Methicillin-Resistant Staphylococcus aureus (MRSA)

1. Facts About 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

2. The Burden of MRSA Infections

Based on 2005 CDC estimates for 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. In 2011,  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

3. How Is MRSA Spread?

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.

4. MRSA Treatment

If MRSA is detected early, it can usually be treated effectively with antibiotics other than methicillin. It is important that individuals who think they might have a MRSA infection seek advice from a healthcare professional quickly so that the infection can be properly diagnosed and treated effectively. With skin infections caused by MRSA, antibiotics are rarely needed. Once the wound is open and drained of pus, it will normally heal on its own. Early diagnosis also ensures that appropriate measures can be taken to limit the spread of the infection.15

5. Preventing the Spread of MRSA

Cleaning and Disinfection

In order to prevent these infections, it is important to practise good hygiene. Keep your hands clean by washing thoroughly with soap and water or by using an alcohol-based hand sanitizer. Make sure that any cuts and scrapes are kept clean and covered until they have healed. It is also important to avoid unprotected contact with other people’s wounds or bandages. Finally, do not share personal items such as towels or razors.15 It is important to select a disinfectant that has been approved by Health Canada 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.

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

Product DIN no. Active ingredient Contact/Wet Time
(S. aureus
and MRSA)
Clorox Healthcare® Bleach Germicidal Wipes 02465671 Sodium hypochlorite 30 sec
Clorox Healthcare® Germicidal Disinfecting Cleaner 02469278 Sodium hypochlorite 1 min
Clorox Healthcare® Fuzion® Cleaner Disinfectant 02459744 Sodium hypochlorite 1 min
Clorox® Germicidal Bleach 02459108 Sodium hypochlorite 5 min
Clorox® Clean-Up® Disinfectant Cleaner with Bleach 02494019 Sodium hypochlorite 30 sec
Clorox Healthcare® Hydrogen Peroxide Cleaner Disinfectant Wipes 02406225 Hydrogen peroxide 1 min
Clorox Healthcare® Hydrogen Peroxide Cleaner Disinfectant 02403528 Hydrogen peroxide 30 sec
Clorox® Total 360® Cleaner Disinfectant 02460769 Quaternary ammonium chloride 2 min
Clorox® Disinfecting Wipes 02492636 Quaternary ammonium chloride 4 min

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

To prevent the spread of MRSA skin infections:15

  • Cover your wound. Any wounds that are draining or have pus must be kept covered with clean, dry bandages. Pus or other drainage from the wound can contain MRSA, so make sure that the bandages and tape are properly discarded. If you have questions about how to properly care for the wound, talk to your healthcare provider.
  • Wash your hands frequently. This is especially important after changing bandages or touching the infected area. By washing your hands you can stop the transmission of the bacteria.
  • Avoid sharing personal items. Bacteria can be transferred to another person through contact with items such as towels, razors or washcloths.
  • Make sure any soiled clothing is washed; water and regular laundry detergent is sufficient.
  • Talk to your doctor or healthcare provider. Tell them that you have, or have had a MRSA skin infection.


1. General information about MRSA in the community. Centers for Disease Control and Prevention website. Accessed December 27, 2017.
2. David MZ, Daum RS. Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic. Clin Micro Rev. 2010; 23(3):616–68.
3. Minnesota Department of Health. Causes and symptoms of HA-MRSA. Accessed January 8, 2018.
4. General information about MRSA in healthcare settings. Centers for Disease Control and Prevention website. Accessed January 8, 2018.
5. The Mayo Clinic. MRSA Infection. Diagnosis and Treatment. Accessed December 27, 2017.
6. CDC and the National Institute for Occupational Safety and Health (NIOSH). MRSA in the workplace. Centers for Disease Control and Prevention website. Accessed December 28, 2017.
7. National Geographic. Phenomena: A Science Salon. MRSA In Sports: Long Standing, Simple to Prevent, Still Happening. Posted October 10, 2015. Accessed December 28, 2017.
8. General information about MRSA in healthcare settings. Centers for Disease Control and Prevention website. Accessed December 27, 2017.
9. Datta R, Huang S. Risk of infection and death due to methicillin-resistant Staphylococcus aureus in long-term carriers. Clin Infect Dis. 2015;47(2):176-181.
10. The Mayo Clinic. MRSA infection. Accessed January 8, 2018.
11. Dantes R, Mu Y, Belflower R, et al. Emerging infections program–active bacterial core surveillance MRSA surveillance investigators. National burden of invasive methicillin-resistant Staphylococcus aureus infections, United States, 2011. JAMA Intern Med. 2013;173(21):1970-8. doi: 10.1001/jamainternmed.2013.10423.
12. Anderson DJ, Kaye KS, Chen LF, et al. Clinical and financial outcomes due to methicillin-resistant Staphylococcus aureus surgical site infection: a multi-center matched outcomes study. PLoS One. 2009;4(12):e8305.
13. Wisconsin Department of Health Services. MRSA methicillin-resistant Staphylococcus aureus – frequently asked questions. Accessed January 8, 2018.
14. Kramer A, Schwebke I, Kampf G. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infect Dis. 2006;6:130.
15. Public Health Agency of Canada, Fact Sheet – Community-Acquired Methicillin-Resistant Staphylococcus aureus (CA-MRSA) . Accessed August 24, 2020.