Often referred to as a superbug, MRSA infection may begin as a skin sore, pimple, or boil, before becoming serious, potentially harmful, and sometimes fatal.
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Fast facts on MRSA
Here are some key facts about MRSA. More detail and supporting information is in the main article.
- MRSA is a form of bacterial infection that is resistant to numerous antibiotics.
- "Staphylococcus aureus" refers to a bacterium that commonly resides inside the nose and on human skin.
- Around one in three people carry staph in their nose, usually without any illness. Two in 100 people carry MRSA.
- The majority of invasive MRSA infections are contracted with healthcare settings.
- Germ-killing soaps and ointments used in intensive care units have been found to significantly reduce MRSA cases.
MRSA: Meaning and definition
"Methicillin" is an antibiotic related to penicillin; it was once effective against staphylococci (staph), a type of bacteria. Staph bacteria have since developed a resistance to penicillin-related antibiotics, including methicillin - these resistant bacteria are called methicillin-resistant staphylococcus aureus, or MRSA.
MRSA is a form of bacterial infection that is resistant to numerous antibiotics.
In the United States, staph bacteria are one of the most common causes of skin infections, including:
Staph bacteria can cause infections, and the resulting conditions range from mild to life threatening. These conditions include:
- septicemia (blood poisoning)
- pneumonia (lung infection)
- osteomyelitis (bone infection)
- endocarditis (heart valve infection)
- urinary tract infection (e.g. bladder infection)
- septic bursitis (small fluid-filled sacs under the skin)
Around 94,360 invasive MRSA infections are diagnosed annually in the U.S., with 18,650 associated deaths. MRSA infections are typically classified as healthcare-associated or community-associated; approximately 86 percent of all invasive MRSA infections are healthcare-associated.
MRSA infection symptoms
MRSA symptoms depend on what area of the body is infected. Although many people carry MRSA bacteria in their mucosa (for instance, the membrane on the inside of the nose), they may never display any symptoms of active infection.
Staph skin infections, including MRSA, appear as a bump or sore area of the skin that could be mistaken for an insect bite. The infected area might be:
Symptoms of a serious MRSA infection in the blood or deep tissues include:
- fever of 100.4 °F or higher
- aches and pains of the muscles
- swelling and tenderness in the affected body part
- chest pains
- breathlessness (dyspnea)
- wounds that do not heal
Ultimately, MRSA is caused by bacterium strains that have acquired a resistance to particular antibiotics.
MRSA is contagious
MRSA can spread from person-to-person (skin-to-skin contact) and from person-to-object-to-person when an individual has active MRSA or is colonized by the bacteria.
Skin-to-skin contact with someone carrying MRSA is not necessary for infection to spread. MRSA bacteria are also able to survive for extensive periods on surfaces and objects including door handles, floors, sinks, taps, cleaning equipment, and fabric.
MRSA surface longevity
MRSA bacteria have the aptitude to survive for extensive periods on surfaces and objects in hospitals including door handles, floors, sinks, taps, cleaning equipment and fabric.
One study to determine the survival of resistant staph on common hospital surfaces looked at staph survival on five materials commonly found in a hospital:
- 100 percent smooth cotton (clothing)
- 100 percent cotton terry (towels and wash cloths)
- 60 percent cotton, 40 percent polyester blend (scrub suits, lab coats and clothing)
- 100 percent polyester (privacy drapes, curtains, and clothing)
- 100 percent polypropylene plastic (splash aprons)
Swatches of fabric were injected with 10,000-100,000 colony-forming units (CFU) of the microorganism and observed daily. They found that S. aureus survived on the materials for the following number of days:
- cotton - 4-21 days
- terry - 2-14 days
- polyester blend - 1-3 days
- polyester - 1-40 days
- polypropylene - 40-greater than 51
These results demonstrate the need for thorough contact control and meticulous disinfection procedures to limit spread of bacteria.
MRSA frequently causes illness in people with a compromised immune system who interact with or reside in hospitals and healthcare facilities.
This is referred to as healthcare-associated MRSA (or hospital-acquired MRSA) and often occurs for one of the following reasons:
- A break in the skin barrier - such as a surgical wound, burn, catheter, or intravenous line that allows bacteria to enter the body.
- Older age - comorbidities or multiple complex health issues, and weakened immune systems due to a specific health condition, or the use of medications that lower immune function.
- Large numbers of people - the simple fact that hospitals and healthcare facilities are visited by many different people provides an environment for bacteria to easily spread.
Those with a weakened immune system can include:
- patients in hospital for a long period of time
- patients on kidney dialysis
- patients receiving cancer treatment or specific medications that affect immune function
- those who inject illegal drugs
- individuals who have had surgery within a year of being back in hospital
According to the Centers for Disease Control and Prevention (CDC) study, invasive healthcare-associated MRSA infections declined 54 percent between 2005 and 2011, with 30,800 fewer severe MRSA infections and 9,000 fewer deaths.
A similar study conducted by the National Healthcare Safety Network (NHSN) found that rates of health care-associated MRSA bloodstream infections fell nearly 50 percent from 1997-2007.
The average age of a person with healthcare-associated MRSA was 68.
Who is at risk of MRSA
People most at risk of developing healthcare-associated MRSA in the hospital include those that have:
- weakened immune systems
- open wounds
- a catheter or intravenous drip inserted
- burns or cuts to the skin surface
- severe skin conditions
- had surgery
- frequent antibiotics as part of their treatment
Regular skin-to-skin interaction in sports such as rugby, ice hockey, soccer, or basketball increase the risk of developing community-associated MRSA.
Community-associated MRSA is contracted outside of a hospital setting; it is less common than healthcare-associated MRSA. Factors that cause increased risk of developing community-associated MRSA include:
- living in an environment with a lot of people; military bases, jail, on-campus housing
- regular skin-to-skin interaction for example in contact or collision sports such as rugby, ice hockey, soccer, and basketball
- cuts or grazes to the skin or regular injection of drugs
- contaminated surfaces
- unhygienic facilities or lack of personal hygiene
- previous antibiotics use
The CDC reports that 14 percent of people with MRSA infections contracted them outside of healthcare setting.
The average age of a person with community-associated MRSA was 23.
The 5 Cs can be used to remember what factors make it easier for MRSA to be transmitted:
- contact (skin-to-skin)
- compromised skin (open wounds)
- contaminated (items and surfaces)
- cleanliness (lack of)
Treatment and prevention of MRSA
If MRSA is diagnosed, treatment will vary depending on the following factors:
- type of infection
- location of infection
- severity of symptoms
- antibiotics to which the strain of MRSA responds
Management of MRSA infections may include:
- pus drainage from lesion
- culture and susceptibility testing of drained material
- wound care and hygiene
- antimicrobial therapy (in cases of possible cellulitis without abscess)
Medication options for MRSA skin and soft tissue infections may include:
- tetracycline drugs - doxycycline and minocycline
- trimethoprim and sulfamethoxazole
Healthcare-associated MRSA infection prevention
Actions such as regular hand washing can reduce risk of community-associated MRSA outside of hospitals.
Doctors, nurses, and other healthcare providers have the following measures in place to prevent MRSA infections:
- Hand cleanliness - using soap and water or alcohol-based hand rub between caring for patients.
- Hospital rooms and equipment - ensuring thorough cleaning.
- Keeping patients with MRSA separate from other patients - either in a single room or shared with another person who has MRSA.
- Healthcare providers clothing - wearing gloves and gown over clothing while caring for MRSA patients.
- Visitor clothing - wearing of gloves and gowns.
- Disposal and cleanliness - visitors and hospital providers removing and disposing of gowns and gloves after exiting the patient's room and washing hands thoroughly.
- Access to common areas - patients with MRSA will be asked to limit movement around the hospital, avoid gift shops or cafeterias and stay in their rooms.
- MRSA swabbing - to identify if some non-MRSA patients have MRSA on their skin.
Community-associated MRSA infection prevention
The following actions can reduce risk of community-associated MRSA outside of hospitals:
- regular hand-washing
- keeping fingernails short
- avoiding sharing products such as soaps, lotions, creams, and cosmetics with others
- avoiding sharing unwashed towels
- avoiding sharing personal items such as razors, nail files, toothbrushes, combs, or hairbrushes
MRSA tests and diagnosis
Healthy people are sometimes tested to identify if they have MRSA on their skin before being admitted to the hospital. The test involves swabbing the inside the patient's nostrils or skin.
If the person is found to be colonized with MRSA, removal (decolonization) of the bacteria is possible by using:
- antibacterial body wash or powder for the skin (chlorhexidine baths)
- cream for inside the nose (intranasal mupirocin)
- antibacterial shampoo for the scalp (chlorhexidine soap shower/bath procedure)
Germ-killing soaps and ointments used in intensive care units (ICU) have been found to reduce cases of MRSA by 40 percent.