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 40єF, and the freezer temperature is 0єF.

• 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.