Analysis of Clindamycin-induced Resistance by Erythromycinamong 54 Staphylococcal Strains

Objective: To investigate the prevalence of inducible clindamycin resistance by erythromycin among Staphylococcus isolates and the effect of disk distance on test results. Methods: A total of 54 strains of Staphylococcus resistant to erythromycin and intermediate or susceptible to clindamycin were collected, including 20 strains of Staphylococcus aureus and 34 strains of Coagulase-negative Staphylococcus. The inducible clindamycin resistance by erythromycin (D Test) was tested by double disk diffusion method. Disk distance 15 mm and 26 mm were separately tested to examine the effect of disk distance on the results of D Test. Results: The prevalence of inducible clindamycin resistance was by erythromycin 51.90% in total, 70.00% in S.aureus and 41.20% in Coagulase-negative Staphylococcus, P 0.05. The further disk distance would affect the picking out rate of D Test. Conclusion: The detection of inducible clindamycin resistance by erythromycin in Staphylococcus isolates should be stressed in microbiology laboratory,for guidance of clinical treament of Staphylococcus infection.