Table 4. Fractional Inhibitory Concentration Determination and Interaction Effect of Two Antimicrobial Agents (Antibiotics + Cell Free Supernatant) on the Pseudomonas aeruginosa PTCC 1430 ^a.

Combination of Two Compounds	MIC A (Alone) (μL/mL)	MIC B (Alone) (μL/mL)	MIC A (in the Presence of B) (μL/mL)	MIC B (in the Presence of A) (μL/mL)	Checkerboard FIC Index	Checkerboard Effect
L.Casei and Gentamicin	62.5	1	0.39	0.25	0.312	marked synergy
L. rhamnosus and Gentamicin	62.5	1	0.39	0.0625	0.124	marked synergy
L. casei and Amikacin	62.5	8	0.39	0.5	0.124	marked synergy
L. rhamnosus and Amikacin	62.5	8	0.39	4	0.56	weak synergy

^a Abbreviations: FIC, Fractional Inhibitory Concentration; and MIC, Minimum Inhibitory Concentrations.