Staphylococcal Infections Health Article

Definition

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

Description

Classified since the early twentieth century as among the deadliest of all disease-causing organisms, staph exists on the skin or inside the nostrils of 20% to 30% of healthy people. It is sometimes found in breast tissue and the mouth, as well as 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, consequences can range from minor discomfort to death. Infection is most likely to occur in:

• newborns
• women who are breastfeeding
• individuals whose immune systems have been compromised by radiation treatment, chemotherapy, or medication
• intravenous drug users
• patients with surgical incisions, skin disorders, and serious illness such as cancer, diabetes, and lung disease

Types of infections

Staph infections produce pus-filled abscesses located just beneath the surface of the skin or deep within the body. 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 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. When adults develop disseminated staph infections, bacteria are most apt to infect the brain, heart, kidneys, liver, lungs, or spleen.

There are three staphylococcal species that commonly cause infections: Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus saprophyticus.

Staphylococcus aureus

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. Staph aureus is present (colonizes) on the skin of 5% to 20% of healthy people. As many as 40% carry it elsewhere, such as in the throat, vagina, or rectum, for periods of time varying from hours to years without developing symptoms or becoming ill. These individuals may be called asymptomatic carriers.

S. aureus flourishes in hospitals, where it colonizes in health care personnel and postoperative patients along with those who have acute dermatitis, insulin-dependent diabetes, dialysis-dependent kidney disease; or patients who receive frequent allergy-desensitization injections. Staph bacteria can also contaminate bedclothes, catheters, and other objects.

S. aureus causes a variety of infections. Folliculitis, a condition characterized by boils and inflammation of the skin surrounding a hair shaft, is the most common. Toxic shock and scalded skin syndromes are among the most serious.

TOXIC SHOCK. Toxic shock syndrome is a life-threatening infection characterized by sudden onset of symptoms: severe headache, 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 also may include dehydration and watery diarrhea.

Shock (inadequate blood flow to peripheral parts of the body) 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 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:

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