Molecular epidemiology of Staphylococcus aureus in households of children with community-associated S aureus skin and soft tissue infections.

Rodriguez M1, Hogan PG1, Burnham CA2, Fritz SA1.

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Abstract

OBJECTIVES:

Although colonization traditionally is considered a risk factor for Staphylococcus aureus infection, the relationship between contemporary S aureus colonization and infection is not well characterized. We aimed to relate the presence of colonizing and disease-causing strains of S aureus within individuals and households.

STUDY DESIGN:

In a prospective study of 163 pediatric outpatients (cases) with community-associated S aureus skin and soft tissue infections in St Louis, infection isolates were obtained from cases and colonization cultures were obtained from cases and their household contacts (n = 562). Molecular typing by repetitive sequence-based polymerase chain reaction was used to compare infecting and colonizing isolates within each case. The infecting strain from each case was compared with S aureus strains colonizing household contacts. The colonization status of cases was followed for 12 months.

RESULTS:

A total of 27 distinct strain types were identified among the 1299 S aureus isolates evaluated. Between 1 and 6 distinct strain types were detected per household. A total of 110 cases (67%) were colonized at 1 or more body sites with the infecting strain. Of the 53 cases with an infecting strain that did not match a colonizing strain, 15 (28%) had 1 or more household contacts with a colonizing strain that matched the infecting strain. Intrafamilial strain-relatedness was observed in 105 families (64%).

CONCLUSION:

One-third of cases were colonized with a different strain type than the strain causing the skin and soft tissue infection. Fewer than one-third of cases with discordant infecting and colonizing isolates could be linked to the strain from another household contact, suggesting acquisition from sources outside the household.

Published by Mosby, Inc.

KEYWORDS:

CA; Community-associated; MRSA; MSSA; Methicillin-resistant Staphylococcus aureus; Methicillin-susceptible Staphylococcus aureus; PFGE; Pulsed-field gel electrophoresis; Repetitive sequence-based polymerase chain reaction; SSTI; Skin and soft tissue infection; repPCR