Public health priority: not a notifiable disease. Public health units can assist with the control of outbreaks in the community.
Staphylococcus aureus (commonly known as golden staph) are bacteria commonly found on the skin and in the nose of people. Staph carriage is usually harmless but sometimes it can cause skin infections, abscesses, pneumonia, osteomyelitis and bacteraemia. Some strains of staph are resistant to the antibiotic methicillin and other antibiotics that were used in the past to treat infections. These are known as methicillin resistant Staphylococcus aureus (MRSA).
MRSA has previously been associated with health care facilities but it has recently been recognised that there are MRSA strains that can cause infections in otherwise healthy individuals. These strains are distinct from hospital strains and are referred to as community-acquired MRSA (CaMRSA).
The bacteria are easily shed from the skin and infected draining wounds. Purulent discharge contains high concentrations of the organism and is the most common source. Person-to-person transmission occurs through contact with a purulent wound through broken skin.
Because people can be colonised for months prior to infection, the incubation period is not well defined.
MRSA infections in the community usually manifest as skin infections such as pimples, boils, impetigo, furuncles, carbuncles, and abscesses. Septicaemia and pneumonia or osteomyelitis can also occur.
Infection with MRSA is confirmed:
MRSA is not a notifiable disease. Clinicians are encouraged to report to the public health unit if clusters of infection occur (i.e. two or more related cases). The response to a cluster should be carried out in collaboration with the cases' health carers. Treatment of individual cases is the responsibility of the doctor.
An investigation is required if ongoing transmission is occurring in a well-defined, closely-associated cohort (such as a household, classroom, childcare centre or sporting group). The response to an outbreak of skin and soft tissue infections due to MRSA will vary and may be influenced by the number of cases, the severity, the setting, and further public health risk. The following 10 steps provide a systematic approach to CaMRSA outbreak investigations.
A CaMRSA outbreak is defined two or more related cases of CaMRSA skin and soft tissue infections in a well defined, closely associated cohort. There are no data routinely collected on the incidence of skin and soft tissue infections (due to any cause).
It is important to make sure that the group of possible outbreak cases is actually experiencing the same illness. This is especially important for an outbreak defined by a symptom, such as skin infection, as there are many possible causes. To confirm CaMRSA infection, a wound swab should be taken for microscopy and culture. Alert the laboratory of the outbreak to guide testing procedures and to determine the estimated time frame for results.
Determining the strain involved in an outbreak, through molecular typing, can provide evidence of related cases and may provide insight to transmissibility and potential for environmental spread. Testing should be determined in consultation with microbiological experts and infectious diseases specialists where available.
A case definition should be developed specifying time, person and place. Identify the group of people who may have been exposed to CaMRSA. Cases should be interviewed about risk factors for illness including:
Describe the case data in terms of time, place and person and draw an epidemiological curve to display the number of cases by day of onset. Develop a line-listing of cases, including:
Consider the source of infection and the usual mode of transmission based on analysis of the data collected. Identify potential facilitators of ongoing infection and barriers to infection control.
Consider the source of the illness and the usual mode of transmission based on analysis of the data gathered on the place, time and personal characteristics of the cases, and exposure histories.
Consider whether an analytical study (usually a cohort or a case-control study to compare exposures, behaviours associated with CaMRSA transmission and hygiene practices) will provide useful additional information.
This may include an assessment of the environmental circumstances that could contribute to the outbreak (eg hand washing facilities and practices, towel sharing and washing) and further laboratory testing or screening of contacts.
The case or relevant care-giver should be informed about the nature of the infection, the mode of transmission and the importance of hand washing and good hygiene for preventing infection. In addition to providing general hygiene information, PHUs should assess the need for providing support and access to further prevention measures in schools, sporting groups, and other high risk groups including:
Current evidence does not support the routine use of agents to eliminate colonisation. However, it may be reasonable to try and eliminate staph carriage if:
Key points for a decolonisation procedure include:
Document findings to convey recommendations about the immediate control of CaMRSA outbreaks and to provide evidence for policies designed to prevent future outbreaks.
Communicate findings back to those affected by the outbreak and relevant health care providers.