Abstract:

Objective To determine the main epidemic isolate of methicillin-resistant Staphylococcus aureus（MRSA） in Hulunbuir,to study the correlation between gene types and resistance spectra,and to define the origin,transmission and epidemiological characteristics of MRSA. The results may help to find solutions to control MRSA infection and delay the emergence of vancomycin insensitive isolate. Methods Totally,55 non-duplicate MRSA isolates were collected from 5 hospitals from January 2012 to June 2017 in Hulunbuir. Vitek 2 Compact automatic identification system was used to identify the isolates and to perform antimicrobial susceptibility testing. Multilocus sequence typing（MLST） combined staphylococcal cassette chromosome mec（SCCmec） typing were used to determine the gene types of MRSA. Results A total of 6 types,including 2 un-typed isolates,were detected in the 55 MRSA isolates,and the predominant type was SCCmec type Ⅱ（58.18%）. Totally,10 types,including 2 new types,were identified in MLST,and the predominant type was ST59（50.91%）,followed by ST72（10.91%） and ST239（10.91%）. Combining SCCmec typing and MLST,the ST59-MRSA-SCCmecⅡ was the predominant type（38.18%）. The resistance rate of ST59 to ciprofloxacin and gentamicin was low（3.57%）,and no levofloxacin,moxifloxacin and rifampicin resistant isolates were determind;The resistance rates of ST239 to tetracycline,ciprofloxacin,levofloxacin,moxifloxacin,gentamicin and rifampicin were 83.33%. ST72 isolates were not resistant to other antibiotics except erythromycin and clindamycin. The resistance rate of erythromycin and clindamycin in ST239（66.67%） was lower than those in ST59（85.71%） and ST72（83.33%）. Conclusions The predominant type is ST59,followed by ST72 and ST239. Combining with SCCmec typing,the predominant isolate is ST59-MRSA-SCCmecⅡ in Hulunbuir. ST59 is sensitive to ciprofloxacin,gentamicin,levofloxacin,moxifloxacin and rifampin,while ST239 shows a different resistance spectrum and has a high drug resistance rate.

Key words: Methicillin-resistant Staphylococcus aureus, Genotyping, Drug resistance, Hulunbuir