S. aureus ATCC 29213 (MSSA), Escherichia coli ATCC 35218 (for b-lactam ⁄ b-lactamase inhibitor combinations) and Pseudomonas aeruginosa ATCC 27853 (for Mueller–Hinton agar) were used for quality control of the susceptibility tests [13]. The inducible MLSB (iMLSB) phenotype was detected by the double erythromycin–clindamycin disk test