The efficacy of thuricin CD, tigecycline, vancomycin, teicoplanin, rifampicin and nitazoxanide, independently and in paired combinations against Clostridium difficile biofilms and planktonic cells

Table 2 Fractional inhibitory concentration (FIC) values of various antimicrobial combinations against C. difficile

Antimicrobial combination/C. difficile strain	TCD-Teico^a ΣFIC	TCD-Tig^b ΣFIC	TCD-Rif^c ΣFIC	TCD-Nitaz^d ΣFIC	TCD-V^{e, i} ΣFIC
20291 R027	0.75 (PS)^f	1.0 (Ad)^g	1.0 (Ad)	1.01–2 (I)^h	1.01–2 (I)
Liv022 R106	1.01–2 (I)	1.01–2 (I)	1.01–2 (I)	1.01–2 (I)	1.0 (Ad)
TL178 R002	1.01–2 (I)	1.01–2 (I)	1.01–2 (I)	1.0 (Ad)	1.01–2 (I)
DPC6350	1.01–2 (I)	1.01–2 (I)	1.01–2 (I)	1.0 (Ad)	1.01–2 (I)
VPI10463	1.01–2 (I)	1.01–2 (I)	1.01–2 (I)	1.0 (Ad)	1.01–2 (I)

Antimicrobial combination effects are indicated in parentheses
PS partial synergy (0.5 ≤ FIC ≤ 0.75), Ad additive effects (0.75 ≤ FIC ≤ 1.0), I indifferent effects (1.01 ≤ FIC ≤ 2.0)
FIC indices of ^athuricin CD-teicoplanin, ^bthuricin CD-tigecycline, ^cthuricin CD-rifampicin ^dthuricin CD-nitazoxanide and ^ethuricin CD-vancomycin against C. difficile strains. ^fThuricin CD-vancomycin FIC values against strains 20291 R027, Liv022 R106 and TL178 R002 were already determined and reported in our previous study [7]

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