Analysis on inducible resistance of erythromycin and clindamycin in Staphylococcus aureus

Objective To investigate the resistance of Staphylococcus aureus isolates to erythromycin and clindamycin,and detect the frequency of inducible resistance of erythromycin to clindamycin.Methods According to the standards of Clinical and Laboratory Standards Institute(CLSI),disc diffusion method was used to test the methicillin-resistant Staphylococcus aureus(MRSA) and the resistance of Staphylococcus aureus to erythromycin and clindamycin.The inducible resistance phenotype of erythromycin to clindamycin was analyzed by double disc diffusion method(D test).Results The rate of MRSA in Staphylococcus aureus was 77.2%.The co-resistance strains to erythromycin and clindamycin in Staphylococcus aureus were 62.4%,and the erythromycin-resistant and clindamycin-susceptible strains were 21.5%.The positive rates of D test were 72.0% and 57.1% in erythromycin-resistant and clindamycin-susceptible MRSA and methicillin-sensitive Staphylococcus aureus(MSSA).D test positive strains accounted for 68.8% among erythromycin-resistant and clindamycin-susceptible strains.Conclusions The inducible resistance of erythromycin to clindamycin in Staphylococcus aureus should be detected by D test in clinical microbiology laboratory in order to guide physicians to select antimicrobial agents correctly such as macrolides and lincosamides.