Research Activities, January 2014
Despite use of topical antimicrobial therapies for MRSA decolonization, resistance remains low
Patient Safety and Quality of Care
A current epidemic of skin abscesses associated with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains has led physicians to consider two topical antimicrobial agents (mupirocin and chlorhexidine) to prevent recurrent skin infections in the outpatient setting. However, a new study found that although mupirocin resistance in S. aureus was infrequent in the patients studied, when present, it resulted in less successful eradication efforts in those patients. Mupirocin and chlorhexidine have been widely used to prevent healthcare-associated MRSA infections in patients in intensive care, or who are undergoing surgery or dialysis.
The researchers studied outcomes of patients with CA-MRSA skin and soft tissue infections, who were treated with a 5-day regimen of mupirocin and/or chlorhexidine. They recruited patients at least 6 months old who had community-onset skin and soft tissue infections from the emergency departments of pediatric and adult tertiary hospitals and 9 pediatric practices associated with a practice-based research network in St. Louis, MO.
The overall prevalence of resistant strains was low—2.1 percent for mupirocin (23/1,089 patients) and 0.9 percent for chlorhexidine (10/1,089 patients). However, patients with a mupirocin-resistant strain were significantly more likely to remain colonized with the bacteria after using the mupirocin for the 5-day regimen. Four patients found to carry mupirocin-resistant strains of S. aureus at baseline (that is, before decolonizing treatment with the drug) remained colonized with S. aureus after 1 month, in contrast to successful decolonization in 66 percent of 324 patients carrying mupirocin-sensitive strains at baseline. The percentages of patients with baseline chlorhexidine-resistant and baseline chlorhexidine-susceptible S. aureus colonized after 1 month were equivalent (50 percent and 48 percent, respectively).
Finally, the researchers noted that the mupirocin- and chlorhexidine-resistant strains of S. aureus were not derived from a single clonal type. Rather, 16 different strain types were detected among 113 CA-MRSA isolates resistant to mupirocin and/or chlorhexidine. The study was funded in part by AHRQ (HS21736).
More details are in "Mupirocin and chlorhexidine resistance in Staphylococcus aureus in patients with community-onset skin and soft tissue infections," by Stephanie A. Fritz, M.D., M.S.C.I., Patrick G. Hogan, M.P.H., Bernard C. Camins, M.D., M.Sc., and others in Antimicrobial Agents and Chemotherapy 57(1), pp. 559-568, 2013.