Metformin as a Potential Adjuvant Antimicrobial Agent Against Multidrug Resistant Bacteria

Figures & data

Table 1 The MIC and the FIC of Metformin Alone and in Combination Against the Tested Bacterial Strains

Bacterial Strain	Antimicrobial Agent (A.b.) (μM)	MIC Alone (A.b.) (μM)	MIC in Combination (A.b.) (μM)	% Reduction in MIC (A.b.)	MIC Alone for Metformin (μM)	MIC in Combination For Metformin (μM)	% Reduction in MIC (Peptide)	FICI (μM)	Synergism
2.5/25 Staph 33,591	Levofloxacin	10	1	90%	>500	25	90%	0.15	Synergistic
	Chloramphenicol	130	12.5	90%	>500	12.5	97%	0.12	Synergistic
	Ampicillin	85	6.5	92%	>500	25	90%	0.126	Synergistic
	Rifampicin	0.04	0.025	37%	>500	25	90%	0.67	Additive
	Doxycycline	40	2.5	93%	>500	12.5	97%	0.112	Synergistic
P. aeruginosa R.S. (BAA-2114)	Levofloxacin	12	3	75%	>500	12.5	95%	0.275	Synergistic
	Chloramphenicol	200	12.5	93%	>500	12.5	95%	0.08	Synergistic
	Ampicillin	>500	50	90%	>500	12.5	85%	0.12	Synergistic
	Rifampicin	50	12	76%	>500	12.5	90%	0.265	Synergistic
	Doxycycline	60	12.5	79%	>500	12.5	90%	0.12	Synergistic

Figure 1 The cytotoxicity of combinations of metformin and tested antibiotics in VERO cell line expressed as cell viability percentage, A. Metformin + Doxycycline, B. Metformin + Levofloxacin, C. Metformin + Ampicillin, and D. Metformin + Rifampicin. Dose of combination is expressed as multiples of MIC of the combination of metformin and the tested antibiotic. Points between the two stars (*) are significantly different from baseline (zero dose) cell viability using unpaired t-test and P<0.05. Values are expressed as Mean±SD.