Antimicrobial Susceptibility among Colistin, Sulbactam, and Fosfomycin and a Synergism Study of Colistin in Combination with Sulbactam or Fosfomycin against Clinical Isolates of Carbapenem-Resistant Acinetobacter baumannii

Table 1

Minimum inhibitory concentration (MIC) determination by E-test and susceptibility interpretation of colistin, sulbactam, and fosfomycin against carbapenem-resistant A. baumannii isolates.

Strains	Specimen	REP-PCR group	MIC (mg/L) determination
			Colistin; (interpretation	Sulbactam; (interpretation	Fosfomycin; (interpretation
AB 1	Blood	A	2 (S)	96 (R)	192 (R)
AB 2	Pus	A	1.5 (S)	4 (S)	192 (R)
AB 3	Blood	B	2 (S)	24 (R)	128 (R)
AB 4	Femur tissue	A	1.5 (S)	24 (R)	96 (R)
AB 5	Sputum	C	2 (S)	2 (S)	64 (R)
AB 6	Sputum	A	1.5 (S)	6 (S)	128 (R)
AB 7	Sputum	A	1.5 (S)	8 (I)	256 (R)
AB 8	Sputum	D	1.5 (S)	8 (I)	96 (R)
AB 9	Sputum	E	1 (S)	12 (I)	96 (R)
AB 10	Sputum	F	0.75 (S)	16 (R)	192 (R)
AB 11	Sputum	G	1 (S)	16 (R)	256 (R)
AB 12	Pus	H	1.5 (S)	96 (R)	256 (R)
AB 13	Sputum	A	1.5 (S)	12 (I)	192 (R)
AB 14	Sputum	A	1.5 (S)	8 (I)	128 (R)
AB 15	Urine	A	1.5 (S)	16 (R)	128 (R)

Breakpoint criteria as follows: : susceptible; S, ≤2 mg/L; resistant; R, >4 mg/L, : susceptible; S, ≤4 mg/L; intermediate; I, 8 mg/L; resistant; R, ≥16 mg/L and : susceptible; S, ≤32 mg/L; resistant; R, >32 mg/L.