Staphylococcal infections

Staphylococcal (staph) infections are communicable conditions caused by certain bacteria and generally characterized by the formation of abscesses. They are the leading cause of infections originating in hospitals in the United States.

Classified since the early 20th century as among the deadliest of all disease-causing organisms, staph exists on the skin or inside the nostrils of 20% to30% of healthy people. The bacteria are sometimes found in breast tissue, the mouth, and the genital, urinary, and upper respiratory tracts.

Although staph bacteria are usually harmless, when injury or a break in the skin enables the organisms to invade the body and overcome the body's naturaldefenses, consequences can range from minor discomfort to death. Infection ismost apt to occur in:

  • Newborns
  • Women who are breastfeeding
  • Individuals whose immune systems have been impaired by radiation chemotherapy, or medication
  • Intravenous drug users
  • Those with surgical incisions, skin disorders, and serious illnesses such as classify term="Cancer" type="print-hyplink">cancer, diabetes, or lung disease.

Staph infections produce pus-filled pockets (abscesses) located just beneaththe surface of the skin or deep within the body. The risk of infection is greatest among the very young and the very old.

A localized staph infection is confined to a ring of dead and dying white blood cells and bacteria. The skin above the infection feels warm to the touch.Most of these abscesses eventually burst, and the pus that leaks onto the skin can cause new infections.

A small fraction of localized staph infections enter the bloodstream and spread through the body. In children, these body-wide infections often affect theends of the long bones of the arms or legs, causing a bone infection calledosteomyelitis. When adults develop invasive staph infections, bacteria are most apt to cause abscesses of the brain, heart, kidneys, liver, lungs, or spleen.

Named for the golden color of the bacteria grown under laboratory conditions,S. aureus is a hardy organism that can survive in extreme temperatures or other inhospitable circumstances. About 70% to 90% of the population carry this strain of staph in the nostrils at some time. Although present on theskin of only 5% to 20% of healthy people, as many as 40% carry it elsewhere(such as in the throat, vagina, or rectum) for varying periods of time from hours to years without developing symptoms or becoming ill.

S. aureus flourishes in hospitals, where it infects staff and surgicalpatients; those who have skin irritations, insulin-dependent diabetes, kidney disease, or who receive frequent allergy-desensitization injections. Staphbacteria also can contaminate bedclothes, catheters, and other objects.

S. aureus causes a variety of infections. Boils and inflammation of the skin surrounding a hair shaft are the most common. Toxic shock (TSS) and scalded skin syndrome (SSSS) are among the most serious.

Toxic shock syndrome is a life-threatening infection characterized by severeheadache, sore throat, fever as high as 105°F, and a sunburn-like rash that spreads from the face to the rest of the body. Symptoms appear suddenly; they also include dehydration and watery diarrhea.

Inadequate blood flow to peripheral parts of the body (shock) and loss of consciousness occur within the first 48 hours. Between the third and seventh dayof illness, skin peels from the palms of the hands, soles of the feet, and other parts of the body. Kidney, liver, and muscle damage often occur.

Rare in adults and most common in newborns and other children under the age of five, scalded skin syndrome originates with a localized skin infection. A mild fever and/or an increase in the number of infection-fighting white bloodcells may occur. A bright red rash spreads from the face to other parts of the body and eventually forms scales. Large, soft blisters develop at the siteof infection and elsewhere. When they burst, they expose inflamed skin that looks as if it had been burned.

S. aureus can also cause:

  • Arthritis
  • Bacteria in the bloodstream
  • Pockets of infection and pus under the skin
  • Tissue inflammation that spreads below the skin, causing pain and swelling
  • Inflammation of the valves and walls of the heart
  • Inflammation of tissue that enclosed and protects the spinal cord and brain (meningitis)
  • Inflammation of bone and bone marrow
  • Pneumonia.

Capable of clinging to tubing (as in that used for intravenous feeding, etc.), prosthetic devices, and other non-living surfaces, S. epidermidis is the organism that most often contaminates devices that provide direct access to the bloodstream.

The primary cause of bacteremia in hospital patients, this strain of staph ismost likely to infect cancer patients, whose immune systems have been compromised, and high-risk newborns receiving intravenous supplements.

S. epidermidis also accounts for two of every five cases of inflammation of prosthetic heart valves. This is a complication of the implantation ofan artificial valve in the heart. Although contamination usually occurs during surgery, symptoms of infection may not become evident until a year after the operation. More than half of the patients who develop this condition die.

Existing within and around the urethra (the tube-like structure that carriesurine from the bladder) of about 5% of healthy males and females, S. saprophyticus is the second most common cause of unobstructed urinary tract infections (UTIs) in sexually active young women. This strain of staph is responsible for 10% to 20% of infections affecting healthy outpatients.

Staph bacteria can spread through the air, but infection is almost always theresult of direct contact with open sores or body fluids contaminated by these organisms. Staph bacteria often enter the body through inflamed hair follicles or oil glands. Or they penetrate skin damaged by burns, cuts and scrapes,infection, insect bites, or wounds.

Multiplying beneath the skin, bacteria infect and destroy tissue in the areawhere they entered the body. Staph infection of the blood develops when bacteria from a local infection infiltrate the lymph glands and bloodstream. Theseinfections, which can usually be traced to contaminated catheters or intravenous devices, usually cause persistent high fever and sometimes shock. They also can cause death within a short time.

Common symptoms of staph infection include:

  • Pain or swelling around acut, or an area of skin that has been scraped
  • Boils or other skin abscesses
  • Blistering, peeling, or scaling of the skin. This is most common in infants and young children.
  • Enlarged lymph nodes in the neck, armpits, or groin.

A family doctor should be notified whenever:

  • Lymph nodes in the neck,armpits, or groin become swollen or tender
  • An area of skin that hasbeen cut or scraped becomes painful or swollen, feels hot, or produces pus. These symptoms may mean the infection has spread to the bloodstream.
  • Aboil or carbuncle appears on any part of the face or spine. Staph infectionsaffecting these areas can spread to the brain or spinal cord.
  • A boilbecomes very sore. Usually a sign that infection has spread, this conditionmay be accompanied by fever, chills, and red streaks radiating from the siteof the original infection.
  • Boils which develop repeatedly. This typeof recurrent infection could be a symptom of diabetes.

Blood tests that show very high concentrations of white blood cells can suggest a staph infection, but diagnosis is verified after lab analysis of material removed from pus-filled sores, and of normally-uninfected body fluids suchas blood and urine. X-rays can help doctors find internal abscesses and estimate the severity of infection. Needle biopsy (removing tissue with a needle,then examining it under a microscope) may be used to find out if the bones are affected.

Mild staph infections can generally be cured by keeping the area clean, usingsoaps that leave a germ-killing film on the skin, and applying warm, moist compresses to the affected area for 20 to 30 minutes three or four times a day. Severe or recurrent infections may require a 7- to 10-day course of treatment with penicillin or other oral antibiotics. The precise antibiotic prescribed depends on the location of the infection and the type of bacteria involved

In case of a more serious infection, antibiotics may be administered intravenously for as long as six weeks. Intravenous antibiotics are also used to treat staph infections around the eyes or on other parts of the face. Surgery maybe required to drain or remove abscesses that form on internal organs, or onshunts or other devices implanted inside the body.

Most healthy people who develop staph infections recover fully within a shorttime. Others develop repeated infections. Some become seriously ill, requiring long-term therapy or emergency care. A small percentage die.

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