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Community-Associated MRSA
Approximately 25-30% of the population is colonized with Staphylococcus aureus. Typical sites are the anterior nares, axilla and/or groin areas. Introduction of penicillin and related antibiotics in the 1950s and 1960s was followed by rapid emergence of methicillin-resistant Staphylococcus aureus, or MRSA, in health care settings (healthcare-associated or HA-MRSA).
In the 1990s, new strains of MRSA emerged and began causing infections among people with no identifiable links to health care settings. Several deaths among children without the common risk factors for health care associated disease were reported and led to increased attention. These infections were designated Community-Associated or CA-MRSA. Additional attention resulted from outbreaks of CA-MRSA among sports teams, prisoners, children, American Indians and Alaska Natives, and among men who have sex with men. CA-MRSA most often causes skin and soft tissue infections (SSTIs), which are frequently misattributed to spider bites. Invasive infections can occur and can affect any organ system. The prevalence of CA-MRSA colonization in the general population is unknown. Colonization rates differ by region and by the specific population tested. A study of adults presenting to emergency departments nationwide in 2004 documented that MRSA was the leading identifiable cause of SSTIs, and that the majority were caused by so-called community-associated strains. Introduction of these strains into hospitals and other health care settings has now blurred earlier distinctions between HA- and CA-MRSA.
Individual MRSA infections are not reportable under N.C. law. Outbreaks, however, should be investigated by the local health director if they represent a significant threat to the public health (NCAC: 10A NCAC 41A .0103). Similarly, isolated cases that have potential to become a significant threat may require public health intervention. An outbreak is defined as 2 or more cases linked in time and place. Outbreak management will require local public health authorities to lead responses to raise awareness and implement prevention and control efforts.
Recognize outbreaks.
Do you have an outbreak or outbreak potential that represents a public health threat? Examples:
React to community concerns.
Evaluate community concerns by considering risk factors for transmission. The Five C's or conditions that facilitate transmission of MRSA are:
Respond with public health control measures:
Risk factor studies are sometimes warranted. Consider a study to identify risk factors when an outbreak occurs in a new setting, or results are likely to impact prevention or control measures.
Colonization surveys
Although often reported, colonization surveys are time and resource intensive and are not generally necessary to direct control or prevention efforts. Surveys should not take precedence over prevention and control efforts aimed at well-recognized and modifiable risk factors. If unusual epidemiologic features are recognized or suspected, these studies may be needed to identify risk factors for transmission or target control measures.
Decolonization
The term decolonization refers to an attempt to reduce or eradicate colonization with MRSA, usually by use of a combination of topical and/or systemic antimicrobials. Decolonization regimens are often prescribed by healthcare providers for patients with recurrent MRSA infections. However, decolonization is not routinely recommended as a measure to control outbreaks in the community.
In addition to specific settings previously described, outbreaks of community-associated MRSA (CA-MRSA) have also been investigated among the following groups:
Studies of MRSA outbreaks among these groups have not revealed previously unrecognized risk factors. General CA-MRSA prevention and control approaches should be adapted to each group as appropriate.
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