Staphylococcal Infections

Staphylococcal (stah-fih-lo-KAH-kul) infections are infections caused by the organism Staphylococcus aureus (stah-fih-lo-KAH-kus ARE-ree-us) and related species of bacteria, over 30 species in all.

What Are Staphylococcal Infections?

They cannot be seen with the naked eye, but bacteria * cover the skin's surface. Staphylococcus aureus (S. aureus) bacteria, also called staph (pronounced staff) bacteria, often live on people's skin, particularly around openings such as the nose, mouth, genitals * , and anus * , and sometimes inside the nose and mouth, without causing disease. However, when a person's skin is broken or cut, the bacteria can enter the wound and cause an infection. Staph infections range from minor skin infections to joint, bone, or lung infections to widespread or systemic infections that can be life-threatening. Some strains * of staph produce a toxin (or poison) that causes illness.

Newborns, elderly people, and people with immune systems * weakened by diseases such as cancer and AIDS * are at greater risk of serious staph infections. Some serious infections, often resistant to many antibiotics * , can be acquired in a hospital when a patient is being treated for another condition. In fact, in the United States, staph infections are considered the leading cause of primary infections that result from being medically treated within hospitals and healthcare centers. Such infections are called nosocomial (nas-eh-KO-meh-el) infections.

How Common Are Staphylococcal Infections?

Digitally-colorized scanning electron micrograph of Staphylococcus aureus bacteria.

Digitally-colorized scanning electron micrograph of Staphylococcus aureus bacteria. One form of Staphylococcus aureus bacteria known as methicillin-resistant Staphylococcus aureus, or MRSA, causes a range of illnesses, from skin and wound infections to pneumonia and bloodstream infections that can cause sepsis and death.
National Institute of Allergy and Infectious Diseases (NIAID).

Overall, the incidence of staph infections steadily increased during the late 1990s and early 2000s in the United States and other developed countries. Globally, if left untreated, such infections as a group can potentially kill the majority of people afflicted. People more prone to staph infections and serious symptoms are more likely to die from such infections.

Are Staphylococcal Infections Contagious?

Sometimes staph infections of the skin are contagious. In such circumstances, they are called communicable (contagious) diseases because bacteria can be transmitted between humans. Infrequently, staph bacteria are spread through the air. However, they are usually transmitted by humanto-human contact. If a person touches another person who has a staph infection of the skin (with either open sores or bodily fluids), and then touches his or her own mouth, nose, or an area of broken skin, the staph infection can spread. A person also can spread the bacteria from one part of the body to another through touch. Staph can also be transmitted via contaminated surfaces and food.

What Are Some Types of Staphylococcal Infections?

Impetigo (im-pih-TEE-go) is a skin infection that usually occurs around the nose and mouth. In impetigo, fluid-filled blisters appear and often burst and form yellowish crusts of skin. Impetigo is a contagious infection that can spread if a person scratches the blisters and then scratches or touches another area of the body.

Carbuncles (KAR-bung-kulz) and furuncles (FYOOR-ung-kulz), also known as boils, are staph infections that produce a red swollen bump filled with pus * in the skin surrounding a hair follicle * . With boils, pus forms in a single hair follicle, whereas carbuncles form from grouped furuncles and have several small chambers like a series of connected boils.

Cellulitis (sel-yoo-LYE-tis) is an infection of the deeper layers of the skin and the connective tissues below the skin's surface. People with cellulitis usually have an area of red, swollen, tender, warm skin. They also may have fever, swollen lymph nodes * , and a general feeling of being sick. Cellulitis is most common on the face and lower legs.


Antibiotics are used widely to treat infections such as those caused by staph. Over time, staph bacteria may become stronger, so the antibiotics may not be as effective against the germ. This development is known as antibiotic resistance. When the Scottish biologist Alexander Fleming (1881–1955) discovered penicillin in 1928, staph bacteria were highly sensitive to it. By the early 2000s, few staph bacteria were killed by penicillin. These bacteria often are resistant to many antibiotics.

The more important strains of antibiotic-resistant staph are known as methicillin-resistant Staphylococcus aureus (MRSA). MRSA is resistant to commonplace antibiotics, but it is still susceptible to the more powerful medications of last resort. A more serious strain of staph infection, vancomycin-intermediate S. aureus (VISA), can resist vancomycin, one of the most powerful (and last-resort) antibiotics available. Although all strains of the bacterium found so far have been treatable with some type of antibiotic, VISA potentially could defy all medication available in the early 2000s to treat it. Fortunately, VISA is quite rare.

In the past, MRSA and VISA infections usually developed only in a hospital or healthcare facility where prolonged treatment of patients with several antibiotics is common. As of 2008, however, community-acquired MRSA (those infections within a local community but outside a health facility) was widespread, even in previously healthy individuals without a history of recent antibiotic treatments. In fact, the Centers for Disease Control and Prevention (CDC) states that approximately 12 percent of MRSA infections (throughout the United States) as of 2008 were community-associated, although the percentages varied widely depending on region. The spread of community-acquired MRSA alters its treatment, especially concerning the initial choices of antibiotics. As of 2016, the progression of MRSA is an ongoing health concern, still considered a serious public health problem; however, the CDC reported in 2013 that hospital-associated cases of MRSA have been steadily declining. Of utmost importance for anyone who may have MRSA is the need to get prompt medical attention for any and all skin and soft tissue infections.

Overall, the prudent use of antibiotics remains especially important as more bacterial strains become more resistant to antibiotics.

In women who are breastfeeding their infants, an inflammation of the breast can develop. Called mastitis, the infection can cause bacteria to be released in the mother's milk, which can harm the child.

Toxic shock syndrome (TSS) is a severe infection that, like scalded skin syndrome, is caused by a toxin produced by staph bacteria. With initial symptoms of severe headache, high fever reaching 105°F (40.5°C), sore throat, and sunburn-looking rash, it can develop into a life-threatening condition when such symptoms as dehydration * and diarrhea * occur, followed by peeling skin over much of the body. Muscle, kidney, and liver damage can lead quickly to loss of life. TSS was first recognized in the late 1970s and early 1980s, mostly among women who were using certain types of very absorbent tampons, but it can occur in people of both sexes and in both children and adults. After this type of absorbent tampon was no longer available, TSS usually developed after surgery or in wounds that in most cases did not look infected but contained the toxin-producing staph. Skin abscesses * or other staphylococcal infections may also lead to TSS. Symptoms of TSS include sudden fever, low blood pressure, very red rash, vomiting, diarrhea, and muscle pain.

Staph bacteria can produce other types of toxins that cause food poisoning when a person eats contaminated food (usually meats, poultry, eggs, and dairy products) that has not been heated or refrigerated at the proper temperature. Symptoms include belly pain, nausea (NAW-zee-uh), and vomiting. If the food poisoning is severe, a person may experience headaches, muscle aches, and blood pressure changes.

Some staph infections affect internal organs. Staph is a common cause of the bone infection osteomyelitis (ah-stee-o-my-uh-LYE-tis). Staph infections also may cause pneumonia (nu-MO-nyah), an inflammation of the lungs; blood infection (sepsis); and, more rarely, meningitis (meh-nin-JY-tis), an inflammation of the membranes that cover the brain and the spinal cord (the meninges, meh-NIN-jeez). The bacteria may spread from an infection elsewhere in the body, or they can come from a medical device, such as a catheter * , that has been colonized * by staph bacteria. Staphylococcus aureus also may infect the heart valves, where it causes inflammation * and gives rise to a condition called endocarditis (endo-kar-DYE-tis).

How Is a Staphylococcal Infection Diagnosed?

A doctor may diagnose and treat a staph infection based on its appearance, but a definite diagnosis is made by identifying the organism under a microscope or by culture *

What Is the Treatment for Staphylococcal Infections?

Minor skin infections caused by staph bacteria often can be treated with an over-the-counter antibiotic ointment, or they can heal on their own. The choice of the antibiotic often depends on the severity of the infection, its location, and the susceptibility * of the particular staph strain. If a person has an abscess that stems from a staph infection, surgery to drain the pus may be necessary in addition to antibiotics in order to allow the infection to heal.

More serious staph infections, such as endocarditis, osteomyelitis, TSS, and scalded skin syndrome, usually require hospitalization and supportive care, such as antibiotics, intravenous * fluids to prevent dehydration, and other medications. Endocarditis caused by staph may require surgery in which the damaged heart valve is removed and an artificial valve is inserted. Scalded skin syndrome is treated with intravenous antibiotics so that the skin can be protected from becoming dehydrated and consequently peeling off.

Because antibiotics are used widely to treat both minor and serious infections caused by staph and other bacteria, some strains of bacteria have become resistant to common antibiotics. Discovery of new medications and forms of treatment are important, and scientists continue to work on developing a Staphylococcus aureus vaccine that might help people with weakened immune systems resist staph infections.

How Long Does a Staphylococcal Infection Last?

Minor skin infections caused by staph bacteria usually clear up within a week, whereas more serious widespread illnesses may take several weeks to more than a month to resolve.

What Are the Complications of Staphylococcal Infections?

Minor staph skin infections rarely result in complications, but some can produce more widespread infection, such as sepsis, a serious systemic infection caused by bacteria invading the bloodstream. TSS can lead to shock * , organ failure, and death. Scalded skin syndrome can give rise to other infections, dehydration, and sepsis. Osteomyelitis can cause permanent bone damage and may require surgical treatment. Under normal circumstances, healthy patients recover fully from staph infections within a short period. However, even healthy people can develop repeat infections, which can eventually become more serious.

Can Staphylococcal Infections Be Prevented?

There are several ways to help prevent the spread of staph infections:

Food poisoning can be prevented by washing hands before food preparation, storing food properly before cooking, cooking food to the appropriate temperatures, using clean utensils and dishes, and refrigerating or freezing food as soon as possible after cooking. To lessen the risk of TSS, women are advised to use less absorbent tampons and to change them frequently, as well as not to use tampons exclusively during a menstrual period or to avoid tampons altogether.

See also Antibiotic Resistance • Bacterial Infections • Endocarditis, Infectious • Food Poisoning • Impetigo • Meningitis • Osteomyelitis • Pneumonia • Sepsis • Skin and Soft Tissue Infections • Sports Injuries: Overview • Toxic Shock Syndrome • Wounds


Books and Articles

Baorto, Elizabeth P. “Staphylococcus Aureus Infection.” Medscape, June 30, 2016. (accessed July 12, 2016).

Barrett, Ron and George J. Armelagos. An Unnatural History of Emerging Infections. New York: Oxford University Press, 2014.


California Department of Public Health. “Community-Associated (CAMRSA)/Staph Infections: A Guideline for Athletic Departments.” (accessed July 12, 2016). . “Staphylococcus.” U.S. Department of Health and Human Services. (accessed July 12, 2016).

MedlinePlus. “Staphylococcal Infections.” U.S. National Library of Medicine. (accessed July 12, 2016).


Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 888-674-6854. Website: (accessed July 12, 2016).

National Institute of Allergy and Infectious Diseases. Office of Communications and Public Liaison, 5601 Fishers Lane, MSC 9806, Bethesda, MD 20892. Toll-free: 866-284-4107. Website: (accessed July 12, 2016).

* bacteria (bak-TEER-ee-a) are single-celled microorganisms which typically reproduce by cell division. Some, but not all, types of bacteria can cause disease in humans. Many types can live in the body without causing harm.

* genitals (JEH-nih-tuls) are the external sexual organs.

* anus is the opening at the end of the digestive system through which waste leaves the body.

* strains are various subtypes of organisms, such as viruses or bacteria.

* immune system (im-YOON) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.

* AIDS, (or Acquired Immunodeficiency (ih-myoo-no-dih-FIH-shen-see) Syndrome, is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).

* antibiotics (an-tie-by-AH-tiks) are drugs that kill or slow the growth of bacteria

* pus is a thick creamy fluid, usually yellow or ivory in color, that forms at the site of an infection. Pus contains infection-fighting white cells and other substances.

* hair follicle (FAH-lih-kul) is the skin structure from which hair develops and grows.

* lymph nodes (LIMF) are small bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.

* dehydration (dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive and unre-placed loss of body fluids, such as through sweating, vomiting, or diarrhea.

* diarrhea (di-ah-RE-a) refers to frequent watery stools (bowel movements).

* abscesses (AB-seh-sez) are localized or walled-off accumulations of pus caused by infection that can occur anywhere within the body.

* catheter (KAH-thuh-ter) is a small plastic tube placed through a body opening into an organ (such as the bladder) or through the skin directly into a blood vessel. It is used to give fluids to or drain fluids from a person.

* colonized means that a group of organisms, particularly bacteria, are living on or inside the body without causing symptoms of infection.

* inflammation (in-fla-MAY-shun) is the body's reaction to irritation, infection, or injury and involves swelling, pain, redness, and warmth.

* culture (KUL-chur) is a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days the organisms will grow and can be identified.

* susceptibility (su-sep-ti-BIL-i-tee) means having less resistance to and higher risk for infection or disease.

* intravenous (in-tra-VEE-nus), or IV, means within or through a vein. For example, medi-cations, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.

* shock is a serious condition in which blood pressure is very low and not enough blood flows to the body's organs and tissues. Untreated, shock may result in death.

  This information is not a tool for self-diagnosis or a substitute for professional care.