Methicillin-Resistant Staphylococcus aureus (MRSA)

What Is MRSA?

Methicillin-resistant Staphylococcus aureus (MRSA) refers to strains of the bacterium Staphylococcus aureus (S. aureus), commonly referred to as staph, that are resistant to certain antibiotics (specifically, methicillin, a narrow-spectrum β-lactam antibiotic in the penicillin class, and other β-lactamase and penicillin antibiotics). Changes in the genetic makeup of S. aureus strains have given some bacteria the ability to become resistant to these antibiotics. S. aureus or staph is usually found in the nose and on the skin of about 30% of healthy individuals, while MRSA is found in only 2% of healthy individuals.¹ People who carry S. aureus or MRSA but do not have symptoms of an infection are considered to be colonized with the bacteria.

What Is a MRSA Infection?

People who have symptoms associated with MRSA or S. aureus colonizationare considered to have a MRSA or S. aureus infection. In the past, MRSA infections were typically confined to people who had been hospitalized; these infections are referred to as hospital-acquired MRSA (HA-MRSA) infections. However, MRSA infections can also be acquired by people who have not been hospitalized; these are known as community-acquired MRSA (CA-MRSA) infections.²

Signs and Symptoms of a MRSA Infection

Skin infections caused by CA-MRSA typically start as reddened and inflamed patches, pimples or bumps on the skin that may be painful, swollen or warm to the touch. If left untreated, these can develop into abscesses that drain pus and other fluids, or cellulitis (an infection of the tissues beneath the skin), or can cause fever. It’s not possible to determine whether you have a skin infection caused by MRSA just by looking at the infection, so you should see a doctor if you think you might have a MRSA infection, especially if the symptoms are accompanied by a fever.¹

In healthcare settings, MRSA is one of the leading causes of surgical site infections, bloodstream infections and pneumonia. These can occur in patients who have breaks in the skin that can allow the bacteria to enter the tissues or bloodstream, or in patients taking antibiotics, which can reduce the normal flora on the skin, giving MRSA an advantage.³ The symptoms of these infections are varied depending on the site of the infection but may include fever, chills, the draining of pus or other fluids, pain and swelling, a mucus-filled cough and stabbing pains in the chest. Life-threatening sepsis resulting from the body’s natural response to fighting infection may occur if left untreated.⁴

How Is MRSA Diagnosed?

MRSA infections are typically diagnosed if the organism can be successfully cultured (grown) from a sample taken from a wound or infected site. This typically takes about 48 hours. Newer diagnostic tests that identify DNA specific to MRSA are becoming available and can give a diagnosis in a matter of hours.⁵

Who Is at Risk?

Anyone is at risk of acquiring CA-MRSA. However, the CDC has identified five factors — the five Cs — that may make it easier for people in locations where these exist to acquire MRSA.⁶ These are  Crowding, frequent skin-to-skin  Contact,  Compromised skin (i.e., cuts or abrasions),  Contaminated items and surfaces, and lack of  Cleanliness. These factors are commonly found in schools, dormitories, military barracks, athletic gyms, households, correctional facilities, daycare centers, urban underserved communities, veterinary clinics and livestock settings.⁶ For example, athletes, especially those involved in sports with skin-to-skin contact such as wrestling, are particularly at risk, but there have been many reports of high-profile athletes contracting MRSA.⁷ Outbreaks have also occurred in the families of people who have had MRSA surgical site infections, and in people participating in group activities such as camping.² Because CA-MRSA usually manifests as a skin infection, people who are confined in close quarters such as detainees in jails or prisons, or who are in physical contact with each other such as athletes, are particularly at risk.

For HA-MRSA infections, because MRSA can enter any open wound or break in the skin (e.g., those resulting from IV catheter insertions), anyone who is hospitalized is at risk.⁸ Patients at higher risk include those who are already colonized with MRSA on admission to the hospital,⁹ those who have an IV line insertion or an invasive procedure such as a surgery, and long-term care facility residents.¹⁰

Based on 2005 CDC estimates for invasive MRSA infections and data on culture-confirmed CA-MRSA infections, it is likely that there are over 1.3 million MRSA infections in total, of which around 90% were CA-MRSA infections.² This 1.3 million figure includes MRSA infections of all types, the majority of which do not require hospitalization. Estimates of invasive MRSA infections date from 2011. That year, the CDC estimated there were a total of just over 80,000 invasive (life-threatening) MRSA infections. Of those 80,000 invasive infections, 60% were attributed to HA-MRSA and 18% were community-acquired infections that developed while the patient was in the hospital. The remaining 22% were attributed to MRSA infections that developed in the community.¹¹ The cost of treating a HA-MRSA infection has been estimated to be as high as $60,000 for a surgical site infection caused by MRSA.¹²

The Role of Direct Contact in the Spread of MRSA

MRSA is generally spread by direct skin-to-skin contact, or by contact with surfaces or shared items such as towels or bedding that have been contaminated through contact with an infected site of someone with a MRSA infection. The route of transmission helps to explain why the five Cs — crowding, contact, contamination, compromised skin and lack of cleanliness — are important contributors to the spread of MRSA.⁶ If you are colonized with MRSA and do not have an active infection, the risk of transmission is small. However, the transmission risk increases if you have an active infection such as a skin infection with pus or drainage. In these situations, good personal and environmental hygiene and covering open infections or sores can help prevent transmission.¹³

The Role of Surfaces in the Spread of MRSA

In the environment, S. aureus and MRSA can survive for between seven days and seven months on hard surfaces, with the length of survival dependent on conditions such as temperature and humidity.¹⁴ This means that in any setting — community or healthcare — there is a risk that surfaces that are not cleaned and disinfected regularly or correctly can harbor MRSA. Frequent touching of these surfaces can then transfer MRSA to hands, which can then contaminate other surfaces or transmit the pathogens to other people. This is a particular risk in healthcare settings where people are more likely to be susceptible to infection.

In 2011, the Infectious Disease Society of America (IDSA) issued comprehensive guidelines for the management of MRSA infections.¹⁵ Treatment very often requires the use of antibiotics, but there are only a few antibiotics to which MRSA is susceptible, including the broad-spectrum antibiotic vancomycin. Treatment regimens vary depending on the type of infection that CA-MRSA or HA-MRSA has caused.

In the case of CA-MRSA, abscesses resulting from skin and soft tissue infections (SSTIs) may require only incision and drainage, whereas more severe SSTIs may require the surgical removal of infected tissues and topical or intravenous administration of antibiotics. For many HA-MRSA infections such as bloodstream infections, pneumonia and surgical site infections, treatment with broad-spectrum antibiotics is usually required. There may also be special considerations for management of pediatric MRSA infections.¹⁵

Cleaning and Disinfection

Frequent cleaning and disinfection of potentially contaminated surfaces and equipment is an important step to take to prevent the transmission of MRSA, especially if someone in your household, facility or institution has a MRSA infection. According to guidance from the Centers for Disease Control and Prevention,¹⁶ it is important to select a disinfectant that has been approved by the Environmental Protection Agency (EPA) to kill S. aureus or MRSA (look for the list of microorganisms on the product label). Be sure to wear any protective equipment, such as gloves, that the label requires. If required by the directions for use, first clean off dirt and organic material; this will ensure that the disinfectant is effective. Also make sure the disinfectant stays wet on the surface for the contact time listed on the label. This is the time that the disinfectant must remain on a surface in order to be effective.¹⁶

Below are some Clorox Healthcare and CloroxPro disinfectant products that have EPA-approved claims to kill MRSA and S. aureus in the environment. Always follow the directions for use on the label when cleaning and disinfecting.

Hand Hygiene

Regular hand hygiene with soap and water or an alcohol-based hand sanitizer should be practiced by anyone who has a MRSA infection, those in close contact with them, and healthcare workers who are caring for patients with MRSA.

If You Have a MRSA Infection

The CDC also recommends a number of steps you can take to prevent the spread of MRSA and S. aureus in the community:⁶

• Cover wounds with clean, dry bandages, particularly if they are draining or have pus, which can contain MRSA and S. aureus. Discard used bandages or tape in the trash.
• Clean hands. Hand hygiene with soap and water or an alcohol-based hand sanitizer should be practiced by you, your family and others in close contact, especially after changing bandages or touching infected wounds.
• Do not share personal items such as uniforms, personal protective equipment, clothing, towels, washcloths or razors. Wash soiled clothing, sheets and towels, and dry them in a dryer on a hot setting, which will help to kill bacteria.
• Tell your doctor and any healthcare providers who treat you that you have or had a staph or MRSA skin infection.