IDSA releases first MRSA treatment guidelines

Staphylococcus aureus bacteria
Staphylococcus aureus bacteria

Authoritative practice guidelines for treating methicillin-resistant Staphylococcus aureus (MRSA) infections are now available from the Infectious Disease Society of America.

A 13-person expert panel addressed 11 different areas of treatment in the recommendations, which were published online in Clinical Infectious Diseases.  Although MRSA has been around for a long time, the increasing prevalence of community-acquired strains during the last decade has complicated treatment, the researchers noted.

After analyzing hundreds of MRSA case reports and clinical studies the panel created standardized guidelines for the following topics:

Managing initial and recurrent skin and soft tissue infections (SSTIs), bacteremia and endocarditis, pneumonia, bone and joint infections and central nervous system infections.

  • Treating neonatal MRSA infections.
  • Optimal vancomycin dosing and monitoring policies.
  • Using vancomycin susceptibility test results.
  • Managing vancomycin treatment failure and persistent bacteremia.
  • Using adjunctive therapies.

The recommendations emphasized using incision and drainage whenever possible and noted that this treatment likely sufficient for minor MRSA SSTIs, such as superficial abscesses and boils.

Treatment with clindamycin, trimethoprim-plus-sulfamethoxazole, a tetracycline or linezolid is recommended for outpatient empirical treatment of more serious SSTIs.

IV antibiotics, including vancomycin, daptomycin, telavancin or beta-lactams, should be considered for hospitalized patients with complicated SSTI, with the clinician's choice depending on the patient's clinical presentation.

Despite acknowledging poor quality of evidence for nasal and topical decolonization practices, the guidelines suggest that these options are appropriate for patients with persistent and recurrent infections.

In addition, the committee identified the following areas for further study: determining optimal antibiotic dosing for pediatric populations; the exact benefit of antibiotics for patients with simple skin abscesses; optimal therapy for osteomyelitis; the proper interval for switching antibiotics after bacteremia has resolved; and safety and effectiveness of echocardiography for patients with MRSA endocarditis.

Despite acknowledging poor quality of evidence for nasal and topical decolonization practices, the guidelines suggest that these options are appropriate for patients with persistent and recurrent infections.

MRSA colonization

Although the IDSA recommendations did not address routine infection control or surveillance, research from a separate study published in the Journal of Clinical Microbiology sheds new light on MRSA colonization – an important factor in disease transmission.

Leonard Mermel, DO, medical director in the department of epidemiology and infection control at Rhode Island Hospital in Providence and colleagues, analyzed the quantity of MRSA at different body sites among 60 inpatients.

They found that nasal cultures were more sensitive than those taken from the axilla (P<.001), groin (P=0.003) or perineum (P<.001), and that patients who were colonized in the nares were also more likely to be colonized at other body sites.

Combined, the nares and groin had a sensitivity of 98% and a negative predictive value of 88%, the researcher determined.

“This study shows us that the quantities of MRSA at different body sites are highly correlated. Also, if screening cultures are to be done for MRSA, it is best to screen the nose and groin to get the highest yield,” Mermel said in a press release.

There was no correlation between the number of body sites colonized with MRSA and patients' likelihood of having an active infection at the time of culture or during the year prior. Surprisingly, the researchers found lower quantities of MRSA among patients with active MRSA infection.

“We hope that future studies will assess whether or not a greater number of body sites colonized with MRSA or a greater quantity of MRSA at those body sites impacts the likelihood of future MRSA infection,” Mermel said.

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