Molecular typing and antibiotic resistance of methicillin-resistant Staphylococcus aureus isolated from nasal swabs among patients with type 2 diabetes in community

Abstract

Objective To determine the molecular characteristics and antibiotic susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) isolated from nasal swabs among patients with type 2 diabetes in community. Methods Nasal swabs were collected from 417 patients with type 2 diabetes in 11 communities of Lishui Town, Foshan City, from April 2014 to June 2014. Staphylococcus aureus was determined after bacteria isolation and identification. Cefoxitin disk diffusion test and mecA gene polymerase chain reaction (PCR) assay were applied to detect MRSA. The staphylococcal cassette chromosome mec (SCCmec) typing of MRSA was conducted by multiplex PCR assay and the sequence type (ST) typing of MRSA was determined by multilocus sequence typing (MLST) based on the sequence of 7 housekeeping genes of MRSA. The antibiotic susceptibility of MRSA was tested by K-B disk diffusion. Results A total of 22 MRSA strains were isolated from the nasal swabs of 417 patients, including 1 strain of SCCmecⅠ (4.5%), 3 strains of SCCmecⅡ (13.6%), 3 strains of SCCmecⅢ (13.6%), 6 strains of SCCmec Ⅳ (27.3%), 4 strains of SCCmecV (18.2%) and 5 strains non-typeable (22.8%). Sixteen STs were found with MLST, of which 70% were ancestral ST for each clonal complex. MRSA isolates had high resistance rates to erythromycin, teicoplanin, clindamycin, moxifloxacin, tobramycin (81.8%, 59.1%, 59.1%, 36.4% and 31.8%, respectively), and all of MRSA isolates but 1 strain of SCCmec Ⅳ were sensitive to linezolid. And 68.2% of MRSA isolates were multi-drug resistant bacteria. Conclusions MRSA colonization is found in noses of patients with type 2 diabetes in community. The gene variation of MRSA isolates is low and its evolution is stable. Linezolid should be the prior choice for community infection of MRSA. Key words: Diabetes mellitus, type 2; Methicillin-resistant Staphylococcus aureus; Nose; Drug resistance; Molecular typing