MRSA, (methicillin-resistant staphylococcus aureus), is a form of bacterial infection that is resistant to numerous antibiotics including methicillin, amoxicillin, penicillin and oxacillin, thus making it challenging to treat the infection successfully.1
Often referred to as a superbug, MRSA infection may commence as a minor skin sore, pimple or boil, before becoming serious, potentially harmful and sometimes fatal.
Contents of this article:
What is MRSA?
Causes of MRSA
Symptoms of MRSA
What is antibiotic resistance?
Tests and diagnosis
Treatment and prevention of MRSA
You will also see introductions at the end of some sections to any recent developments on MRSA that have been covered by MNT’s news stories. Also look out for links to information about related conditions.
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.
MRSA infection can begin as a minor skin sore or pimple and become potentially harmful.
“Methicillin” represents the antibiotic that was once effective against staphylococci (staph).
“Staphylococcus aureus” refers to a bacterium that commonly resides inside the nose and human skin.
Around one in three (33%) people carry staph in their nose, usually without any illness. Two in 100 people carry MRSA.
MRSA can be divided between health care associated MRSA and community associated MRSA.
Annually, there are around 94,360 invasive MRSA infections diagnosed in the US, with 18,650 associated deaths.
It is estimated that 49-65% of health care associated S. aureus infections are caused by methicillin-resistant strains.
Invasive health care associated MRSA infections declined by 54% between 2005 and 2011.
Approximately 86% of all invasive MRSA infections are contracted with health care settings.
Germ-killing soaps and ointments used in intensive care units have been found to reduce MRSA cases by 40%.
What is MRSA?
“Methicillin” represents the semisynthetic penicillin-related antibiotic once effective against staphylococci (staph).2 Staph bacteria have developed a resistance to penicillin-related antibiotics, including methicillin – these resistant bacteria are called methicillin-resistant staphylococcus aureus, or MRSA.
“Staphylococcus aureus” (S. aureus) refers to an often harmful bacterium, commonly found in the nose and skin of humans.3 In the US, staph bacteria are one of the most common causes of skin infections. Although 33% of the population is colonized with staph (bacteria is present but not causing infection), around 2% of the population is colonized with MRSA.10
MRSA, full name methicillin-resistant staphylococcus aureus, is a form of bacterial infection that is resistant to numerous antibiotics including methicillin, amoxicillin, penicillin and oxacillin.
The bacterium that can cause staph skin infections can divide every half-hour in optimum conditions. Theorectically, a single cell can form a colony of more than a million cells in 10 hours.5
S. aureus can cause skin infections including:
Staph bacteria can also enter the body, and invade the bloodstream through broken or damaged skin or during medical procedures, and can cause infections and resulting conditions that range from mild to severely life-threatening. These conditions may include:
Septicemia (blood poisoning)
Pneumonia (lung infection)
Osteomyelitis (bone infection)
Endocarditis (heart valve infection)
Urinary tract infection (eg. bladder infection)
Septic bursitis (small fluid-filled sacs under the skin).
Around 94,360 invasive MRSA infections are diagnosed annually in the US, with 18,650 associated deaths. MRSA infections are typically classified as health care-associated or community-associated, with approximately 86% of all invasive MRSA infections health care-associated.6
Causes of MRSA
Ultimately MRSA is caused by bacterium strains that have acquired a resistance to particular antibiotics.
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. One study to determine the survival of resistant staph on common hospital surfaces looked at staph survival on five materials commonly found in hospital:8
100% smooth cotton (clothing)
100% cotton terry (towels and wash cloths)
60% cotton-40% polyester blend (scrub suits, lab coats and clothing)
100% polyester (privacy drapes, curtains and clothing)
100% polypropylene plastic (splash aprons).
Swatches of fabric were injected with 10,000 to 100,000 colony-forming units (CFU) of the microorganism and observed daily. Results showed 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 conclude the need for thorough contact control and meticulous disinfection procedures to limit spread of bacteria.
Health care-associated MRSA
MRSA frequently causes illness in people with a compromised immune system who interact with or reside in hospitals and health care facilities. This is referred to as health care-associated MRSA (or hospital-acquired MRSA) and often occurs for one of the following reasons:4
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.
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
The simple fact that hospitals and health care facilities are visited by large numbers of people, both patients and staff, providing an environment for bacteria to easily spread from person to person or person to object to person.
Those with a weakened immune system can include:
Patients in hospital for a long period of time
Patients on kidney dialysis (hemodialysis)
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.
Estimates suggest that 49-65% of health care-associated S. aureus infections are caused by methicillin-resistant strains.6
According to the Centers for Disease Control and Prevention (CDC) study, invasive health care-associated MRSA infections declined 54% between 2005 and 2011, with 30,800 fewer severe MRSA infections and 9,000 fewer deaths.9
A similar study conducted by the National Healthcare Safety Network (NHSN) found that rates of health care-associated MRSA bloodstream infections fell nearly 50% from 1997-2007.10
The average age of a person with health care-associated MRSA was 68.11
Who is at risk?
People most at risk of developing health care-associated MRSA in the hospital include those that have:
Weakened immune systems
A catheter or intravenous drip inserted
Burns or cuts to the skin surface
Severe skin conditions
Frequent antibiotics as part of their treatment.
Community-associated MRSA is contracted external to the hospital and is less widespread compared with health care-associated MRSA. Factors that cause increased risk of developing community-associated MRSA include:4
Regular skin-to-skin interaction for example in contact or collision sports such as rugby, ice hockey, soccer and basketball cause an increased risk of developing community-associated MRSA.
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
Unhygienic facilities or lack of personal hygiene
Previous antibiotics use.
The CDC reports that 14% of people with MRSA infections contracted them outside of the health care setting.
The average age of a person with community-associated MRSA was 23.11
The 5 Cs can be used to remember what factors make it easier for MRSA to be transmitted:4
Compromised skin (open wounds)
Contaminated (items and surfaces)
Cleanliness (lack of).
Recent developments on MRSA causes from MNT news
Gloves and gowns do not protect against MRSA or VRE, study shows
Researchers have found that wearing gloves and gowns in intensive care units does not reduce overall rates of acquiring MRSA or VRE, a study published online by JAMA has revealed.
MRSA traced back to cattle infections
A new study has suggested that a type of MRSA found in humans may have originated from cattle as far back as 40 years or more.
On the next page we take a close look at symptoms of MRSA, what antibiotic resistance means and the available tests and diagnosis options. On the final page we discuss treatment and prevention of MRSA.
Symptoms of MRSA
MRSA signs and symptoms depend on what area of the body is infected. Although many people carry MRSA bacteria in their mucosa (inside 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:12
Hot to the touch
Full of pus or other liquid
Accompanied by a fever.
Signs and symptoms of a serious MRSA infection in the blood or deep tissues include:
Fever of 100.4 degrees F or higher
Aches and pains of the muscles
Swelling and tenderness in the affected body part
Wounds that do not heal.
What is antibiotic resistance?7
Antibiotic resistance is a major issue driven by overuse of antibiotics and inappropriate prescribing practices. Consequences of antibiotic resistance and inappropriate use of antibiotics include:
Increased levels of disease and death
Increased duration patients have to stay in hospital
Increase in patients becoming colonized or infected with resistant bacteria
Difficulty in treating infection as resistance in bacteria grows.
Inappropriate use of antibiotics is thought to have initiated the development of resistance. Inappropriate use and prescribing includes:
Failing to complete a course of antibiotics as prescribed
Doses of antibiotics being skipped
Failure to take antibiotics at regular intervals
Saving antibiotics for a later date
Unnecessary prescription of antibiotics
Improper use of broad-spectrum antibiotics
Inappropriate selection and dose duration of antibiotics
Inappropriate use of antibiotics in animal agriculture.
In a vast population of bacteria, there may be some that are unaffected by the antibiotic, which survive and reproduce, producing more bacteria that are not affected by the antibiotic. The development of antibiotic resistance occurs in stages, including:
Changes or mutations occur in the genes of individual bacterial cells
Some mutations protect the bacterial cells from the effects of the antibiotic
Bacteria that do not have these protective mutations die and cannot reproduce as a result of antibiotic treatment
Bacteria with mutations (the resistant bacteria) enjoy increased opportunity for reproduction due to less competition from non-mutated bacterial strains eradicated by antibiotics.
MRSA Tests and diagnosis
When a staph infection is suspected, a physician or health care worker will take a “culture,” or sample of blood, urine, body fluid or a swab of a wound from a patient and send this to a laboratory for testing. If the test results are positive, additional tests can be completed to determine which antibiotic will kill the bacteria. MRSA strains are detected by analyzing which antibiotics are successful at eliminating the bacteria.
Bacteria under a microscope
MRSA strains are detected by analyzing which antibiotics are successful at eliminating the bacteria.
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%.
Recent developments on MRSA diagnosis from MNT news
Could genome sequencing of MRSA allow doctors to gauge strain severity?
By sequencing the genome of MRSA, scientists may be able to predict the severity of infection in an individual, according to a new study published in Genome Research.
MRSA infection rates decline from infection control certification
A new study, in the March issue of the American Journal of Infection Control, reveals that hospitals with a board certified director in infection prevention and control have substantially lower rates of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSI), compared with hospitals that are not led by a certified professional.
Treatment and prevention of MRSA
If MRSA is diagnosed, treatment will vary subject to the following factors:
Type of infection
Location of the infection
Severity of the symptoms
Antibiotics to which the specific strain of MRSA responds.
Management of MRSA skin and soft tissue infections may include:13
Pus drainage from lesion
Drained material sent for culture and susceptibility testing
Patients being provided with information on wound care and hygiene
Antimicrobial therapy (in cases of possible cellulitis without abscess).
Treatment options for MRSA skin and soft tissue infections may include:13
Treatment options for MRSA skin and soft tissue infections may include various types of antibiotics that the bacteria is not resistant to.
Tetracycline drugs – Doxycycline and Minocycline
Trimethoprim and Sulfamethoxazole
Research suggests that certain probiotic strains may help reduce susceptibility to active infection with MRSA. Reduced diversity and strength of the gut microflora leaves us vulnerable to opportunistic infections, while Lactobacillus species such as paracasei, and L. acidophilus, as well as Bifidobacteria animalis subsp lactis have been seen to offer a degree of protection against MRSA.
What are hospitals doing to prevent health care-associated MRSA infections?
Doctors, nurses and other health care providers have the following measures in place to prevent MRSA infections:14
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
Health care 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 cafeteria and stay in their room. The only exception to this rule is to visit other areas for treatment and tests
MRSA swabbing – to identify if some non-MRSA patients have MRSA on their skin.
What can be done to prevent community-associated MRSA?
The following actions can reduce risk of community-associated MRSA outside of hospitals:
Actions such as regular hand washing can reduce risk of community-associated MRSA outside of hospitals.
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.
Wounds infected with MRSA should be kept clean and covered with clean, dry bandages until healed to prevent the spread of infection to others.
Never attempt to drain the infection yourself – this could make the infection worse or spread to other people. If antibiotics are prescribed, make sure the full dosage is taken for the duration recommended by your doctor, even if the infection is getting better. Only stop taking medication if your doctor advises you to.
Recent developments on MRSA treatment from MNT news
A single shot of antibiotic ‘could be new MRSA treatment’
Researchers at Duke Medicine in Durham, NC, have found that a new single-dose antibiotic is as effective as the current standard treatment for methicillin-resistant Staphylococcus aureus, which involves a twice-daily infusion being given for up to 10 days.
Anthrax and MRSA antibiotic found in ocean
According to a paper published in Angewandte Chemie, his team recently unearthed a new chemical compound from the sea that may become an effective treatment against the potentially deadly bacteria anthrax and MRSA.
Could tapeworm drug be used to treat MRSA?
Researchers have discovered that a drug currently used to treat people with tapeworms may have the potential to be used to fight the notorious MRSA bacteria as well. The study, published in PLOS ONE, demonstrates that the drug niclosamide can suppress the growth of methicillin-resistant Staphylococcus aureus (MRSA) cultures in both laboratory dishes and infected nematode worms.
Common breast cancer drug could help tackle MRSA
Researchers have found that an existing drug used to treat breast cancer may be effective against one of the most common superbugs: MRSA.