Table 2.

Distribution of different fluoroquinolone MICs in streptococcus and enterococcus strains and amino acid substitutions responsible for elevated fluoroquinolone MICs^a

Organism and isolate no.	MIC (mg/liter)								Amino acid substitution(s)
	OZN		MXF		LVX		CIP
	−R	+R	−R	+R	−R	+R	−R	+R	GyrA	ParC
S. pyogenes (QS)
017	0.03	0.015	0.25	0.25	0.5	0.5	0.5	0.12	NM	NM
117	0.03	0.015	0.12	0.12	0.5	0.5	0.5	0.12	NM	NM
39	0.03	0.015	0.12	0.12	0.5	0.12	0.5	0.12	NM	NM
016	0.12	0.12	0.12	0.06	0.5	0.12	2	1	NM	NM
S. pyogenes (QR)
165	0.12	0.12	1	0.06	16	0.06	4	2	NM	NM1
170	0.12	0.12	1	1	8	8	8	8	NM	NM
168	0.25	0.12	2	0.06	8	0.015	4	2	Ser81Phe	NM
166	0.25	0.25	4	4	16	8	16	16	Ser81Phe	Ser79Phe
S. agalactiae (QS)
283	0.03	0.03	0.25	0.25	1	1	0.5	0.25	NM	NM
536	0.03	0.03	0.25	0.25	1	1	1	0.25	NM	NM
420	0.03	0.03	0.25	0.25	1	1	0.5	0.25	NM	NM
146	0.06	0.03	0.25	0.25	2	1	0.25	0.25	NM	NM
S. agalactiae (QR)
159	0.5	0.5	4	4	32	32	64	32	NM	Ser79Phe
155	0.5	0.5	4	4	32	32	64	32	Ser81Leu	Ser79Phe
156	1	1	8	8	64	64	64	32	Ser81Leu	Ser79Phe
157	1	1	8	8	64	64	128	32	Ser81Leu	Ser79Phe
E. faecium (QS)
29.01	0.06	0.06	0.5	0.5	2	2	1	1	NM	Ser80Ile
897	0.25	0.25	0.5	0.5	2	2	1	1	NM	Ser80Ile
E. faecium (QR)
531	0.5	0.5	2	2	4	2	8	8	NM	Ser80Ile
454	2	2	32	32	128	64	512	512	Ser83Ile	Ser80Ile
075	4	4	64	32	128	32	512	512	Ser83Ile	Ser80Ile
59.02	4	4	64	32	128	64	256	256	Ser83Ile	Ser80Ile

^aR, reserpine; QS, quinolone susceptible; QR, quinolone resistant; NM, no mutations in the gyrA and parC genes.