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What Is Staphylococcus?
Staphylococcus is a group of bacteria that can cause a multitude 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. 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 body locations) of 25%-30% of healthy adults. 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. People who inject drugs or medications, or have skin injuries or disorders, intravenous catheters, or surgical incisions, and those with a weakened immune system all have an increased risk of developing Staph infections.
What Are the Signs and Symptoms of a Staph Infection?
Staphylococcal disease of the skin usually results in a localized collection of pus, known as an abscess, boil, or furuncle. The affected area may be red, swollen, and painful. Drainage or pus is common. When Staph is in the blood (known as bacteremia or sepsis) it can cause high fevers, chills, and low blood pressure.
What Types of Diseases Are Caused by Staph?
Skin infections 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 connective tissue under the skin, leading to swelling and redness of the area). 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 (known as bacteremia or sepsis), a number of serious infections can occur such as staphylococcal pneumonia, infection of the heart valves (endocarditis, which can lead to heart failure), and osteomyelitis (severe inflammation of the bones). 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%.
What Is Antibiotic-Resistant Staph aureus?
Methicillin-resistant Staphylococcus aureus, known as MRSA, is a type of Staphylococcus aureus that is resistant to the antibiotic methicillin and other drugs in the same class, including penicillin, amoxicillin, and oxacillin. MRSA is one example of a so-called "superbug," an informal term used to describe a strain of bacteria that has become resistant to the antibiotics usually used to treat it. MRSA first appeared in patients in hospitals and other health facilities, especially among the elderly, the very sick, and those with an open wound (such as a bedsore) or catheter in the body (health-care-associated MRSA or HA-MRSA). MRSA has since been found to cause illness in the community outside of hospitals and other health facilities and in this case is known as community-associated MRSA (CA-MRSA). MRSA in the community is associated with recent antibiotic use, sharing contaminated items, having active skin diseases or injuries, poor hygiene, and living in crowded settings.
What Are Complications of Staph Infections?
Scalded skin syndrome is a potentially serious side effect of infection with Staph bacteria that produce a specific protein which loosens the "cement" holding the various layers of the skin together. This allows blister formation and sloughing of the top layer of skin. If it occurs over large body regions, it can be deadly, similar to a large surface area of the body having been burned. It is necessary to treat scalded skin syndrome with intravenous antibiotics and to protect the skin from dehydration if large areas peel off. The disease occurs predominantly in children but can occur in anyone. It is known formally as staphylococcal scalded skin syndrome.
What Is Staph Food Poisoning?
Staph food poisoning is a type of food poisoning caused by infection with the Staphylococcus aureus (S. aureus) bacterium. The bacteria multiply in foods and produce a toxin even at refrigerator temperatures. The toxins may be present in dangerous amounts in foods that have no signs of spoilage, such as a bad smell. Most people get Staph poisoning by eating contaminated food. The most common reason for contamination is that the food has not been kept hot enough [140 F or above] or cold enough [40 F or below]. Foods that are associated with Staph food poisoning include meats, poultry and egg products, salads (egg, tuna, chicken, potato, macaroni), bakery products (cream filled), sandwich fillings, and milk and dairy products.
How Are Staph Infections Diagnosed?
In cases of minor skin infections, staphylococcal infections are commonly diagnosed by their appearance without the need for laboratory testing. More serious staphylococcal infections such as infection of the bloodstream, pneumonia, and endocarditis require culturing of samples of blood or infected fluids. A sample of the infected wound (either a small biopsy of skin or pus taken with a swab) or of the blood must be obtained to grow the bacteria in the microbiology laboratory. Once the Staph is growing, the organism is tested to determine which antibiotics will be effective for treating the infection. A culture of skin lesions is especially useful in recurrent or persistent cases of skin infection, in cases of antibiotic failure, and in cases that present with advanced or aggressive infections.
What Does Staphylococcus aureus Bacteria Look Like?
This highly magnified electron micrograph depicted numbers of Staphylococcus aureus bacteria, which were found on the luminal (inside) surface of an indwelling catheter. Of importance is the sticky-looking substance woven between the round cocci bacteria, which is composed of polysaccharides and is known as “biofilm.” This biofilm has been found to protect the bacteria that secrete the substance from attacks by antimicrobial agents such as antibiotics, resulting in methicillin-resistant Staphylococcus aureus, or MRSA.
How Are Staph Infections Treated?
Minor skin infections are usually treated with an antibiotic ointment such as a nonprescription triple-antibiotic mixture. In some cases, oral antibiotics may be given for skin infections. Additionally, if abscesses are present, they are surgically drained. More serious and life-threatening infections are treated with intravenous antibiotics. The choice of antibiotic depends on the susceptibility of the particular staphylococcal strain as determined by culture results in the laboratory. Skin lesions may also be treated by drainage of the lesion under sterile conditions. Some Staph strains, such as MRSA, are resistant to many antibiotics.
Can Staph Infections Be Prevented?
No vaccine is available against Staphylococcus aureus. Since the bacteria are so widespread and cause so many different diseases, prevention of Staph infections requires attention to the risk factors that may increase the likelihood of getting a particular type of Staph infection. The following slides show recommended steps in preventing the spread of Staph and MRSA infections.
Staph Prevention Tip #1
Keep infections, particularly those that continue to produce pus or to drain material, covered with clean, dry bandages. Follow your health-care provider's instructions on proper care of the wound. Pus from infected wounds can contain MRSA and spread the bacteria to others.
Staph Prevention Tip #2
Prevention of Staph infections can be aided by proper hygiene when caring for skin wounds. Careful hand washing, avoiding close skin contact with possible infected individuals, and proper hygienic care of skin scrapes, cuts, and wounds can all reduce the likelihood of skin infections due to Staph, including community-acquired MRSA. Advise your family and other close contacts to wash their hands frequently with soap and warm water, especially if they change your bandages or touch the infected wound or potentially infectious materials.
Staph Prevention Tip #3
Avoid sharing personal items (for example, towels, washcloth, razor, clothing, or uniforms) that may have had contact with the infected wound and potentially infectious material. Wash linens and clothes that become soiled with hot water and laundry detergent. Drying clothes in a hot dryer, rather than air-drying, also helps kill bacteria in clothes.
Staph Prevention Tip #4
Careful attention to food-handling and food-preparation practices can decrease the risk of staphylococcal food poisoning:
- Wash hands and under fingernails vigorously with soap and water before handling and preparing food.
- Do not prepare food if you have a nose or eye infection.
- Do not prepare or serve food for others if you have wounds or skin infections on your hands or wrists.
- Keep kitchens and food-serving areas clean and sanitized.
- If food is to be stored longer than two hours, keep hot foods hot (over 140° F) and cold foods cold (40° F or under).
- Store cooked food in a wide, shallow container and refrigerate as soon as possible.
Staph Prevention Tip #5
It is possible for menstruating women to reduce the risk of toxic shock syndrome (a rare, life-threatening illness that is caused by toxins secreted by Staph bacteria) by frequently changing tampons (at least every four to eight hours), using low-absorbency tampons, and alternating sanitary pad and tampon use. Toxic shock has been associated with tampon use, particularly when tampons are not changed frequently.
Staph Prevention Tip #6
Tell any health-care providers who treat you that you have a Staph or MRSA skin infection.
Staph Infection Prognosis
If a Staph infection is treated early with appropriate antibiotics and, if necessary, surgical drainage, the patient's prognosis is excellent. However, the U.S. National Institutes of Health (NIH) warns that the outcome of a MRSA infection varies both with the severity of the infection and the general condition of the person who has the infection. MRSA pneumonia and blood poisoning (sepsis) have high death rates; the calculated death rate of invasive MRSA is about 20%. HA-MRSA (hospital-acquired MRSA) infections are a growing problem; it is reported that about 19,000 deaths per year in the U.S. are due to MRSA, which is more deaths than HIV causes per year. Fortunately, people who have good general health and have mild CA-MRSA (community-acquired MRSA) that is appropriately treated recover in almost every case.
Staph Infection At A Glance
- Staphylococcus is group of bacteria that can cause a multitude of diseases.
- Staph infections may cause disease due to direct infection or due to the production of toxins by the bacteria.
- Boils, impetigo, food poisoning, cellulitis, and toxic shock syndrome are all examples of diseases that may be caused by Staphylococcus.
- Methicillin-resistant Staphylococcus aureus, known as MRSA, is a type of Staphylococcus aureus that is resistant to the antibiotic methicillin and other drugs in this class.
- Staph infections are treated with topical, oral, or intravenous antibiotics, depending upon the type of infection.
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