Information on Infection
An
infection is the detrimental colonization of a human
or animal body by a foreign species. An infection is a war
in which the infecting organism seeks to utilize the human
or animal resources in order to multiply at the expense of
the host. The infecting organism, or pathogen, interferes
with the normal functioning and perhaps the survival of the
host.
Since
we know drugs and diseases that can decrease the normal body
defenses against infection and the types of infection likely
to occur in patients, most types of infection are potentially
preventable and often treatable.
Bacterial
Infections
Bacteria
are an ancient form of life, quite different from the eukaryotes
(which includes the fungi, plants and animals). They are small
cells, found in the environment as either individual cells
or aggregated together as clumps, and their intracellular
structure is simple. Bacteria multiply by binary fission and
there is no sexual interaction.
The
human body is not sterile - presence of bacteria does not
equal disease. The gastric tract and surfaces exposed to the
external environment, such as the skin, vagina and upper respiratory
tract, are teeming with bacteria, most of which are either
harmless or positively beneficial.
Viral
Infections
Viruses
are small, obligate intracellular parasites which cause infection
by invading cells of the body and multiplying within them.
Within their life cycle they have a relatively short extracellular
period, prior to infecting the cells, and a longer intracellular
period during which they undergo replication. The human immune
system has mechanisms which can attack the virus in both these
phases of its life cycle, and which involve both non-specific
and specific mechanisms.
Natural
Defense Mechanisms against Infection
In
view of our constant exposure to micro-organisms we still
enjoy long infection-free periods and infections are the exception
rather than the rule. This resistance (immunity) of
our body to invasion, is a characteristic which is present
from birth, and is therefore called innate or natural immunity.
Following recovery from certain infections with a particular
micro-organism, individuals will never again develop infection
with the same organism. This form of protection is called
Acquired, Adaptive or Specific Immunity and an individual
is said to be immunised against that organism.
The
human body's defense against infection includes:
-
Skin
and Mucous membranes: The skin is the largest organ
in the body and our first line of defense against infection.
Any break in the skin is a potential site of infection.
-
Thymus:
Is a small glandular organ that is situated behind the
top of the breastbone. It consists mainly of lymphatic
tissue and serves as a storage place for T cells of the
immune system
-
Lymph
Nodes: These are small collections of infection fighting
cells that exist in chains along the course of the large
blood vessels of the body. There are hundreds of lymph
nodes throughout the body. These nodes filter lymph fluid,
removing foreign substances such as bacteria that get
trapped in their web-like structure. Then the infection
fighting cells such as macrophages, antibodies, and T
cells can destroy them.
-
Spleen:
The spleen is located in the upper left side of the abdomen.
It has many infection fighting functions such as filtering
out foreign organisms, removing old or damaged cells,
helping form some types of white blood cells.
-
Bone
marrow: This is located in the center of the bones
of the body particularly in the bones of the spine, ribs,
breast bone, pelvis and upper arms and legs. It is the
principal site for production of blood cells.
-
White
Blood Cells: Infection fighting cells of the immune
system, particularly the White Blood Cells
(WBC). When your white blood cell count is low there is
an increased risk of infection. There are five main types
of WBC's - lymphocytes (B and T cells), macrophages, basophils,
eosinophils and neutrophils.
Prevention
of Infection
Infection
cannot be completely prevented. However, there are things
you can do to decrease the risk of infection. Most bacterial
types of infection result from your body's inability to fight
off normal bacteria present in your gastrointestinal tract
or skin. Bacterial infection does not commonly result from
being in a crowded place. However, types of viral infections
such as colds and flu are common and are transmitted easily
from other people.
-
Avoid, if possible tightly crowded places during the height
of the cold/flu season. Generally a mask will not offer
much protection from infection, so it is better to avoid
close contact with people coughing and sneezing.
-
Wash
your hands often. For example After frequent handshaking,
Before preparing food, After touching raw meat, Before
eating, After using the restroom, After changing a baby's
diaper, After touching animals such as dogs or cats
-
Keep
your body clean by showering or bathing daily. If your
skin becomes dry, use lotion or oil to soften your skin
and prevent cracking.
-
Avoid
injury, even small cuts or tears in the skin could be
a susceptible site for infection. Wear shoes or slippers
to protect your feet from injury and/or infection.
-
Keep
your mouth clean by brushing your teeth twice daily. Use
soft toothbrush and mouth rinses.
-
Keep
raw meat, poultry, eggs, and seafood away from ready-to-eat
foods. Do not place cooked food on an unwashed plate where
raw meat, poultry, eggs, or seafood has been placed earlier.
-
Cook
food well. Use a food thermometer to check the internal
temperature. Cook meat until it is no longer pink and
the juices are no longer clear. Cook eggs until they are
firm. Bring sauces, soups, and gravies to a boil when
reheating.
-
Refrigerate
leftovers within 2 hours and make sure the refrigerator
temperature is no higher than 40ºF, and the freezer temperature
is 0ºF.
-
Never
thaw food at room temperature; thaw food in the refrigerator.
-
Thoroughly
wash all fruits and vegetables.
-
Avoid
contact with reptiles such as snakes, lizards, and turtles
because of the risk of salmonellosis.
-
Avoid
cleaning fish tanks because of possible exposure to Mycobacterium
marinum.
-
Avoid
an environment where mulch, hay, topsoil, etc. is being
"pitched" or spread. Inhalation of environmental spores,
particularly from moist, dark areas (e.g. compost piles)
may lead to infection and should be avoided.
-
Gloves
should be worn for contact with dirt and soil during gardening
and good hand washing after the gloves are removed is
essential.
-
Hot
tubs, saunas, and other communal baths are generally not
recommended. Bacteria and other microorganisms thrive
in warm water.
-
Those
who travel should avoid foods and beverages that may be
contaminated, particular raw fruits and vegetables, raw
or undercooked seafood or meat, tap water, ice made with
tap water, unpasteurized milk and dairy products, and
items sold by street vendors.
Foods
and beverages that are generally safe from infection include
steaming-hot foods, fruits that are peeled by the traveler,
bottled (especially carbonated) beverages, hot coffee
and tea, beer, wine, and water brought to a rolling boil
for 1 minute. Treatment of water with iodine or chlorine
may not be as effective as boiling but can be used when
boiling is not practical.
Treatment
of Infection
Prior
to the availability and application of antibiotics for the
control of diseases, gold salts, arsenicals, sulfa drugs and
other various chemicals were used to ward off the offending
bacterial pathogens. The clinical application of antibiotics
started in early 1940's when penicillin became available as
the first miracle drug created from a penicillium mold. A
few years later the broad spectrum tetracycline antibiotics
became available and their clinical use spread fast.
Antibiotics,
also known as antibacterials, are drugs used to treat
infections caused by bacteria. Antibiotics are medicines
that help your body fight bacteria, either by directly killing
the offending bugs or by weakening them so that your own immune
system can fight and kill them more easily.
Antibiotics
are used only to treat infections caused by bacteria; They
do not work against other organisms such as viruses or fungi.
It's important to bear this in mind if you think you have
some sort of infection, because many common illnesses, particularly
of the upper respiratory tract such as the common cold and
sore throats, are usually caused by viruses.
Most
bacterial cells have double layers on their outside. The outermost
layer -- the "cell wall" -- is similar to the outer layer
of plant cells, but is missing in human and animal cells.
This wall must grow along with the cell, or the growing cell
will eventually become too big for the wall and burst and
die. Antibiotics of the Penicillins and Cephalosporins
group kill bacteria by messing up the wall-building system.
Some
antibiotics can be used to treat a wide range of infections
and are known as 'broad-spectrum' antibiotics while
others which are only effective only against a few types of
bacteria are called 'narrow-spectrum' antibiotics. Some antibiotics
work against aerobic bacteria, that is organisms that need
oxygen to live, while others work against anaerobic bacteria,
organisms that don't need oxygen. Sometimes antibiotics are
given to prevent occurence of an infection, for example, before
certain operations. This is known as prophylactic use of antibiotics
and is common before surgery.
Antibiotics
are usually taken orally but can also be given by injection,
or applied topically to the affected part of the body such
as the skin, eyes or ears. The drugs begin to tackle most
infections within a few hours. It is vital to take the whole
course of treatment to prevent recurrence of the infection.
Sometimes
bacteria become 'resistant' to an antibiotic you have been
taking, meaning that the antibiotic drug will no longer
work. Resistance tends to occur when the bacterial infection
responsible for the symptoms is not completely cured, even
if the symptoms have cleared up. Some of the residual bacteria,
having been exposed to, but not killed by, the antibiotic
are more likely to grow into an infection that can survive
that particular antibiotic. This is why finishing the course
of antibiotics, even if you feel better, is very important.
Certain
antibiotics should not be taken with certain foods and drinks.
Some antibiotics are best taken when there is no food in your
stomach, usually an hour before meals or two hours after -
make sure you follow the instructions on the dispensing label.
Generally, it is not recommended to intake alcohol with any
kind of antibiotic. Do not take tetracyclines with dairy products,
as these can reduce the absorption of this type of antibiotic.
While
Antibiotics treat infections caused by bacteria, Antiviral
Drugs are compounds that are used to prevent or treat
viral infections, via the disruption of an infectious
mechanism used by the virus, or to treat the symptoms of an
infection. The various antiviral agents are designed
to thwart the replication of whatever virus they are directed
against.
One
means to prevent the virus replication is by blocking the
virus from commandeering the host cell's nuclear replication
machinery in order to have its genetic material replicated
along with the host's genetic material. The virus is not killed
directly. But the prevention of replication will prevent the
numbers of viruses from increasing, giving the host's immune
system time to deal with the stranded viruses.
Another
tact for antiviral drugs is to block a viral enzyme
whose activity is crucial for replication of the viral genetic
material. Still other antiviral drugs are directed at earlier
steps in the viral replication pathway. Antiviral therapy
also includes molecular approaches. The best example is the
use of oligonucleotides which are are sequences of nucleotides
that are specifically synthesized to be complimentary with
a target sequence of viral ribonucleic acid. By binding to
the viral RNA, the oligonucleotide blocks the RNA from being
used as a template to manufacture protein.
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