What Is Staphylococcus Aureus?


About 25 to 30 percent of people carry Staphylococcus aureus, a type of bacterium commonly called “staph,” without developing an infection. However, if you eat food that's contaminated by some strain of staph, you will be one of the many people who contract food-borne illnesses from these bacteria. Additionally, staph is one of the most widespread causes of skin infection in the United States.

Carriage and Transmission

Staph bacteria can live in air, dust and sewage, and is transported mainly by people and animals. Staph can also live in food, particularly food that hasn't been kept hot or cold enough to stop bacteria growing and reproducing. While many healthy individuals carry Staphylococcus aureus, it's predominant among people who handle food and food equipment. Generally, those who work in hospitals or among sick people also face a higher chance of contact with staph, usually via contaminated hands. MedicineNet.com cites a study describing three patterns of carriage. Some people constantly carry a strain of staph; others carry different strains at different times; while a third group never carries staph at all. More children than adults belong to the first group, which always carries the bacteria. You can project yourself against staph infection in three simple ways: storing food properly, washing hands frequently and keeping cuts clean and covered.

Methicillin-Resistant Staphylococcus Aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a strain that's resistant to the usual antibiotics used to treat staph infection, making MRSA infections more difficult to treat. MRSA usually infects the skin. This generally mild infection can be treated with a different set of antibiotics and attentive skin care. However, because fewer antibiotics are effective against MRSA, it may become more serious given the opportunity to infect other areas, such as bones. Rarely, MRSA may cause pneumonia, most commonly among children who have the flu and therefore compromised immunity. While staph colonizes much of the population, MRSA colonizes only about 1 percent of people. MRSA first appeared in health facilities, particularly among the elderly, the very sick or those with open wounds (Heathcare-associated MRSA or HA-MRSA). It now affects those who don’t spend time in health facilities, usually related to crowded lifestyles, substandard hygiene or sharing tainted objects (Community-associated MRSA or CA-MRSA). The U.S. Centers for Disease Control and Prevention estimate that CA-MRSA accounts for about 12 percent of MRSA infections.

Staphylococcus Aureus on the Skin

If your skin is broken, staph bacteria on your skin can enter the wound and cause an infection, usually minor. This generally remains a soft-tissue infection that goes away with simple antimicrobial treatment, but infections sometimes become serious. For instance, staph entering a surgical wound could infect the bloodstream. One version of staph infection of the skin is characterized by the formation of an abscess, or a bump that's usually filled with pus. The area around the abscess will be swollen, red, warm and painful. A slightly deeper infection called cellulitis may occur, characterized by redness, pain, and swelling. Cellulitis affects deeper layers of skin, usually on limbs but possibly anywhere. Generally, staph infects these underlying layers only through scrapes, cuts or other injuries. Milder skin infections often heal without any treatment, usually within a few weeks. However, the infection may need to be drained or require antibiotics.

Staphylococcus Aureus in Food

The hardy Staphylococcus aureus bacteria can survive temperatures as high as 50 degrees Celsius, high salt concentrations, and dry environments. Staph thrives at temperatures close to normal body temperature (37 degrees Celsius). The bacteria themselves don't cause food-borne illness, but rather the toxin they produce, which is harder to destroy and requires even higher temperatures. To prevent formation of this toxin, store food at about 60 degrees Celsius. Cool cooked food and refrigerate it quickly. Foods touched by many people as they're prepared, such as potato, tuna or egg salads, or foods that are left warm for a while after preparation, such as chili or soup, are susceptible to becoming “poisonous.” Symptoms generally have a rapid onset, including nausea, vomiting and cramping abdominal pain. More serious cases may involve headache, muscle cramps and fluctuations in blood pressure. Food poisoning from staph toxin isn't contagious, and victims generally recover within a few days.

More Serious Infections Caused by Staphylococcus Aureus

Staph bacteria in the bloodstream, called sepsis or bacteremia, may cause shock and the collapse of the circulatory system, ultimately resulting in death. People with severe, widespread burns face a higher risk of developing Staphylococcus sepsis. From the bloodstream, bacteria may spread to other organs. If the lungs are infected, pneumonia may occur. Additionally, abscesses might form within the lungs. If staph infects the heart, heart failure is possible. If staph spreads to the bones, they may become severely inflamed.

Other Complications of Staphyococcus Aureus

One rare complication of Staphylococcus aureus is known as staphylococcal scalded skin syndrome (SSSS). More common in children than adults, this potentially serious side effect occurs when staph bacteria produce an exotoxin that causes the various layers of skin to detach from each other. Widespread, red, fluid-filled blisters form that can be easily broken. Once they rupture, the skin looks as if it has been burned or scalded, hence the name. If it affects a large enough area, SSSS can be extremely serious, even deadly. Treatment requires hospitalization for intravenous administration of antibiotics. After a few days, the patient can usually be discharged and continue treatment with oral antibiotics. Another complication occurs in breastfeeding women. Their breasts may become inflamed or an abscess may form, which can release bacteria into the milk. Finally, toxic shock syndrome (TSS) can be caused if the toxins produced by staph bacteria grow in an area with little or no oxygen. TSS usually occurs in menstruating women using tampons and is characterized by the acute onset of a very high fever, vomiting, diarrhea, and muscle pain. Very low blood pressure comes next, which may lead to shock and even death.

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