Mechanism of Reduced Susceptibility to Fosfomycin in Escherichia coli Clinical Isolates

Table 3

Characteristics of E. coli strains used in the study.

Strain	Specimen	Sero-; group	Phylo-; genetic group	MLST	MIC(μg/mL)			Growth on; M9 agar supplemented with:		uhpT expression induced by G6P	Amino acid residue alternations in proteins encoded by glpT, ptsI, cyaA, murA, uhpA, and uhpT genes
					G6P −	G6P +	G6P+; cAMP+	G3P	G6P		cyaA	glpT	murA	ptsI	uhpA	uhpT
SRE257	Urine	O1	B2	95	1024	1024	1024	+	−	1.24	—	—	—	Val399Leu	163~188 deletion	—
SRE91	Aspiration tube	O1	D	648	128	128	32	−	−	3.78	—	155~158 deletion; Phe176Leu	—	—	Thr3Ala	—
SRE49	Urine	O25b:H4	B2	131	128	128	128	+	−	NT	His716Leu	—	—	Lys410Arg	ND	ND
SRE54	Urine	O25b:H4	B2	131	64	64	64	+	−	1.59	His716Leu	—	—	Ala443Thr; Gly452Asp	—	—
SRE237	Urine	O25b:H4	B2	131	64	64	64	+	−	1.59	His716Leu	—	—	—	—	—
SRE29	Urine	O25b:H4	B2	131	32	32	32	+	+	1226.22	—	—	—	—	—	—
SRE252	Urine	O25a	D	73	32	32	4	−	−	3.68	ND	Ile171Thr	—	Lys145Asn	—	—
SRE280	Ascites	O12	D	1486	32	32	32	+	−	0.56	Ser142Asn	—	—	—	—	—
SRE18	Urine	ND	D	405	16	16	16	+	−	2.22	—	—	—	—	Met1Ile	—
SRE253	Urine	O18	B2	95	8	8	8	−	−	198.09	His716Leu	—	—	—	—	—
SRE40	Decubitus	O25a	D	501	32	0.5	NT	+	+	284.05
SRE41	Catheter urine	O1	D	648	8	0.5	NT	+	+	328.56
SRE110	Catheter urine	O25b:H4	B2	131	8	0.5	NT	+	+	190.02
SRE205	Urine	ND	A	131	8	0.5	NT	+	+	734.19
SRE227	Pus	O1	B2	95	8	0.5	NT	+	+	247.28
SRE30	Urine	O1	D	648	8	0.25	NT	+	+	719.08
ATCC 25922		NT	NT		32	0.5	NT	+	+	308.69

FOM MICs were determined in the presence (+) or absence (−) of glucose-6-phosphate (G6P) and/or cAMP.
E. coli cells were incubated in M9 minimum salt solution in the presence or absence of G6P. The uhpT mRNA levels were determined by real-time RT-PCR, and the data were normalized to rpoD mRNA levels. Induction of uhpT expression by G6P was calculated by dividing the uhpT mRNA level in the presence of G6P by the uhpT mRNA level in the absence of G6P.
Amino acid mutations found only in strains with reduced FOM susceptibility (MIC ≥ 8 μg/mL) compared with strains with FOM MIC < 1 μg/mL.
ND: not detected. NT: not tested.