Detection of erythromycin-induced resistance to clindamycin among 216 strains of staphylococcus aureus

Objective To investigate the resistance of staphylococcus aureus(SA) to erythromycin and clindamycin, and detect the incidence of erythromycin-induced resistance to clindamycin.Methods Disk diffusion susceptibility method was performed for erythromycin and clindamycin according to the Clinical and Laboratory Standards Institute(CLSI). The inducible resistance phenotype was analyzed by clindamycin and erythyomycin double-disk diffusion method(D test) and VITEK 2 Compact AES.Results Analyzing the susceptibility of 216 SA strains, 76 strains(22 strains of MSSA, 54 strains of MRSA) were resistant to erythromycin but sensitive to clindamycin. 29 of the 76 strains were positive in D- test(8 strains of MSSA, 21 strains of MRSA); the positive rates were 36.4% and 38.9% respectively.Conclusion The occurrence of induced resistance to clindamycin is considerably high. It suggested that D-test should be routinely performed in erythromycin-resistant but clindamycin-sensitive staphylococcus in microbiological laboratories. The report of inducible clindamycin resistance is significant evidence to guide clinical physicians to use antibiotic correctly.