Research of Mutations of Genes mecR1 and mecI in Clinical Staphylococci Isolates / 医学研究杂志

ABSTRACT

Objective To investigate mutation and deletion of genes mecR1 and mecI in clinical methicillin-resistant staphylococci isolates and study the mutation and deletion have effect on gene mecA expression and drug resistance phenotype.Metheods PCR was used to detecte gene mecA and the regulatory genes mecR1 and mecI in staphylococci which were separated from clinical specimen in 2006,then the sequence of gene mecI was determined and compared with the sequence obtains from pre-MRSA strain N315(GIBA000018).Results Gene mecA was detected in 60 strains of Staphylococcus aureus,58 strains of Staphylococcus epidermidis and 37 strains of Staphylococcus heamolyticus,but gene mecA in 6 strains of Staphylococcus epidermidis and 4 strains of Staphylococcus heamolyticus were only amplified by primer mecA2-F/R and not by primer mecA1-F/R.The percentage of gene mecR1 exist in Staphylococcus aureus was higher than Staphylococcus epidermidis and Staphylococcus heamolyticus,but the percentage of gene mecR1 exist in Staphylococcus epidermidis was not higher than Staphylococcus heamolyticus.The mutation and deletion of gene mecI were often seen,the wild type mecI was only detected in 14 strains,the point mutation of nucleotice 202 was detected in 36 strains.Conclusions Gene mecA expression in Staphylococcus aureus could be chiefly induced by mecR1,but which in coagulase-ngeative staphylococci could be other factors.The mutation and deletion of mecI were universal phenomenon in clinical strains,there could be a mechanism for overcoming the repressing of resistance caused by mecI in staphylococci.