Methicillin-resistant Staphylococcus aureus (MRSA) burden is increasing 
worldwide in hospitals [healthcare-associated (HA)-MRSA] and in communities 
[community-associated (CA)-MRSA]. However, the impact of CA-MRSA within 
hospitals remains limited, particularly in Latin America. A countrywide 
representative survey of S. aureus infections was performed in Argentina by 
analyzing 591 clinical isolates from 66 hospitals in a prospective 
cross-sectional, multicenter study (Nov-2009). This work involved 
healthcare-onset infections-(HAHO, >48 hospitalization hours) and 
community-onset (CO) infections [including both, infections (HACO) in patients 
with healthcare-associated risk-factors (HRFs) and infections (CACO) in those 
without HRFs]. MRSA strains were genetically typed as CA-MRSA and HA-MRSA 
genotypes (CA-MRSAG and HA-MRSAG) by SCCmec- and spa-typing, PFGE, MLST and 
virulence genes profile by PCR. Considering all isolates, 63% were from 
CO-infections and 55% were MRSA [39% CA-MRSAG and 16% HA-MRSAG]. A significantly 
higher MRSA proportion among CO- than HAHO-S. aureus infections was detected 
(58% vs 49%); mainly in children (62% vs 43%). The CA-MRSAG/HA-MRSAG have 
accounted for 16%/33% of HAHO-, 39%/13% of HACO- and 60.5%/0% of 
CACO-infections. Regarding the epidemiological associations identified in 
multivariate models for patients with healthcare-onset CA-MRSAG infections, 
CA-MRSAG behave like HA-MRSAG within hospitals but children were the highest 
risk group for healthcare-onset CA-MRSAG infections. Most CA-MRSAG belonged to 
two major clones: PFGE-type N-ST30-SCCmecIVc-t019-PVL(+) and PFGE-type 
I-ST5-IV-SCCmecIVa-t311-PVL(+) (45% each). The ST5-IV-PVL(+)/ST30-IV-PVL(+) 
clones have caused 31%/33% of all infections, 20%/4% of HAHO-, 43%/23% of HACO- 
and 35%/60% of CACO- infections, with significant differences by age groups 
(children/adults) and geographical regions. Importantly, an isolate belonging to 
USA300-0114-(ST8-SCCmecIVa-spat008-PVL(+)-ACME(+)) was detected for the first 
time in Argentina. Most of HA-MRSAG (66%) were related to the Cordobes/Chilean 
clone-(PFGE-type A-ST5-SCCmecI-t149) causing 18% of all infections (47% of HAHO- 
and 13% of HACO-infections). Results strongly suggest that the CA-MRSA clone 
ST5-IV-PVL(+) has begun to spread within hospitals, replacing the traditional 
Cordobes/Chilean-HA-MRSA clone ST5-I-PVL(-), mainly in children. Importantly, a 
growing MRSA reservoir in the community was associated with spreading of two 
CA-MRSA clones: ST5-IV-PVL(+), mainly in children with HRFs, and ST30-IV-PVL(+) 
in adults without HRFs. This is the first nationwide study in Argentina 
providing information about the molecular and clinical epidemiology of CA-MRSA, 
particularly within hospitals, which is essential for designing effective 
control measures in this country and worldwide.