TABLE 1.

Capsular type, CrrB amino acid substitutions, MICs, and β-lactamases of colistin-resistant strains

Strain	Capsular typea	Amino acid at CrrB positionb:						Colistin MIC (μg/ml)a	Presence in strainc
		10	31	140	141	151	195		TEM-1	TEM-116	SHV-1a	SHV-31	CTX-M Group 2	CTX-M Group 9	DHA
Col4	K64				Ile			>2,048	+		+		+	+	+
Col7	K64					Ser		1,024	+		+		+		+
Col20	K64				Ile			2,048		+	+		+	+
Col21	K64	Leu						512	+		+		+	+	+
Col22	K64						Asn	2,048	+		+		+	+	+
Col36	K64			Arg				2,048	+		+			+	+
Col44	K64		His					512	+		+			+
Col28	K54	Leu						>2,048	NAd	NA	NA	NA	NA	NA	NA

^aCapsular type and MICs of colistin were determined in our recent study (8).

^bPositions of amino acid substitutions in CrrB.

^c+, present. According to previous studies (8, 34), β-lactamase was amplified by PCR. The PCR products were sequenced, and β-lactamases were classified by NCBI Blast.

^dNA, the β-lactamase(s) of strain Col28 was not available.