MRSA skin infection
- Reviewed by Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
What is it?
Many types of bacteria can cause skin infections. Most cases are caused by Staphylococcus aureus ("staph") or Streptococcus pyogenes ("strep"). Strep infections still respond well to standard antibiotics. However, that is not true for all staph infections.
Over the last few decades, it has become more common for a certain strain of drug-resistant staph bacteria to cause skin infections. Originally, these resistant staph infections were seen mostly in hospitals. But now they have spread into the general community. This strain of bacteria is named community-acquired methicillin-resistant Staphylococcus aureus, or "community-acquired MRSA."
Skin infections include cellulitis, abscesses (boils), or a combination of the two. MRSA bacteria can cause skin infections that don't look any different from those caused by common staph and strep. However, MRSA skin infections are more likely to show blisters or develop abscesses.
Skin infections occur when strep or staph bacteria break through the skin's protective outer layer, typically at the site of an injury, such as a cut, puncture, sore, burn, or bite. Once beneath the skin surface, the bacteria multiply and make chemicals that cause inflammation in the skin.
Cellulitis most often occurs on the legs and feet. However, it can develop on any part of the body, including the trunk, arms, and face. It often develops where there is edema (swelling), poor blood flow, or a skin rash that creates breaks in the skin, such as a fungal infection between the toes (athlete's foot).
Symptoms
In cellulitis, the affected skin feels warm and is usually red, swollen, and painful. The redness can be slight or can stand out dramatically compared to the surrounding skin. The area of warmth can be felt with the back of the hand, especially when compared to surrounding skin. There may be a spreading network of red streaks in the skin, caused by infection in the vessels that carry lymph (tissue fluid), as well as enlarged lymph nodes (swollen glands) near the area of infection.
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If you have blisters or pus on the surface of your skin rash, the cellulitis is more likely to be caused by MRSA.
Fever and a general feeling of sickness (malaise) often accompany cellulitis. Severe infections can cause abnormally low blood pressure if bacteria get into the bloodstream.
Diagnosis
Many people who develop a skin infection have no other medical problems and no obvious injury or skin damage that allowed the infection to occur. This is also true for people with a MRSA skin infection. However, people in certain groups have a much higher risk than others that their skin infection is caused by MRSA:
- people who have been in a hospital or nursing home
- people with immune system problems or diabetes
- people who are already taking an antibiotic.
Your doctor can usually diagnose whether you have cellulitis, a boil, or a carbuncle based on your recent medical history, your symptoms, and a physical examination. Your doctor may also recommend tests to look for other conditions that could indicate something different or a deeper, more serious infection.
In most cases, your doctor will not be able to tell you which specific bacteria type has caused your skin infection. For simple boils, drainage is often sufficient without the need to take an antibiotic. Cellulitis, carbuncles, and large boils usually require treatment with antibiotics.
MRSA skin infections look like infections caused by other types of bacteria. If your doctor is concerned about MRSA, he or she will choose an antibiotic that is recommended for MRSA skin infections.
Your doctor may perform a culture of the pus in a boil or carbuncle to determine if it contains MRSA. Studies have shown that culture of the skin in people with cellulitis is not useful. Your treatment can be adjusted if you are not improving.
Expected duration
How long a skin infection lasts depends on the extent of the infection, the bacteria that caused the infection, and your general health. Without proper antibiotic treatment, some skin infections can cause serious complications within a few days, even in otherwise healthy people.
Prevention
To help prevent MRSA skin infections:
- Prevent skin injury. Wear protective gloves while gardening and working outdoors. Wear long sleeves and trousers while hiking. Avoid going barefoot outdoors. Wear protective padding on elbows and knees while skating.
- Treat minor skin wounds and bumps in hair follicles promptly. Gently wipe away dirt, wash thoroughly with antibacterial soap and water, apply antiseptic ointment, and cover with a clean bandage. At the earliest sign of irritation or a bump at a hair follicle, use warm compresses to open up the blocked pore and drain any early infection.
- Seek medical attention. Medical attention is needed for all deep puncture wounds and animal bites and for all deep wounds involving a joint, hand, or foot.
Treatment
Cellulitis is treated with antibiotics. An abscess usually needs to be treated with incision and drainage (I & D). Your doctor will choose a specific antibiotic depending on the site of your skin infection and how likely it is that MRSA caused it. Most cases of cellulitis improve quickly once you start taking antibiotics. Once an abscess is drained, the person will quickly begin to feel better. Your doctor may prescribe a course of antibiotics after the I & D.
If you have mild cellulitis, you can usually treat it at home with antibiotics taken by mouth. The oral antibiotics used most often are trimethoprim-sulfamethoxazole, doxycycline or clindamycin. However, keep in touch with your doctor to be sure that the infection is improving as expected. It also helps to apply warm compresses, such as a warm, moist washcloth, and elevate the infected area.
If you have severe cellulitis, you may need to be treated in the hospital with antibiotics given intravenously (into a vein), usually IV vancomycin.
When to call a professional
Call your doctor whenever a skin injury becomes red, warm, swollen, or tender. Call your doctor promptly if you get a deep puncture wound, especially on a hand or foot, or if you are bitten by an animal or human.
Prognosis
In most cases, skin infections begin to improve within 24 to 48 hours after starting appropriate treatment. Very rarely, the infection may involve tissues below the skin. These deeper infections can be extremely serious and require intensive in-hospital treatment.
Additional info
National Center for Infectious Diseases
https://www.cdc.gov/ddid/centers.html
About the Reviewer
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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