Agreement between Azithromycin and Erythromycin to Determine Inducible Clindamycin-Resistant Phenotypes in Staphylococcus aureus Isolates

Objectives To evaluate agreement in the detection of inducible clindamycin resistance by test method using azithromycin disk with reference method using erythromycin disk and to determine prevalence of inducible clindamycin-resistant phenotypes among Staphylococcus aureus isolates. Materials and Methods A total of 133 nonduplicate isolates of S. aureus from clinical samples were included in this prospective study. Agreement between erythromycin (reference method) and azithromycin (test method) disks for detection of inducible clindamycin resistance in S. aureus isolates was assessed. Statistical Analysis Chi-square test was used for analyzing categorical variables ( p < 0.05 was considered significant). Results The prevalence of inducible clindamycin resistance (iMLSB) was 15.8%. A 100% agreement was recorded between reference and test methods for detecting inducible clindamycin-resistant phenotypes. For the determination of constitutive-resistant phenotypes (cMLSB) among S. aureus isolates, the test method demonstrated an agreement of 94.1%. Conclusion The present study demonstrated an agreement in the identification of inducible clindamycin-resistant phenotypes among S. aureus isolates by both erythromycin and azithromycin disks.