Molecular characterization and antimicrobial resistance of nine strains of CA-MRSA isolated from clinical inpatients

Abstract

Objective: To investigate the molecular characterization and antimicrobial resistance of CA-MRSA(community-associated methicillin-resistant Staphylococcus aureus) strains isolated from clinical inpatientsto provide evidence for prevention and treatment of CA-MRSA infections. Methods: Isolates of S. aureus from hospitalized patients were collected within 24 h after admission from April 2014 to Dec. 2015, and mecA gene was detected to distinguish MRSA from MSSA (methicillin-sensitive Staphylococcus aureus). Genotypic CA-MRSA strains carrying SCC mec Ⅳ/Ⅴ were obtainedfor further analysis of molecular epidemiologic characters by spa-typing and MLST（multilocus -sequence typing）. Based on the CLSI (Clinical and Laboratory Standards Istitute) guidelines, disk diffusion method was used to test drug susceptibility of CA-MRSA strains. Moreover, the presence of pvl virulence gene was detected by PCR. Results: A total of 147 strains of S. aureus including 58 MRSA strains were collected from hospitalized patients. By SCCmec typing, 9 CA-MRSA strains (SCCmec Ⅳ 3; SCCmec Ⅴ 6) were detected. All CA-MRSA strains developed resistance against different non-β-lactams, among which 8 strains developed drug-resistanceagainst aminoglycosides (mainly kanamycin) and 8 strains developed drug-resistance against erythromycin and clindamycin mediated by erm(B) mainly. Molecular typing revealed that the main CA-MRSA clone was t437-ST59, and other clones were t034-ST804, t127-ST1, t008-ST8 and t437-ST338. In addition, 5 out of 9 CA-MRSA strains were pvl gene positive. Conclusions: More pathogenic CA-MRSA strains are invading healthcare-associated settings and developing more resistance against non-β-lactams, indicating that the CA-MRSA should be closely monitored in hospitals.

Keywords

• |community-associated methicillin resistant staphylococcus aureus|molecular characterization|antimicro-bial resistance