Ann Lab Med.  2016 May;36(3):250-254. 10.3343/alm.2016.36.3.250.

Antimicrobial Resistance and Molecular Characteristics of Nasal Staphylococcus aureus Isolates From Newly Admitted Inpatients

  • 1Department of Laboratory Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China.
  • 2Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China.


Staphylococcus aureus, or methicillin-resistant S. aureus (MRSA), is a significant pathogen in both nosocomial and community infections. Community-associated MRSA (CA-MRSA) strains tend to be multi-drug resistant and to invade hospital settings. This study aimed to assess the antimicrobial resistance and molecular characteristicsof nasal S. aureus among newlyadmitted inpatients.In the present study, 66 S. aureus isolates, including 10 healthcare-associated MRSA (HA-MRSA), 8 CA-MRSA, and 48 methicillin-sensitive S. aureus (MSSA) strains, were found in the nasal cavities of 62 patients by screening 292 newlyadmitted patients. Antimicrobial resistance and molecular characteristics of these isolates, including spa-type, sequence type (ST) and SCCmec type, were investigated. All isolates were sensitive to linezolid, teicoplanin, and quinupristin/dalfopristin, but high levels of resistance to penicillin and erythromycin were detected. According to D-test and erm gene detection results, the cMLSB and iMLSB phenotypes were detected in 24 and 16 isolates, respectively. All 10 HA-MRSA strains displayed the cMLSB phenotypemediated by ermA or ermA/ermC, while the cMLSB CA-MRSA and MSSA strains carried the ermB gene. Molecular characterization revealedall 10 HA-MRSA strains were derived from the ST239-SCCmec III clone, and four out of eight CA-MRSA strains were t437-ST59-SCCmec V. The results suggest that patients play an indispensable role in transmitting epidemic CA-MRSA and HA-MRSA strains.


Staphylococcus aureus; CA-MRSA; Nasal carriage; Antimicrobial resistance; Molecular characteristics

MeSH Terms

Anti-Bacterial Agents/*pharmacology
Bacterial Proteins/genetics
Drug Resistance, Multiple, Bacterial/genetics
Methicillin-Resistant Staphylococcus aureus/*drug effects/genetics/isolation & purification
Microbial Sensitivity Tests
Nasal Cavity/*microbiology
Staphylococcal Infections/diagnosis/microbiology
Staphylococcus aureus/*drug effects/genetics/isolation & purification
Anti-Bacterial Agents
Bacterial Proteins
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