Molecular epidemiology, antimicrobial susceptibilities and resistance mechanisms of Streptococcus pyogenes isolates resistant to erythromycin and tetracycline in Spain (1994–2006)

Table 1 Distribution of phenotypes and genotypes among macrolide-resistant S. pyogenes isolates

Phenotype	No. isolates (%) Invasive/non-invasive	Antimicrobial agent(mg/L)				Macrolide resistance genotype
			Range	MIC50	MIC90	*erm (B)*	*erm (A)*	*mef (A)*	*msr (D)*	None gene
M	227 (76.9)	Erythromycin	1- ≥ 256	32	128	50	87	224	221	1
M	38 / 189	Clindamycin	0.06-0.5	0.25	0.5	50	87	224	221	1
cMLS_B	60 (20.3)	Erythromycin	8- ≥ 256	≥256	≥256	57	11	36	17	2
cMLS_B	32 / 28	Clindamycin	1- ≥ 256	≥256	≥256	57	11	36	17	2
iMLS_B	8 (2.7)	Erythromycin	2- ≥ 256	16	32	3	8	4	3	0
iMLS_B	3 / 5	Clindamycin	0.06-0.5	0.25	0.5	3	8	4	3	0
Total	295 (100)	Erythromycin	1- ≥ 256	64	256	110	106	264	241	3
Total	73 /222	Clindamycin	0.06-0.5	0.25	256

ISSN: 1471-2180