Source: Rodriguez M, Hogan GH, Burnham CA, et al. Molecular epidemiology of Staphylococcus aureus in households of children with community-associated S aureus skin and soft tissue infections. J Pediatrics. 2014; 164(1): 105– 111; doi: 10.1016/j.jpeds.2013.08.072Investigators from Washington University, St Louis, sought to determine if staphylococcal skin and soft tissue infections (SSTI) in children were acquired endogenously or from household members. Eligible patients (cases) were between 6 months and 20 years of age with a culture-confirmed methicillin-resistant Staphylococcus aureus (MRSA) or methicillin-susceptible S aureus (MSSA) SSTI and were also colonized with S aureus in the anterior nares, axillae, or inguinal folds. Molecular typing was done to compare colonizing and infecting isolates in children with S aureus SSTI and their household contacts.Baseline colonization status was assessed for household contacts and index cases. Only the index cases were assessed for colonization status at 1-, 3-, 6-, and 12-month follow-up visits. PCR testing was performed on isolates from household contacts and on infecting and colonizing isolates of the index case at baseline and on any colonizing isolates at the 4 follow-up visits.In all, 163 cases and 562 household contacts were studied. At baseline, 64% of cases were colonized with MRSA, 28% with MSSA, and 9% with both; 68% were colonized at a body site proximal to the infection site. MRSA was cultured from the SSTI in 81% and MSSA in 19% of the index cases. Of the 562 household contacts, 55% were colonized with S aureus: MRSA in 20%, MSSA in 33%, both in 2%. Contacts colonized with MRSA were significantly more likely to have had a SSTI in the past year compared to those not colonized with MRSA (36% vs 17%).There were 27 distinct strains of S aureus identified from all of the 1,299 S aureus isolates. At baseline, 67% of the infected children had at least 1 colonizing strain that matched the strain cultured from their infected site and in 46% there was concordance with a household contact. Of those index cases whose infecting strain did not match the colonizing strain (32%), 28% had at least 1 household contact with a colonizing strain that matched the infecting strain. Over the 12 months of study, index cases carried up to 6 distinct strain types and during this time, 72% were colonized with at least 1 strain that matched the baseline infecting strains.The authors conclude that one third of the children with SSTI were not colonized with the infecting strain, and among these children only about one quarter had a concordant strain in a household contact. This suggests that S aureus infections are acquired from both within and outside the household.Dr Crandall has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.S aureus infections cause a broad range of clinical manifestations including SSTIs, bacteremia, and bone and joint infections. Historically MRSA was associated with hospital acquisition; however, community-associated MRSA (CA-MRSA) has emerged as a prevalent pathogen.1,2The epidemiology of SSTIs in the pediatric population is not completely understood but colonization with CA-MRSA is an established risk factor for acute infections.3 Strategies to prevent SSTI in children have focused on decolonizing the affected person and/or household with a regimen of intranasal antibiotic therapy in conjunction with antiseptic body washes. Although prophylactic decolonization is effective at decreasing S aureus carriage, it does not reduce the incidence of first-time SSTIs.4 Targeted decolonization of individuals with recurrent SSTIs and/or their household contacts, on the other hand, results in a modest reduction in recurrent SSTIs.5 However, it is unclear if removal of colonizing S aureus strains increases risk for acquisition of more virulent strains. Decolonization is currently only recommended in individuals and households with recurrent SSTI.6Overall, the results of this study indicate that a substantial number of SSTIs in children are caused by a strain of S aureus acquired outside the household. These results highlight the need for further investigation into the transmission of CA-MRSA in order to develop more effective strategies for disease prevention.While we await the unraveling of the mysteries of the ecology of MRSA, consider these measures which may decrease the household transmission: cessation of sharing personal items such as towels and washcloths, lotions, and bar soap, as well as the institution of dilute bleach baths (see AAP Grand Rounds, February 2012;27[2]:197).
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