Table 1. Characteristics of the mcr-4 positive strains analysed in this study, Italy 2013, Spain and Belgium, 2015 to 2016 (n = 4), and their transformants and conjugants.

Strain	Country	MLST	Plasmid content	Plasmid-mediated colistin resistance	Additional resistance genes	Colistin MIC mg/L
R3445 *Salmonella enterica*	Italy	34	ColE10, ColRNAI_34, ColRNAI_36, ColRNAI_38, ColRNAI_46	mcr-4	bla _TEM-1B, strA, strB, sul2, tet(B)	8
3445T (transformant in DH5-α)			ColE10	mcr-4		2
DH5-α						0.25
R4287 *Escherichia coli*	Spain	10 (CC10)	I1, I2, FII, FIB, FIC, HI2, Col156, ColRNAI_34, ColE10	mcr-4	bla _TEM-1B, aph(4)-1a, aph(3’)-1c, aac(3)-IVa, aac(3)-IIa, strA, aadA1, floR, catA1, sul2, sul1, tet(B), dfrA1, mph(A), erm(B), mphB	8
4287C (conjugant in CSH26 Rif^R)			ColE10, I2	mcr-4		4
CSH26 Rif^R						0.25
R4280 *E. coli*	Belgium	10 (CC10)	I1, FII, FIB, FIC, HI2, Col(MG828), ColRNAI_34, ColE10	mcr-4	bla _TEM-1B, aph4–1a, aac(3)-IVa, strB, aadA1, floR, catA1, sul1, tet(B), dfrA1, mph(B)	8
R4278 *E. coli*	Belgium	7029	I1, X1, FII(pCoo), ColE10	mcr-4	bla _TEM-1B, strA, strB, aadA1, sul2, sul1, tet(A), dfrA1	16

MIC: minimum inhibitory concentration; MLST: multilocus sequence typing.