[Spread of genetically related methicillin-susceptible Staphylococcus aureus belonging to CC45, in healthy nasal carriers in Child Day Care Centers of Medellin, Colombia]

Introduction: Colonization plays a major role in the epidemiology and pathogenesis of Staphylococcus aureus infections. The child population is one of the most susceptible to colonization; however, community and children studies are limited in Colombia.

Objective: To assess the clonal relationship of S.aureus strains isolated from colonized children in eight day care centers (DCCs) from Medellin and to determine the presence of epidemiological characteristics in these populations.

Methods: An observational cross-sectional study was conducted on a sample of 200 children aged from 6 months to 5 years attending eight DCCs in Medellin, Colombia, during 2011. Nasal samples were collected from each nostril. The isolates species and methicillin resistance were molecularly confirmed using nuc and mec genes. Genotypic analysis included SCCmec typing, spa typing, PFGE and MLST. Epidemiological information was obtained from the parents and analyzed using the statistics program SPSS 21.0 RESULTS: The colonization frequency in DCCs ranged from 16.7% (n=3) to 53.6% (n=15). Genetically related isolates were identified inside four DCCs. Half (50%) of the isolates were grouped in 3 clusters, which belonged to the clonal complexes CC45, CC30, and CC121.

Conclusion: Molecular typing of isolates from colonized children and comparison among DCCs showed the spread of colonizing strains inside DCCs in Medellin; predominantly the CC45 clone, a successful child colonizer.