1. Streptococci Vs Ery 5/Da 2 Multiple mechanisms of resistance Macrolides (eryth., clarith., roxith.) Lincosamides (clindamycin, lincomycin) 1.Ribosomal modification (erm gene) conferring resistance to all macrolides and lincosamides constitutive (R/Ery,Da) or inducible (R/Ery, S/Da, ICR+ ) 2.An efflux pump (mef gene, R/Ery, S/Da, ICR-) 3.Unknown mechanism (S/Ery, R/Da)

2. Streptococci Vs Ery 5/Da 2 Phenotypes 1.S/Ery, S/Da 2.R/Ery, R/Da (constitutive) 3.R/Ery, S/Da, ICR+ (report as R/Da) 4.R/Ery, S/Da, ICR- (efflux, report as S/Da) 5.S/Ery, R/Da (unknown mechanism, report S/Ery, R/Da ) Ery 5 and Da 2 in adjacent positions (13 mm) Note: Corynebacterium sp. isolates are tested the same way - Ery 5 and Da 2 (13mm)

3. Staphylococci Vs Ery 5/Da 2 Multiples mechanism of resistance Macrolides (eryth., clarith., roxith.) Lincosamides (clindamycin, lincomycin) 1.Ribosomal modification (erm gene) conferring resistance to all macrolides and lincosamides constitutive or inducible (R/Ery, S/Da, ICR+ ) 2.An efflux pump (mef gene, R/Ery, S/Da, ICR-)

4. Staphylococci Vs Ery 5/Da 2 Phenotypes 1.S/Ery, S/Da 2.R/Ery, R/Da (constitutive) 3.R/Ery, S/Da, ICR+ (report as R/Da) 4.R/Ery, S/Da, ICR- (efflux, report as S/Da) Ery 5 and Da 2 in adjacent positions (15 mm)

5. An MRSA isolate resistant to erythromycin with a large flattened clindamycin zone (R/Ery, S/Da, ICR+) Report: R/DaDa 2/Ery5: 15 cm edge to edge

6. The same MRSA isolate (R/Ery, S/Da, ICR+) Da 2/Ery5: 18 cm edge to edge

7. An MRSA isolate resistant to erythromycin with a large flattened clindamycin zone (R/Ery, S/Da, ICR+) Report: R/DaDa 2/Ery5: 15 cm edge to edge

8. An MRSA isolate resistant to erythromycin and susceptible to clindamycin (R/Ery, S/Da, ICR-) Report: S/Da