Table 1. Results of time-kill assay and bactericidality against two-drug combinations of linalool and colistin of 10 MDR and 41 XDR clinical isolates of A. baumannii

Ann Clin Microbiol 2020;23:11-20. Evaluation of Synergistic Effect of Combined Treatment with Linalool and Colistin on Multidrug-Resistant Acinetobacter baumannii to Expand Candidate for Therapeutic Option

Table 1. Results of time-kill assay and bactericidality against two-drug combinations of linalool and colistin of 10 MDR and 41 XDR clinical isolates of A. baumannii

Group	Isolate	Log10(VCC of combination/VCC of MASA) of 24 hr	Log10(VCC of 24 hr) – Log10(VCC of 0 hr)			Synergy criteria 1‡	Synergy criteria 2§	MIC	MIC	Category	Bactericidality∥
Group	Isolate	Log10(VCC of combination/VCC of MASA) of 24 hr	LNL*	CST†	LNL* + CST†	Synergy criteria 1‡	Synergy criteria 2§	LNL	CST	CST	LNL*	CST†	LNL* + CST†
MDR	89-92	-5.2	3.8	3.7	-1.4	S	I ¶	4.0	8.0	R	N	N	N
	171-84	-6.1	0.1	2.9	-5.8	S	S	16.0	2.0	S	N	N	B
	172-91	-3.4	0.8	0.8	-2.5	S	S	16.0	2.0	S	N	N	N
	172-99	-5.1	-1.1	2.0	-6.2	S	S	4.0	1.0	S	N	N	B
	174-99	-8.1	2.9	3.1	-5.2	S	S	16.0	16.0	R	N	N	B
	180-82	-2.7	-3.4	0.1	-5.9	S	S	16.0	0.5	S	B	N	B
	181-67	-9.5	1.9	1.7	-5.3	S	S	32.0	0.5	S	N	N	B
	186-88	-5.0	-0.3	0.9	-5.2	S	S	16.0	2.0	S	N	N	B
	191-19	-8.2	3.1	4.2	-5.0	S	S	8.0	2.0	S	N	N	B
	200-92	-7.4	2.1	4.1	-5.1	S	S	8.0	2.0	S	N	N	B
XDR	69-84	-5.2	2.6	3.9	-2.5	S	S	4.0	8.0	R	N	N	N
	99-73	-6.1	0.2	0.3	-5.3	S	S	8.0	8.0	R	N	N	B
	111-27	-6.2	0.9	2.8	-5.3	S	S	32.0	2.0	S	N	N	B
	130-33	-4.1	1.8	1.9	-2.3	S	S	4.0	16.0	R	N	N	N
	139-27	-4.0	-1.3	3.1	-5.3	S	S	16.0	2.0	S	N	N	B
	148-33	-4.4	-1.4	1.3	-5.8	S	S	8.0	8.0	R	N	N	B
	150-94	-5.4	2.2	2.1	-3.2	S	S	8.0	2.0	S	N	N	B
	155-24	-2.7	1.8	3.6	-2.7	S	S	4.0	2.0	S	N	N	N
	158-46	-4.0	-1.9	-1.9	-5.9	S	S	8.0	2.0	S	N	N	B
	158-86	-7.2	2.2	3.2	-5.0	S	S	8.0	1.0	S	N	N	B
	158-87	-5.8	0.7	4.2	-5.2	S	S	8.0	8.0	R	N	N	B
	159-86	-7.0	1.0	3.2	-6.0	S	S	8.0	0.3	S	N	N	B
	160-14	-2.4	-0.2	-0.3	-2.6	S	S	4.0	16.0	R	N	N	N
	160-15	-7.0	1.7	1.7	-5.2	S	S	16.0	1.0	S	N	N	B
	160-68	-6.0	0.7	3.9	-4.9	S	S	16.0	8.0	R	N	N	B
	160-92	-6.2	0.9	3.8	-5.3	S	S	16.0	4.0	R	N	N	B
	160-93	-3.2	-3.0	1.9	-6.0	S	S	8.0	8.0	R	N	N	B
	162-83	-6.0	-0.2	2.3	-5.9	S	S	16.0	0.5	S	N	N	B
	162-88	-3.1	0.7	3.8	-2.3	S	S	4.0	8.0	R	N	N	N
	163-71	-3.6	4.4	4.3	0.8	S	I	2.0	8.0	R	N	N	N
	163-72	-1.9	-0.5	0.7	-2.5	I	I	4.0	8.0	R	N	N	N
	163-77	-7.3	2.2	2.0	-5.1	S	S	16.0	4.0	R	N	N	B
	164-35	-4.3	1.8	1.9	-2.3	S	S	4.0	2.0	S	N	N	N
	164-62	-5.8	0.6	4.0	-5.0	S	S	8.0	2.0	S	N	N	B
	165-41	-3.3	0.8	1.7	-2.4	S	S	4.0	8.0	R	N	N	N
	165-83	-8.2	2.9	2.9	-5.2	S	S	16.0	8.0	R	N	N	B
	165-83	-7.2	1.8	2.8	-5.2	S	S	16.0	8.0	R	N	N	B
	166-13	-6.4	2.0	2.9	-4.4	S	S	16.0	0.5	S	N	N	B
	166-24	-6.2	0.9	3.0	-5.3	S	S	8.0	1.0	S	N	N	B
	166-61	-8.3	3.5	4.3	-4.8	S	S	32.0	1.0	S	N	N	B
	172-89	-8.2	2.4	2.3	-6.0	S	S	8.0	2.0	S	N	N	B
	177-35	-5.2	2.9	2.9	-2.1	S	S	4.0	2.0	S	N	N	N
	189-52	-7.2	2.1	3.2	-4.9	S	S	8.0	2.0	S	N	N	B
	189-97	-7.1	1.8	1.9	-5.2	S	S	16.0	2.0	S	N	N	B
	200-19	-4.3	2.0	2.0	-2.2	S	S	8.0	2.0	S	N	N	N
	218-62	-6.0	0.8	0.6	-5.2	S	S	16.0	1.0	S	N	N	B
	219-12	-5.3	2.1	1.9	-3.2	S	S	16.0	1.0	S	N	N	B
	219-56	-6.9	1.7	3.0	-5.0	S	S	16.0	1.0	S	N	N	B
	219-67	-0.4	-4.0	4.0	-4.4	I	I	16.0	1.0	S	B	N	B
	222-23	-2.8	-3.2	1.1	-6.1	S	S	8.0	1.0	S	B	N	B
	230-54	-5.0	-1.1	-1.0	-6.1	S	S	8.0	1.0	S	N	N	B

*Linalool 1/4 MIC; †Colistin 2 μg/mL; ‡≥2 log₁₀ CFU/mL reduction with the combination compared with the most active single agent of 24hr; §≥2 log₁₀ CFU/mL reduction with the combination compared with the most active single agent and ≥2 log₁₀ CFU/mL reduction below the initial inoculum at 24 hr; ∥≥3 log₁₀ CFU/mL reduction compared with the initial inoculums; ¶ <2 log₁₀ change in CFU/mL at 24 hr with the combination compared with the most active single agent Abbreviation: MIC, minimum inhibitory concentration; LNL, Linalool; CST, Colistin; B, bactericidal; N, non-bactericidal; MDR, multidrug-resistant; XDR, extensively drug-resistant; S, synergy; I, Indifference; VCC, viable cell count, MASA, most active single agent.