. 2016 Feb 5;82(4):1060–1068. doi: 10.1128/AEM.03280-15

TABLE 3.

Characteristics of ENR-resistant clones obtained in vitro under increased selective pressure, point mutations in QRDRs, and MIC values

Clone^a	ENR concn (μg/ml)^b	Mutation distribution^c			Mutation at indicated position						MIC (μg/ml)^d
		Mutation distribution^c			GyrA			ParC			MIC (μg/ml)^d
		2nd step	3rd step	4th step	Gly81	Ser83	Glu87	Ser80	Asp84	Thr98	ENR	DAN	MAR
PG45 (GT1 [ST1], GyrB Asp362, 0.25)	0.5	2/7						Ile			4	8	8
	1		18/18					Ile			4	8	16
	2			3/3				Ile			8	8	16
	0.5	4/7							Tyr		1	2	2
	1		1/7			Tyr			Tyr		4	8	8
	1		2/7			Lys			Tyr		4	8	4
	1		1/7			Phe			Tyr		4	8	8
	1		3/7*		Asp				Tyr		4	8	4
	2			1/3	Asn				Tyr		4	8	4
	2			2/3	Asp				Tyr		4	4	4
	0.5	1/7									1	2	1
	1		1/4*			Tyr					2	2	4
	1		1/4*			Phe					1	2	2
	1		1/4			Tyr			Tyr		4	8	8
	1		1/4			Phe			Tyr		4	8	8
	2			1/1		Tyr		Ile			16	16	16
	2			2/2		Phe			Tyr		16	16	16
15762 (GT4 [ST2], GyrB Asn362, 0.25)	0.5	2/7					Lys				ND	ND	ND
	0.5	1/7									0.5	1	2
	0.5	4/7*									0.5	1	2
	1		5/8			Tyr					ND	ND	ND
	1		1/8			Phe					ND	ND	ND
	1		1/8				Lys				ND	ND	ND
	1		1/8								ND	ND	ND
15527 (GT2 [ST3], GyrB Asn362, 4)	1	12/12				Phe			Asn		8	8	16
	2		36/36			Phe			Asn		ND	ND	ND
	8–16			5/6		Phe			Asn		16	8	16
	8–16			1/6		Phe			Lys		32	8	16
15527 (GT3 [ST3], GyrB Asn362, 4)	1	12/12				Phe			Asn	Arg	8	8	16
	2		36/36			Phe			Asn	Arg	ND	ND	ND
	8–16			1/2		Phe			Asn	Arg	16	8	16
	8–16			1/2		Phe			Lys	Arg	16	16	32
8619 (GT5 [ST3], GyrB Asn362, 1)^e	0.5	22/22				Phe					1	2	2
	1		3/4			Phe					ND	ND	ND
	1		1/4*			Phe		Ile			32	16	>64
	2			2/2		Phe		Ile			32	16	>64
	0.5	22/22				Phe					1	2	2
	1		12/28			Phe					ND	ND	ND
	1		2/28			Phe			Gly		8	8	16
	1		4/28*			Phe			Asn		8	8	16
	1		10/28*			Phe			Tyr		8	8	16
	2			2/2		Phe			Asn		8	8	16
	2			2/2		Phe			Tyr		8	8	16

Clones are presented by the name of the parental strain, the subtype, the GyrB phenotype, and the enrofloxacin MIC (μg/ml) at the 1st selection step.

Concentration of ENR used to select the different resistant clones during individual passages.

Asterisks indicate clones used to perform the following selection step.

MICs were evaluated on at least one clone of the selected genotype. When no clone was available in broth culture, MIC assays were not performed. ND, not done.

Step 3 was performed using two different clones (same genotype) randomly selected at step 2.