Healthcare Infection Prevention: CA-MRSA: Hospitals’ lessons may not apply
CA-MRSA: Hospitals’ lessons may not apply
We don’t . . . understand the method of spread’
Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is emerging in such a distinct epidemiological manner that the lessons gained from decades of dealing with MRSA in the hospital may not be particularly helpful in stemming an emerging public health problem, experts warn.
"I don’t think that the traditional MRSA models of hospital spread and all of the things we have learned about epidemiology necessarily apply to the community situation," said Robert Daum, MD, an epidemiologist at the University of Chicago Children’s Hospital. "There is a lot to learn here."
Distinct strains of CA-MRSA — with anti-biograms unlike their nosocomial cousins — are spreading among sports teams, within jails, and gradually becoming entrenched in communities. In one recent study, a surprising 8% to 20% of all MRSA collected as part of prospective population-based surveillance were not associated with traditional risk factors and were classified as community-associated.1
Speaking recently in Baltimore at the annual meeting of the Association for Professionals in Infection Control and Epidemiology (APIC), Daum said CA-MRSA is not like typical MRSA and can not necessarily be controlled using the same strategies.
"Many people are writing guidelines, but we don’t have the data to really understand the method of spread," he said.
"One good example of this is that Staph aureus has traditionally been a denizen of the nares. That’s where the organism lives when it asymtomatically colonizes us. But there have been repeated anecdotal lines of evidence and outbreak studies that have suggested that the noses of the people who are going to be infected [with CA-MRSA ] are clean," Daum pointed out.
"There is no Staph aureus colonization there. So one of the issues we have to try and understand is where is the organism living," he added.
As the situation worsens, there have been discussions about making CA-MRSA a reportable condition by state epidemiologists. However, the surveillance required is so labor-intensive that reportable CA-MRSA — if it is mandated at all — will likely be only for invasive infections.
"The information to distinguish community-associated [MRSA] and health care-associated involves both chart review and actually contacting the patients," said Rachel Gorwitz, MD, MPH, an epidemiologist in the division of health care quality promotion at the Centers for Disease Control and Prevention (CDC).
"It is very difficult. The overall burden of following both invasive and noninvasive was considered to be unsustainable by [surveillance sites that have tried it]. Health departments have to consider their available resources and the way they would be using the data. . . . We are not necessarily pushing for this to become reportable," she pointed out.
CA-MRSA may be something of a different animal, but Gorwitz pointed out some commonalties to APIC attendees that include the following risk factors for transmission:
- Crowding
- Frequent skin-to-skin contact
- Compromised skin
- Contaminated surfaces and shared items
- Lack of cleanliness
Summarizing meetings held between the CDC and a group of expert advisors on CA-MRSA, Gorwitz described some of the emerging strategies being discussed to meet the threat. "It’s important for providers to be aware that MRSA belongs in the differential diagnosis of [skin and soft tissue] infections compatible with staph. It also should be considered in the differential diagnosis of more severe disease."
Red flags raised during clinical evaluation include abscesses, pustular lesions, boils, suspected spider bites, and cellulitis. Such conditions may herald CA-MRSA, which also should be considered for more serious infections such as sepsis syndrome, osteomyelitis, necrotizing pneumonia, septic arthritis, and necrotizing fasciitis.
"It’s important to collect diagnostic specimens for culture, not only for clinical management of the individual patient, but [because] it contributes to our knowledge of the local prevalence, epidemiology, and susceptibility patterns," Gorwitz added.
In terms of patient management, incision and drainage often is required. "Incision and drainage should be routine," she said. "It’s considered the primary therapy for abscesses. It may be [the] sole therapy in some circumstances. It appears that many providers may no longer be as comfortable as they were with performing incision and drainage. So it may be important to provide provider education and refreshers."
In terms of antimicrobial selection, beta-lactams still are appropriate as first-line therapy for skin and soft tissue infections. Alternate agents to be considered include clindamycin, tetracyclines, rifampin (in combination with another agent), and linezolid. Agents such as macrolides and fluoroquinolones generally are not recommended for CA-MRSA because there is the potential for resistance to rapidly develop.
Adequate follow-up must be maintained for CA-MRSA patients because there is the possibility of progression to more severe infection.
Providers should develop a follow-up plan for all nonhospitalized patients. They should be instructed to return for care if they develop systemic symptoms, worsening local symptoms, or show no improvement after 48 to 72 hours.
Patient education critical
Critical components of case management include wound care, good hygiene, hand washing, and no sharing of potentially contaminated objects.
"Patient education is a critical component of case management," Gorwitz said. "Clinicians need to talk to their patients with skin infection about appropriate wound care and hygiene measures they can take at home to limit spread to their household members and other close contacts. A special circumstance that appears to happen not that infrequently is clusters of infections within a household where members appear to be ping-ponging infections back between each other, or [we see] individuals who have recurrent infections."
Instruct patients and household members to seek care early so prompt appropriate treatment of new infections can be provided.
"An additional strategy that could potentially be considered is decolonization, which as you know can consist of nasal decolonization with agents such as mupirocin, use of antiseptic body washes such as chlorhexidine, or in the case of individuals who also have active infections, oral antimicrobials that achieve high concentrations such as rifampin in combination with other agents," she said.
Data from health care settings (pre-op, dialysis, long-term care) demonstrate that these regimens can be effective in eliminating colonization, at least in the short term. "However, their effectiveness in preventing disease is less clear," she said. "There are almost no data on their effectiveness in the community setting."
Indeed, as Daum noted previously, nasal carriage is not necessarily a foregone conclusion with CA-MRSA. In addition, drug resistance can emerge during decolonization efforts, so the CDC currently recommends that the basic control strategies should be exhausted before decolonization is attempted.
Public health interventions for CA-MRSA outbreaks in the community should include enhanced surveillance, empiric therapy targeted to the pattern of the outbreak strain, and education on wound care and wound containment.
"In some circumstances, such as day care or sports team participation, it may be necessary to exclude patients if they are unable to keep their wounds covered or unable to maintain appropriate hygiene," Gorwitz said.
"Although the role of the environment in transmission isn’t clear, there have been certain investigations where an environmental source has been implicated so it makes sense to achieve and maintain a clean environment," she adds.
A CDC priority for CA-MRSA research is risk factors for transmission, including the sites and implications of colonization, the role of the environment, and transmission from companion animals. Research on management strategies includes decolonization and educational approaches. Laboratory work is being done to improve surveillance, and vaccine development eventually may provide a long-term solution.
"Various studies are under way, and more are needed to determine best methods for control and prevention of MRSA in the community," she explained. "However, strategies focusing on increased awareness, early detection, and appropriate management, enhanced hygiene and maintenance of a clean environment, appear to have been successful."
Reference
- Fridkin SK, Hageman JC, Morrison M, et al. Methicillin-resistant Staphylococcus aureus disease in three communities. N Engl J Med 2005; 352:1,436-1,444.