Table 2. Fractional inhibitory concentration index (FICi) for semapimod in combination with rifampicin.

Growth inhibition checkerboard assays were performed where an overnight culture was diluted 1 in 10,000 into fresh LB broth, and semapimod and rifampicin were added simultaneously in two-fold gradients to create a concentration checkerboard. An FICi value of less than 0.50 indicates synergy, an FICi value between 0.50 to 4.00 indicates indifference, and an FICi value greater than 4.00 indicates antagonism.

Species	FICi
E. coli BW25113	0.18
P. aeruginosa PAO1	2.00
K. pneumoniae ATCC 13883	0.19
E. coli ATCC 25922	0.06
A. baumannii ATCC 17978	0.08
E. coli BW25113 carrying mcr-1	0.18