Staph infection: Causes, symptoms and treatment

Many people have staph bacteria in their nose or on their skin, such as on the armpit, groin and other areas, but it usually doesn’t lead to a staph infection. But when staph (Staphylococcus aureus or S. Aureus) bacteria enters your body or skin through a cut, scrape or abrasion, mild infections such as abscesses and cellulitis can develop, as can more serious infections such as pneumonia and bloodstream infections.

The most recent data available from the Centers for Disease Control and Prevention (CDC) show that over 119,000 people suffered from bloodstream staph infections, and nearly 20,000 of those people died.

Certain people have a higher risk for developing a staph infection, including:

• Individuals who have come in contact with a person with staph
• People who have been in a healthcare facility
• People who have had surgery or those who have had an invasive medical device such as an IV inserted through their skin
• Individuals who have injected drugs such as opioids.
• People with a weakened immune system, such as those with HIV/AIDS or undergoing chemotherapy treatment
• Individuals with certain chronic conditions, such as diabetes, cancer, vascular disease, eczema and lung disease, may also be at a greater risk

Staphylococcus is a group of bacteria consisting of over 30 different types of bacteria. The type called Staphylococcus aureus causes most infections, with the most common being skin infections. Staph bacteria can also cause bone infections, food poisoning, toxic shock syndrome, endocarditis (an infection of the endocardium, the inner lining of the heart chambers and valves), and pneumonia. If these infections get into the bloodstream, they can lead to sepsis, a very serious immune response to infection that can be life-threatening.

A specific type of staph bacteria, methicillin-resistant staphylococcus aureus (MRSA), is especially dangerous and has been labeled a "superbug." Antibiotics have been prescribed for colds, the flu, and other viral infections that actually do not resolve with these medications. Due to this overuse of antibiotics, these staph bacteria have adapted, becoming resistant to antibiotic treatment, such as with penicillins (e.g., amoxicillin, methicillin and oxacillin). This makes MRSA infections difficult to treat and may allow the infections to spread and sometimes become life-threatening.

Those at a higher risk for a serious MRSA infection are people who have been in a hospital setting, especially an intensive care unit (ICU) or a dialysis center, as these are usually associated with invasive procedures or the use of devices such as intravenous tubing or artificial joints. The CDC reports that approximately 5% of patients in U.S. hospitals carry MRSA in their nose or on their skin. When MRSA infections occur in these types of settings, they are referred to as healthcare-associated MRSA (HA-MRSA).

Another type of MRSA infection occurs in the wider community among healthy people. This type, called community-associated MRSA (CA-MRSA), often begins as a painful skin boil. It's usually spread by skin-to-skin contact, so the risk of acquiring CA-MRSA increases with activities or places that involve crowding, close skin contact and sharing of equipment or supplies. For example, athletes (due to the heavy skin-to-skin contact with cuts and abrasions), daycare and school students, and military personnel may be at a higher risk.

About one-third of the general population carries staph bacteria on their skin or in their nose, but this doesn't mean they have a staph infection. However, if the bacteria enters the body through a break, cut or abrasion in the skin, this is when the infection can occur. Staph, including MRSA infections, are transmitted by physical skin contact in healthcare or community settings when touching an infected person. It can also be transmitted by touching clothing, a towel, door handles, remote control devices, smartphones or athletic equipment that carries the bacteria. When food is prepared improperly by someone with a staph infection, this can also transmit the bacteria.

Once staph bacteria has caused an infection to develop inside your body, the amount of time it takes for symptoms to occur varies. Symptoms can appear anywhere from one to 10 days. For example, staph bacteria is one of the most common causes of food poisoning, and the toxins formed by the bacteria can cause symptoms to occur very quickly, often within hours of eating a contaminated food.

Staph infections can range from minor skin problems to life-threatening illness. The signs and symptoms vary greatly, depending on the location and type of the infection:

• Skin infections can look like pimples or boils that may become red, swollen and painful. These may also develop pus or other drainage and can sometimes turn into impetigo, which is a rash that has large blisters with a honey-colored crust, or cellulitis, which is characterized by swollen, red skin that feels hot. A common complaint by patients with a staph infection is feeling like they have a spider bite.
• Bone infections can cause pain, swelling, warmth and redness in the affected area. Chills and a fever may also develop.
• Endocarditis causes some flu-like symptoms, such as fever, chills and fatigue. It can also cause symptoms such as rapid heartbeat, shortness of breath and fluid buildup in the legs and arms.
• Food poisoning can cause nausea, vomiting, diarrhea and fever. The loss of fluids can also lead to dehydration.
• Pneumonia can cause symptoms such as a high fever, chills and cough that doesn’t resolve. Chest pain and shortness of breath can also occur.
• Toxic shock syndrome (TSS) is a life-threatening condition caused by toxins produced by S. Aureus and is mainly linked to extended use of tampons (tampons should be changed every four to eight hours). TSS typically causes high fever, sudden low blood pressure, vomiting, diarrhea and confusion.

MRSA infections can infect the bloodstream, lungs, heart, bones, joints or any area where you recently had surgery.

If you think you have a staph infection, do not pick at or pop the sore. Cover the affected skin with clean, dry bandages, wash your hands often, and contact a healthcare provider before it develops into a more serious infection, especially if you have a fever.

The healthcare provider will review your symptoms, complete a physical exam, and drain the infected lesion if necessary. They'll culture the wound drainage, blood, urine, skin or nasal secretions as needed to test for the presence of staph bacteria. The provider may also order imaging tests, depending on your symptoms and exam results. For example, an echocardiogram may be ordered to determine if the infection has affected your heart.

Your healthcare provider will decide if you need antibiotics and will determine which may be the most effective based on the culture results if cultures were taken. You may be prescribed antibiotic creams or ointments, or you may need to take an antibiotic by mouth or intravenously (through an IV). The preferred treatment for MRSA is vancomycin every 8–12 hours by mouth or by IV, or daptomycin by IV once a day. If culture results show the bacteria is methicillin-susceptible staph aureus (MSSA), antibiotic treatment can be changed to nafcillin, oxacillin or cefazolin by mouth. In some cases, treatment with medications either by mouth or IV may last 14 days but may start resolving the infection, showing a staph-negative blood culture in 72 hours. People with a more serious infection may need IV treatment for more than two weeks.

If the infection progresses and systemic symptoms, such as septicemia, blood poisoning or surgery site infections, develop, get worse or do not improve within 48 hours, your healthcare provider may change your treatment plan, and you may be referred to an infectious disease specialist. You may also need surgery to drain deep, painful abscesses. If your infection involves an implanted medical device, such as a cardiac pacemaker or artificial joint, the device may need to be removed.

If caring for your infected site at home, make sure to keep the wound clean and cover it with clean, dry bandages to absorb any wound drainage. Discard any used dressings quickly. Make sure you wash your hands after caring for the wound to prevent spreading the infection to others. Whenever possible, wear clothes that cover your bandages and wound. It is also important to avoid contact sports as well as public gyms, saunas, hot tubs and swimming pools until the wound has healed.

It's important to disinfect your home to keep the infection from spreading to others. Any cleaning product with “disinfectant” on the label that can be purchased at the grocery store or pharmacy is sufficient. You can also make your own bleach solution. Clean areas of your home that are frequently used, such as bathrooms, countertops, light switches, doorknobs, phones, etc. When doing laundry, wear disposable gloves, especially when handling laundry soiled with drainage from a sore or wound. Also, hold dirty laundry away from your body and clothes to avoid getting the bacteria on your clothes.

Here are some ways to prevent the spread of staph infections:

• Wash your hands carefully with soap and running water, scrubbing for at least 20 seconds. If soap and water are not available, use a hand sanitizer with at least 60% alcohol.
• Don't share personal products, such as towels, sheets, clothing, razors and athletic equipment.
• Sanitize linens if you have a sore or cut. Wash towels and bedding using the hottest water setting in a washing machine and dry them using the hottest setting in the dryer.
• Clean abrasions and cuts and keep them covered with clean, dry bandages until healed.
• Shower with soap after participating in sports. Do not share your towel with others.
• Do not prepare food for others if you have a staph infection.
• Stay away from illicit drugs. People who use intravenous drugs have an increased risk of MRSA, hepatitis C and HIV.

If you plan to visit someone with MRSA in the hospital, know that both visitors and healthcare workers will be required to wear protective garments and follow strict hand-washing procedures to keep the infection from spreading.

Clinically reviewed and updated by Rebeca Thomas, BSN, RN, CPHQ, September 2022.