Staph Infection Slideshow Pictures MRSA Slideshow Pictures

Medical Author:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Superbug Staph Spread in Community

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: Barbara K. Hecht, PhD

MRSA, or methicillin-resistant Staphylococcus aureus, is a bacteriumthat can cause serious infections. It is resistant to numerous antibiotics of the beta-lactam family, including methicillinand penicillin.

MRSA belongs to the large group of bacteria known as Staphylococci, often referred to as Staph. About 25%-30% of all people have Staph within the nose, but it normally does not cause an infection. In contrast, only about 1% of the population have MRSA.

Infections with MRSA are most common in hospitals and other institutional health-care settings, such as nursing homes, where they tend to strike older people, those who are very ill, and people with a weakened immune system. In health-care settings, MRSA is a frequent cause of surgical wound infections, urinary tract infections, bloodstream infections (sepsis), and pneumonia.

MRSA outbreaks, however, are appearing increasingly in the community. Infections can occur in people who have not been hospitalized or had a medical procedure performed in the past year, and who do not have immune deficiency. These infections are termed community-associated MRSA infections (CA-MRSA). The U.S. Centers for Disease Control and Prevention(CDC) estimates that about 12% of MRSA infections are now community-associated, but this percentage can vary by community and patient population.

Learn about symptoms of MRSA infections »

What is Staphylococcus?

Staphylococcus is a group of bacteria that can cause a number of diseases as a result of infection of various tissues of the body. Staphylococcus is more familiarly known as Staph (pronounced "staff"). Staph-related illness can range from mild and requiring no treatment to severe and potentially fatal.

The name Staphylococcus comes from the Greek staphyle, meaning a bunch of grapes, and kokkos, meaning berry, and that is what Staph bacteria look like under the microscope, like a bunch of grapes or little round berries. (In technical terms, these are gram-positive, facultative anaerobic, usually unencapsulated cocci.)

Over 30 different types of Staphylococci can infect humans, but most infections are caused by Staphylococcus aureus. Staphylococci can be found normally in the nose and on the skin (and less commonly in other locations) of around 25%-30% of healthy adults and in 25% of hospital workers. In the majority of cases, the bacteria do not cause disease. However, damage to the skin or other injury may allow the bacteria to overcome the natural protective mechanisms of the body, leading to infection.

Who is at risk for Staph infections?

Anyone can develop a Staph infection, although certain groups of people are at greater risk, including newborn infants, breastfeeding women, and people with chronic conditions such as diabetes, cancer, vascular disease, and lung disease. Injecting drug users, those with skin injuries or disorders, intravenous catheters, surgical incisions, and those with a weakened immune system due either to disease or a result of immune suppressing medications all have an increased risk of developing Staph infections.

Staph infections are contagious until the infection has resolved. Direct contact with an infected sore or wound, or with personal-care items such as razors, bandages, etc., are common routes of transmission. Casual contact such as kissing or hugging does not pose a great risk for transmission if there is no direct contact with the infected area.

What are the symptoms and signs of a Staph infection?

Staphylococcal disease of the skin usually results in a localized collection of pus, known as an abscess, boil, or furuncle, depending upon the exact type of lesion that is present. The affected area may be red, swollen, and painful. Drainage or pus is common. When Staph is in the blood (bacteremia or sepsis), it can cause high fevers, chills, and low blood pressure.

What does a Staph infection look like?

What types of diseases are caused by Staph?

Skin infections (see above) are the most common type of disease produced by Staphylococcus. Staph infections of the skin can progress to impetigo (a crusting of the skin) or cellulitis (inflammation of the deeper layers of skin and connective tissue under the skin, leading to swelling and redness of the area). In rare situations, a serious complication known as scalded skin syndrome (see below) can develop. In breastfeeding women, Staph can result in mastitis (inflammation of the breast) or in abscess of the breast. Staphylococcal breast abscesses can release bacteria into the mother's milk.

When the bacteria enter the bloodstream and spread to other organs, a number of serious infections can occur. Spread of the organisms to the bloodstream is known as bacteremia or sepsis. Staphylococcal pneumonia predominantly affects people with underlying lung disease and can lead to abscess formation within the lungs. Infection of the heart valves (endocarditis) can lead to heart failure. Spread of Staphylococci to the bones can result in severe inflammation of the bones known as osteomyelitis. When Staph bacteria are present in the blood, a condition known as staphylococcal sepsis (widespread infection of the bloodstream) or staphylococcal bacteremia exists. Staphylococcal sepsis is a leading cause of shock and circulatory collapse, leading to death, in people with severe burns over large areas of the body. When untreated, Staph aureus sepsis carries a mortality (death) rate of over 80%. Although not common, Staph aureus has been reported as a cause of chorioamnionitis and neonatal sepsis in pregnancy, but group B streptococci are the most common bacterial cause of this life-threatening condition for the fetus.

Staphylococcal infections are contagious and can be transmitted from person to person. Since pus from infected wounds may contain the bacteria, proper hygiene and hand washing is required when caring for Staph-infected wounds.

Staphylococcal food poisoning is an illness of the bowels that causes nausea, vomiting, diarrhea, and dehydration. It is caused by eating foods contaminated with toxins produced by Staphylococcus aureus rather than a true infection with the bacteria. Symptoms usually develop within one to six hours after eating contaminated food. The illness usually lasts for one to three days and resolves on its own. Patients with this illness are not contagious since toxins are not transmitted from one person to another.

Toxic shock syndrome is an illness caused by toxins secreted by Staph aureus bacteria growing under conditions in which there is little or no oxygen. Toxic shock syndrome is characterized by the sudden onset of high fever, vomiting, diarrhea, and muscle aches, followed by low blood pressure (hypotension), which can lead to shock and death. There may be a rash resembling sunburn, with peeling of skin. Toxic shock syndrome was originally described and still occurs especially in menstruating women using tampons.