Staphylococcal infections

Definition

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

Description

Classified since the early twentieth century as among the deadliest of all disease-causing organisms, staphylococcal bacteria exist on the skin or inside the nostrils of 20 to 30 percent of healthy people. It is sometimes found in breast tissue, the mouth, and the genital, urinary, and upper respiratory tracts.

Staph bacteria are usually harmless; however, when an injury or a break in the skin enables the organisms to invade the body and overcome the body's natural defenses, consequences can range from minor discomfort to death.

Demographics

Infection is most apt to occur in newborns; children whose immune systems have been undermined by radiation treatments, chemotherapy , or medication; those with surgical incisions or skin disorders; and among people with serious illnesses such as cancer , diabetes, and lung disease. Children are also more at risk for staph infections if they have HIV/AIDS or other diseases that compromise immune function, have a catheter or implanted prosthetics, are hospitalized, have open wounds , or live in close quarters with a large group of others. It is not clear exactly how many staph infections occur each year, but it is the most common infection that begins in the hospital.

Causes and symptoms

Staph infections produce pus-filled pockets (abscesses) located just beneath the surface of the skin or deep within the body. A localized staph infection is confined to a ring of dead and dying white blood cells and bacteria. The skin above it feels warm to the touch. Most of these abscesses eventually burst, and 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 systemic (affecting the whole body) or disseminated infections frequently affect the ends of the long bones of the arms or legs, causing a bone infection called osteomyelitis. Other abscesses that can develop from staph infection include those of the brain, heart, kidneys, liver, lungs, or spleen.

Staphylococcus aureus

Named for the golden color of the bacteria grown under laboratory conditions, Staphylococcus aureus is a hardy organism that can survive in extreme temperatures or other inhospitable circumstances. About 70 to 90 percent of the population carry this type of staph in their nostrils at some time in their lives. Although present on the skin of only 5 to 20 percent of healthy people, as many as 40 percent of individuals 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 healthcare personnel and infects patients who have had surgery, have open wounds, have acute dermatitis , insulin-dependent diabetes, or dialysis-dependent kidney disease, or who receive frequent allergy-desensitization injections. Staph bacteria can also contaminate bedclothes, catheters, and other objects.

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

TOXIC SHOCK Toxic shock syndrome is a life-threatening infection characterized by severe headache , sore throat , fever as high as 105°F (40.5°C), 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 day of 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.

SCALDED SKIN SYNDROME 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 blood cells 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 site of infection and elsewhere. When they burst, they expose inflamed skin that looks as if it had been burned.

MISCELLANEOUS INFECTIONS S. aureus can also cause the following:

• arthritis
• bacteria in the bloodstream (bacteremia)
• pockets of infection and pus under the skin (carbuncles)
• tissue inflammation that spreads below the skin, causing pain and swelling (cellulitis)
• inflammation of the valves and walls of the heart (endocarditis)
• inflammation of tissue that encloses and protects the spinal cord and brain (meningitis)
• inflammation of bone and bone marrow (osteomyelitis)
• pneumonia

Other strains of staphylococci

S. EPIDERMIDIS Capable of clinging to tubing (such as that used for intravenous feeding), 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 bacterial infection in hospital patients, this strain of staph is most 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 prosthetic valve endocarditis. Prosthetic valve endocarditis is inflammation that occurs as a complication of the implantation of an 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 prosthetic valve endocarditis die.

Causes and symptoms

Staph bacteria can spread through the air, but infection is almost always the result 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 area where they entered the body. Staph infection of the blood (staphylococcal bacteremia) develops when bacteria from a local infection infiltrate the lymph glands and bloodstream. These infections, which can usually be traced to contaminated catheters or intravenous devices, cause persistent high fever. They may cause shock. They also can cause death within a short time.

When to call the doctor

The following are common symptoms of staph infection:

• pain or swelling around a cut or an area of skin that has been scraped
• boils or other skin abscesses
• blistering, peeling, or scaling of the skin (This symptom is most common in infants and young children.)
• enlarged lymph nodes in the neck, armpits, or groin

A family physician should be notified whenever the following symptoms are present:

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

Diagnosis

Blood tests that show unusually high concentrations of white blood cells can suggest staph infection, but diagnosis is based on laboratory analysis of material removed from pus-filled sores and on analysis of normally uninfected body fluids such as blood and urine. Also, x-rays can enable doctors to locate 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 assess if any bones are infected.

Treatment

Superficial staph infections can generally be cured by keeping the area clean, using soaps 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 seven to 10 day course of treatment with penicillin or other oral antibiotics . The location of the infection and the identity of the causal bacteria determine which of several effective medications should be prescribed.

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 may be required to drain or remove abscesses that form on internal organs or on shunts or other devices implanted inside the body.

Alternative treatment

Alternative therapies for staph infection are meant to strengthen the immune system and prevent recurrences. Among the therapies believed to be helpful for the person with a staph infection are yoga (to stimulate the immune system and promote relaxation), acupuncture (to draw heat away from the infection), and herbal remedies. Herbs that may help the body overcome, or withstand, staph infection include the following:

• Garlic ( Allium sativum ). This herb is believed to have antibacterial properties. Herbalists recommend consuming three garlic cloves or three garlic oil capsules a day, starting when symptoms of infection first appear.
• Cleavers ( Galium aparine ). This anti-inflammatory herb is believed to support the lymphatic system. It may be taken internally to help heal staph abscesses and reduce swelling of the lymph nodes. A cleavers compress can also be applied directly to a skin infection.
• Goldenseal ( Hydrastis canadensis ). Another herb believed to fight infection and reduce inflammation, goldenseal may be taken internally when symptoms of infection first appear. Skin infections can be treated by making a paste of water and powdered goldenseal root and applying it directly to the affected area. The preparation should be covered with a clean bandage and left in place overnight.
• Echinacea ( Echinacea spp.). Taken internally, this herb is believed to have antibiotic properties and is also thought to strengthen the immune system.
• Thyme ( Thymus vulgaris ), lavender ( Lavandula officinalis ), or bergamot ( Citrus bergamot ) oils. These oils are believed to have antibacterial properties and may help to prevent the scarring that may result from skin infections. A few drops of these oils are added to water and then a compress soaked in the water is applied to the affected area.
• Tea tree oil ( Melaleuca spp.). Another infection-fighting herb, this oil can be applied directly to a boil or other skin infection.

Prognosis

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

Doctors and researchers are becoming increasingly concerned about staph infections that are resistant to antibiotics. A bacterium that is considered resistant is one that can no longer be treated effectively using the antibiotics that are commonly prescribed for that type of infection. Resistant staph infections can usually be treated effectively with other antibiotics. Children who are most at risk for resistant staph infections are those who have been in the hospital or have serious underlying medical conditions. According to the Centers for Disease Control, although it is not clear how many cases of resistant staph infections occur each year, they are thought to be very rare. They recommend treating all infections promptly and only prescribing antibiotics when there is an underlying bacterial cause for the disease (antibiotics are not effective against viruses) to help reduce the occurrence of bacteria becoming resistant to antibiotics.

Prevention

Healthcare providers and patients should always wash their hands thoroughly with warm water and soap after treating a staph infection or touching an open wound or the pus it produces. Pus that oozes onto the skin from the site of an infection should be removed immediately. This affected area should then be cleansed with antiseptic or with antibacterial soap.

To prevent infection from spreading from one part of the body to another, it is important to shower rather than bathe during the healing process. Because staph infection is easily transmitted from one member of a household to others, towels, washcloths, and bed linens used by someone with a staph infection should not be used by anyone else. They should be changed daily until symptoms disappear, and laundered separately in hot water with bleach. Children should frequently be reminded not to share brushes, combs, or hair accessories.

Parental concerns

Staph infections are most likely to occur after a child has had surgery or a wound of some kind. A good way to help prevent staph infections of wounds is to keep the wound clean and dry. Children who have staph infections, especially skin infections, should be kept away from others whom they are likely to infect, and their bedding, clothes, and other things that may have touched the wound should be cleaned with hot soapy water and bleach.

Resources

BOOKS

Honeyman, Allen, Herman Friedman, and Mauro Bendinelli, eds. Staphylococcus Aureus Infection and Disease. New York: Kluwer Academic, 2001.

PERIODICALS

Zoler, Mitchell L. "Community-Acquired MRSA Infections Rising: Pediatric, Soft Tissue Infections." Family Practice News 34, no. 11 (June 2004): 7–8.

Tish Davidson, A.M. Maureen Haggerty