MRSA fact sheet (PDF 216KB)
Public Health action
Public Health significance
MRSA may colonise or infect its host. MRSA is a cause of infection, including bacteraemia, wound infection, IV line sepsis, and pneumonia. There has been a significant increase in the number of MRSA notifications in Western Australia as a result of the increasing prevalence of local strains. Clusters of invasive infection with community MRSA are increasingly reported throughout Australia and internationally.
MRSA is resistant to treatment with all beta-lactam antibiotics (eg penicillins, cephalosporins), and invasive infection is associated with higher rates of treatment failure, morbidity and mortality compared with methicillin-sensitive Staphylococcus aureus.
Infectious agent
Methicillin resistant Staphylococcus aureus
Reservoir
Colonised patients with no apparent clinical infection are the major reservoir both in hospital and the community. A minority of total MRSA prevalence (approximately 15%) will be detected if microbiology cultures from sites of clinical infection alone are considered.
Mode of transmission
Direct contact. MRSA in either a healthcare or community setting can be transmitted to close contacts by both colonised and infected cases.
Incubation period
Variable and indefinite. Between 15% and 50% of newly colonised cases will develop invasive infection.
Communicability
Variable. Host factors (e.g. chronic skin lesions, URTIs), bacterial factors (e.g. specific strains), and environmental factors (eg hygiene, degree of close contact) affect transmissibility.
Susceptibility
Universal.
Methods of control
a. Preventive measures
Hand hygiene is the single most important measure to prevent transmission in a healthcare setting.
Standard and additional precautions should be used in healthcare facilities at all times (refer to OP 2039/06 Standard and additional infection control precautions).
Active surveillance programs (screening) are also of benefit in identifying colonised cases and contacts. This is particularly important in the situation of an outbreak or case-cluster of MRSA in either a healthcare setting or the community. The nose is the usual site of carriage, and active surveillance should be based on sampling of the anterior nares for appropriate microbiological testing.
b. Control of case
Decolonisation with topical and systemic agents is possible, although variably effective, and is likely to reduce the risk of invasive infection and transmission from a colonised individual.
Health Care Workers (HCWs) have been implicated in the acquisition and spread of MRSA in WA. Special consideration should be given to decolonise HCWs. GPs should liaise with HCW’s hospital infection control team for further guidance.
Treatment of an infected or colonised case depends on the clinical and epidemiological situation. In principle, if antibiotic treatment is required, the antibiotic susceptibility of an isolate should be assessed to guide therapy. Vancomycin is currently the treatment of choice for severe invasive MRSA infections. Further advice may be obtained from a consultant medical microbiologist or infectious diseases physician with appropriate expertise.
Note: For additional advice see the Operational Instructions OP 1922/05 Control of MRSA and Epidemic MRSA in hospitals and OP 1854/04 Guidelines for the management of MRSA in residential care facilities
c. Control of contacts
Patients who are MRSA contacts:
Refer to OP 2039/06.
Hospital Staff:
- All staff who have worked in a non-Western Australian hospital or health care facility in the previous 12 months must be screened and should be shown to be negative for MRSA before employment in a Western Australian hospital and before using hospital facilities (refer to OP 2039/06 Standard and additional infection control precautions)
d. Control of environment
See Operational Instructions listed below.
Epidemic strains of MRSA (EMRSA) are strains that have demonstrated the potential to cause outbreaks in health care facilities.
When an EMRSA strain is identified, the laboratory notifies the referring doctor. In a healthcare setting, hospital infection control staff are responsible for assessing the situation and implementing appropriate infection control measures. In a community setting, standard infection control precautions usually apply, with consideration as to whether there are close contacts of a case that could be at particular risk of developing invasive infection.
Additional sources of information
Exclusion
All staff who have worked in a non-Western Australian hospital or health care facility in the previous 12 months must be screened and should be shown to be negative for MRSA before employment in a Western Australian hospital and before using hospital facilities (refer to OP 2039/06 Standard and Additional Precautions).
Case definition
Laboratory criteria
Staphylococcus aureus which is:
- Resistant to methicillin (and all other B-lactam antibiotics)
All Western Australia laboratories should send all new methicillin-resistant Staphylococcus aureus isolates to the Gram Positive Bacteria Typing and Reference Unit at PathWest, together with the required information about the person from whom it was isolated.
