BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause 
of both hospital and community infections globally. It's important to illuminate 
the differences between community-acquired MRSA (CA-MRSA) and hospital-acquired 
MRSA (HA-MRSA), but there have been confusions on the definition, especially for 
the MRSA isolates identified within 48 h of admission. This study aimed to 
determine the molecular characteristics and virulence genes profile of CA and 
HA-MRSA isolates identified less than 48 h after hospital admission in our 
region.
METHODS: A total 62 MRSA isolates identified within 48 h after admission and the 
clinical data were collected. Antimicrobial susceptibility test (AST) of 
collected isolates were performed according to the guidelines of Clinical and 
Laboratory Standards Institute (CLSI) 2015, and staphylococcal cassette 
chromosome mec (SCCmec) typing, multilocus sequence typing (MLST), pulsed-field 
gel electrophoresis (PFGE) and virulence gene profiling were performed to 
explore the molecular diversity.
RESULTS: SCCmec III and sequence type (ST) 239 were the most prevalent SCCmec 
type and ST in both CA and HA-MRSA groups. HA-MRSA group had higher prevalence 
of SCCmec III (87.2 %) and ST239 (79.5 %) compared with CA-MRSA (60.9 and 
43.4 %, both P < 0.001), while the frequency of SCCmec IV (26.0 %) and ST59 
(21.7 %) were higher in CA-MRSA than its counterpart (P < 0.001 and P = 0.003). 
MRSA-ST239-III was the predominant type in this study (61.3 %, 38/62), 
especially in HA-MRSA group (76.9 %, 30/39). However, CA-MRSA strains exhibited 
more diversity in genotypes in this study. Meanwhile, CA-MRSA tended to have 
lower resistant percentage to non-β-lactams antibiotics but more virulence genes 
carriage, especially the staphylococcal enterotoxins (SE) genes. Notably, seb 
gene was only detected in CA-MRSA isolates (52.2 %), likely a significant marker 
for CA-MRSA isolates. Panton-Valentine leukocidin gene (PVL) was highly detected 
in both groups, while appeared no significantly different between CA-MRSA 
(47.8 %) and HA-MRSA (43.6 %).
CONCLUSIONS: Our findings support a difference in the molecular epidemiology and 
virulence genes profile of CA-MRSA and HA-MRSA. Furthermore, this study 
indicates a possible transmission from HA-MRSA to CA-MRSA, which may cause the 
overlap of the definition.