal
A term that is used to describe any
substance that kills bacteria. (See also
antibiotic drugs; bacteriostatic.)
bacteriology
The study of
bacteria,
particularly of the
types that cause disease. Bacteriology
includes techniques used to isolate and
identify bacteria from specimens such
as a throat swab or urine. Bacteria are
identified by their appearance under a
microscope, including their response to
stains (see
Gram’s stain; staining),
and by
the use of
culture.
Testing for sensitivity
to
antibiotic drugs
may be performed.
bacteriostatic
A term used to describe a substance that
stops the growth or multiplication of
bacteria
but does not kill them. (See also
antibiotic drugs; bactericidal.)
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