Molecular Epidemiological Investigation Of Methicillin-resistant Staphylococcus Aureus Isolates

Objective：1. To guide the prevention and infection control of MRSA,we investigatethe molecular epidemiology and antibiotic resistance of methicillin-resistantStaphylococcus aureus (MRSA) isolates in our hospital.2. To develop a rapid spa typing method for MRSA,we use HighResolution Melting (HRM) analysis on MRSA Protein A (spa) typing.Methods: In the study,120Staphylococcus isolates collected from The GeneralHospital Of Shenyang Military Region were subjected to antibiotic sensitivity test(agar dilution method),the antibiotics include oxacillin,clindamycin,ciprofloxacin,penicillin,erythromycin,gentamicin,rifampin,tetracycline,trimethoprim,sulfamethoxazole,levofloxacin,vancomycin.All MRSA isolates were typing by pulsed field gelelectrophoresis (PFGE),multilocus sequence typing (MLST),Staphyloccoccal cassettechromosome mec (SCCmec) typing and Staphyloccoccal protein A (spa) typing.Thespa typing was also used HRM analysis.Results:According to the results,the isolation rate of MRSA was65.14%in ourhospital.All the MRSA isolates were mainly distributed in ICU ward (26.8%),neurology ward (26.8%) and respiratory ward (16.9%).respiratory secretion(94.4%)was the major type of the sample. All MRSA isolates were sensitive to vancomycin,the antibiotic resistance rates of other antibiotics were as follows: oxacillin(100%)、clindamycin（100%）、ciprofloxacin（94.4%）、penicillin（100）、erythromycin（100%）、gentamicin（94.4%）、rifampin（19.7%）、tetracycline（100%）、 trimethoprimsulfamethoxazole（9.9%）、levofloxacin（94.4%）.According to the molecular typingresults,SCCmec Ⅱ was the most predominant type (63.4%),followed by SCCmec Ⅲ(31.0%).Four spa types were found in all MRSA isolates,and the most predominanttype was t570(74.65%),followed by t030(9.86%) and t002(9.86%). Three sequencetypes were detected in MLST typing, ST5(84.5%) and ST239(12.7%) were the major clones that were prevalent in our hospital. The results of spa typing by HRM analysiswere consistent with the results of spa typing by sequencing and PFGE typing.Conclusion：In summary,the type of ST5-SCCmecⅡ-t570was the major epidemicMRSA strain in our hospital.HRM analysis is an effective method for MRSA spatyping.