Study On The Detecting Methods And The Resistance Mechanism Of Methicillin-resistant Staphylococcus Aureus

Objective To evaluate the reliability and the clinical practicability of three methods for detecting meticillin-resistant staphylococcus aureus(MRSA) and offer a simple and convenient method in clinical Iab;To investigate the characteristics of resistance of clinical MRSA isolates in this locality and study the resistance mechanism of MRSA according to the result of SCCmec typing. Methods The sensitivities and specificities of cefoxitin disc diffusion method, oxacillin disc diffusion method and vitek instrumental method for detecting MRSA were compared according to the golden standards of mecA detecting; The antimicrobial sensitivity tests of staphylococcus aureus were tested by Vitek automatic microbial monitor GPS106;The characteristic genes of SCCmec typing were tested by PCR methods and the clinical islates of MRSA were typed by the results of characteristic genes. Results The sensitivities and specificities of oxacillin disc diffusion methods, cefoxitin disc diffusion method and Vitek instrumental method were 96.2%, 97.3%, 100%, 100% and 96.2%, 100% respectively according to the criteria of mecA gene detecting. The resistance rates to Ampicillin, Cefazolin, Chloramphenicol, Clindamicin, Erythromycin, Gentamicin, Rifampin, Tetracycline, Trimethoprim/sulfa and Levofloxacin of MRSA were higher than that of MSSA (P <0.05). MRSA were multi-resistant. The multi-resistant islates of MRSA were account for 94.1%, higher than that of MSSA(P <0.05). Among the 30 isolates of MRSA, 4(13.3%) isolates were belonged to SCCmec II genotype, 24 (80%) isolates were belonged to SCCmecIII genotype, 2(6.7%) isolates were belonged to SCCmecIV genotype and no isolates were belonged to SCCmec I genotype.