Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Cystic Fibrosis Patients from Argentina

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) colonization in cystic fibrosis (CF) patients is an increasing problem in many countries. In our Respiratory Center at the Hospital de Nin˜os ‘‘Dr. Ricardo Gutie´rrez’’, Buenos Aires, Argentina, the prevalence has climbed from 23% in 1995 up to 32% in 2011. Our objective was to analyze the diversity of MRSA isolates recovered from respiratory samples of CF patients attending our center, characterizing their phenotypes and clonal distribution. Therefore, a prospective study was conducted on all CF patients attending the pediatric Respiratory Center between June 2012 and May 2013 to collect MRSA isolates. Antibiotic susceptibility testing, multilocus sequence typing, pulsed-field gel electrophoresis, spa typing, and agr genotyping were performed on collected isolates. The prevalence of MRSA during this period was 34.2%, and 71.9% of the patients were infected with isolates that carried SCCmec IV. High resistance rates were detected for gentamicin, erythromycin, clindamycin, ciprofloxacin, and rifampicin. Strains related to the communityassociated MRSA clones, ST5-IV and ST30-IV, were the most frequently recovered. Remarkably, even though most of the isolates were related to these clones, the rate of multi-resistance shown in CF patients was higher than that reported for the same lineages recovered from other infections in our country.