Detection of mecA gene and drug-resistance analysis

Abstract

Objective To determine whether coagulase-negative non-epidermal staphylococcus is methicillin-resistant coagulase-negative staphylococcus by mecA gene test, when the minimal inhibitory concentration(MIC)of oxacillin is between 0.5-2.0 mg/L. Methods The mecA gene was detected and analyzed by the cefoxitin disk diffusion, E-test, VITEK-2 Compact and polymerase chain reaction(PCR)purification. Results A total of 300 strains of coagulase-negative staphylococci were screened from 4032 patients(7.4%), of which 45 strains of Staphylococcus saprophyticus and 80 strains of Staphylococcus hemolyticus were identified by Compact VITEK-2.There was a statistically significant difference in the positive rate of mecA gene detection between Staphylococcus saprophyticus and Staphylococcus hemolyticus(P<0.05). The results of detection of cefoxitin disk diffusion(inhibitory zone diameter ≥25 mm), E-test(MIC of oxacillin between 0.5-2.0 mg/L)and Compact VITEK-2(MIC of oxacillin between 0.5-2.0 mg/L)showed that there were 81 strains of coagulase-negative non-Staphylococci, of which 10 strains with positive mecA gene were confirmed by PCR. Conclusions When the minimal inhibitory concentration(MIC)of oxacillin against coagulase-negative non-Staphylococci stains is between 0.5-2.0 mg/L, the guidelines of the American clinical laboratory standardization institute(CLSI)should be strictly implemented in clinical microbiology laboratory and the mecA gene must be tested.Based on the wide dissemination of the mecA gene in Staphylococcus aureus population, if the mecA gene test is negative, it is reported as methicillin-susceptible coagulase-negative Staphylococcus(MSCNS), and the reverse result is reported as methicillin-resistant coagulase-negative staphylococcus(MRCNS). Key words: Coagulase; Methicillin resistant; Staphylococcus; mecA gene