MRSA: Methicillin-Resistant Staphylococcus aureus

What is Staphylococcus aureus?

• Staphylococcus aureus, often referred to simply as "staph," are bacteria commonly carried on the skin or in the nose of healthy people.  Approximately 25% to 30% of people in general are colonized (when bacteria are present, but not causing an infection) in the nose with staph bacteria. 

What is colonization?

• When a person carries the organism/bacteria but shows no clinical signs or symptoms of infection. For Staph aureus the most common body site colonized is the nose.

What is infection?

• When there are signs (such as fever, redness, swelling, discharge, heat at a location of an infection) or symptoms (feeling feverish, chills, pain, aches, weakness, malaise - not feeling well, nausea, vomiting) of infection in addition to laboratory evidence of infection, including a positive culture. 

What is MRSA (methicillin-resistant Staphylococcus aureus)?

• Some staph bacteria are resistant to antibiotics.  MRSA is a type of staph that is resistant to a class of antibiotics related to penicillin, which includes methicillin, oxacillin, penicillin and amoxicillin.  Approximately of 1% of people in general are colonized with MRSA, while people receiving certain types of healthcare, such as those receiving dialysis or living in nursing homes, are at increased risk of being colonized with MRSA. 

What is healthcare-associated MRSA (HAMRSA)?

• Staph infections, including MRSA, occur most frequently among persons in hospitals and healthcare facilities (such as nursing homes and dialysis centers) who have weakened immune systems. These healthcare-associated staph infections include surgical wound infections, urinary tract infections, bloodstream infections (including central-line associated bloodstream infections), and pneumonia. Click here for more information about HAMRSA: Who Is at Risk for Getting a MRSA Infection.aspx?

What is community-associated MRSA (CAMRSA)?

• Staph and MRSA can also cause illness in persons outside of hospitals and healthcare facilities. MRSA infections that are acquired by persons who have not been recently (within the past year) hospitalized or had a medical procedure (such as dialysis, surgery, catheters) are know as CA-MRSA infections. Staph or MRSA infections in the community are usually manifested as skin infections, such as pimples and boils, and occur in otherwise healthy people. Click here for more information about CAMRSA:  Who Is at Risk for Getting a MRSA Infection.aspx 

How do I know if I have MRSA?

• Your doctor may take a sample from your infected skin, nose, blood, urine or saliva and send it to the lab. This test sample is called a “culture”.  If the lab finds MRSA in the test sample, the test is positive; this means that you have MRSA in or on your body.  If you have a positive test but no signs or symptoms of an infection, you are probably colonized (carrying) MRSA but not infected. 

What is an MRSA bloodstream infection (BSI)?

• An MRSA BSI is when a patient has a positive test for MRSA in the blood along with evidence of an infection, such as a fever.  MRSA BSIs are often secondary infections; that is, the result of an MRSA infection in another place, such as the lungs (pneumonia) or a wound. 

What MRSA information is reported to the California Department of Public Health and where can I find that information?

• All California general acute care hospitals are required to report MRSA bloodstream infection (BSI) cases that occur following hospitalization so that CDPH can calculate the rates of MRSA BSI at each hospital and make that information available to the public (Health and Safety Code Section 1288.55).  The latest California hospitals MRSA BSI report is available at MRSA and VRE BSI Report Page . Comparison of the rates of MRSA BSI in different hospitals in this report should be avoided because differences may be due to variations in surveillance practices and/or laboratory testing methodology.