CONICET | Buscador de Institutos y Recursos Humanos

Background: Despite the widespread emergence of CA-MRSA causing infections in our country, no studies of S. aureus carriage have been performed in Argentina. Our goal was to determine carriage rates of S. aureus and MRSA in a small city of Buenos Aires Province, using as the study the whole population of healthy children (and their contacts) who were attending to the last year of kindergarten, and characterizing molecular characterization of the recovered isolates. Methods: Nasal, inguinal, axillary and pharyngeal swabs were taken from a total of 316 healthy kids. Samples were inoculated directly onto mannitol-salt agar and Chromagar MRSA plates. Antimicrobial Susceptibility was performed by disk diffusion tests. Detection of mecA, Panton-Valentine gene and SCCmec typing were done by PCR. MRSA isolates were genotyped by spa typing and PFGE. Results: Of 316 children evaluated, 84 carried MSSA and 14 MRSA. Contacts of this group were screened and MRSA was detected in 5/14 families. Only 2 of 14 MRSA isolates were resistant to erythromycin. All of these isolates harbored SCCmec IV and 4 carried PVL gene. By contrast, not a single contact from a control population of 25 MSSA positive children carried a CA-MRSA. 8/14 CA-MRSA could be grouped into one major clonal type as detected by PFGE, which could be divided in two subtypes. One of them, including the 4 PVL positive isolates, was recovered from children attending the same institution. During the follow up, not a single case of infection caused by MRSA was registered among the studied population. Conclusions: Carriage rate was 4.5% among healthy children, and it was not always present among members of their family. The PVL positive subtype is closely related to the prevalent CA-MRSA clone, (SCCmec IV, spa 311, ST 5) causing severe CA-MRSA infections in our country.

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