Table 1. Quadruple synergistic combinations among rifampicin, clarithromycin, amoxicillin and clavulanate against M. ulcerans clinical isolates.

		MIC (μg/mL) alone			MICsyn (μg/mL) at the MOCC			Fold-Reduction at the MOCC
Clinical isolate	Geographical origin	RIF	AMX	CLA	RIF	AMX	CLA	RIF	AMX	CLA	Quad FICI
ITM 063846	Benin	0.025	>32	0.125	0.0031	1	0.003	8	64	40	0.20
ITM 070290	China	0.5	>32	1	0.0016	0.063	0.05	313	1024	20	0.09
ITM 83720	Mexico	0.1	16	0.125	0.0063	0.063	0.003	16	256	40	0.13
ITM 941327	Australia	0.002	>32	0.5	0.0004	0.031	0.025	5	2065	20	0.29
ITM C05142	Australia	0.1	16	0.125	0.0016	0.063	0.0031	64	256	40	0.08
ITM C05143	Mexico	0.05	16	0.25	0.0008	4	0.0031	64	4	80	0.32
ITM C05150	DR Congo	0.02	>32	0.25	0.0013	0.063	0.0031	16	1024	80	0.12
ITM C08756	Japan	0.2	>32	0.25	0.0016	0.250	0.0125	128	256	20	0.10
ITM M000932	Australia	0.05	>32	0.063	0.0001	0.125	0.0031	640	256	20	0.09

Clavulanate was added to the quadruple combination at a fixed dose of 5 μg/mL. For FICI calculations, its MIC was considered as 128 μg/mL. RIF, rifampicin; AMX, amoxicillin; CLA, clarithromycin; MOCC, Most Optimal Combinatorial Concentration; Fold-Reduction, MIC/MIC_syn; FICI ≤0.5 indicates synergy.