BACKGROUND: Community-associated methicillin-resistant Staphylococcus 
aureus-(CA-MRSA) strains have emerged in Argentina. We investigated the clinical 
and molecular evolution of community-onset MRSA infections (CO-MRSA) in children 
of Córdoba, Argentina, 2005-2008. Additionally, data from 2007 were compared 
with the epidemiology of these infections in other regions of the country.
METHODOLOGY/PRINCIPAL FINDINGS: Two datasets were used: i) lab-based prospective 
surveillance of CA-MRSA isolates from 3 Córdoba pediatric hospitals-(CBAH1-H3) 
in 2007-2008 (compared to previously published data of 2005) and ii) a sampling 
of CO-MRSA from a study involving both, healthcare-associated 
community-onset-(HACO) infections in children with risk-factors for 
healthcare-associated infections-(HRFs), and CA-MRSA infections in patients 
without HRFs detected in multiple centers of Argentina in 2007. Molecular typing 
was performed on the CA-MRSA-(n: 99) isolates from the CBAH1-H3-dataset and on 
the HACO-MRSA-(n: 51) and CA-MRSA-(n: 213) isolates from other regions. Between 
2005-2008, the annual proportion of CA-MRSA/CA-S. aureus in Córdoba hospitals 
increased from 25% to 49%, P<0.01. Total CA-MRSA infections increased 3.6 
fold-(5.1 to 18.6 cases/100,000 annual-visits, P<0.0001), associated with an 
important increase of invasive CA-MRSA infections-(8.5 fold). In all regions 
analyzed, a single genotype prevailed in both CA-MRSA (82%) and HACO-MRSA(57%), 
which showed pulsed-field-gel electrophoresis-(PFGE)-type-"I", 
sequence-type-5-(ST5), SCCmec-type-IVa, spa-t311, and was positive for PVL. The 
second clone, pulsotype-N/ST30/CC30/SCCmecIVc/t019/PVL(+), accounted for 11.5% 
of total CA-MRSA infections. Importantly, the first 4 isolates of Argentina 
belonging to South American-USA300 
clone-(USA300/ST8/CC8/SCCmecIVc/t008/PVL(+)/ACME(-)) were detected. We also 
demonstrated that a HA-MRSA clone-(pulsotype-C/ST100/CC5) caused 2% and 10% of 
CA-MRSA and HACO-MRSA infections respectively and was associated with a SCCmec 
type closely related to SCCmecIV(2B&5).
CONCLUSIONS/SIGNIFICANCE: The dissemination of epidemic MRSA clone, 
ST5-IV-PVL(+) was the main cause of increasing staphylococcal community-onset 
infections in Argentinean children (2003-2008), conversely to other countries. 
The predominance of this clone, which has capacity to express the h-VISA 
phenotype, in healthcare-associated community-onset cases suggests that it has 
infiltrated into hospital-settings.