TABLE 4.

Minimum biofilm eradication concentration and fractional bactericidal concentration index against biofilm (FBCI_b) values of polymyxin B and EDTA, alone and in combination against biofilms of Staphylococcus aureus ATCC 6538 and Pseudomonas aeruginosa ATCC 27853^a

	PMB MBECa (µg/mL) (n)	PMB MBECc (µg/mL) (n)	P value	EDTA MBECa (mg/mL) (n)	EDTA MBECc (mg/mL) (n)	P value	FBCIb
S. aureus	16,384 (4,096–32,768) (15)			>135 (67.5 to >135) (11)
P. aeruginosa	32 (8–64) (16)	8 (4–32) (16)	<0.0001	135 (13)	16.9 (8.4–67.5) (16)	<0.0001	0.38 (0.19–1.1)

^a All values are expressed as median (range). If there was no variation between replicates, no range is given. P values were determined by the Mann-Whitney U test. PMB: polymyxin B. MBEC_a: minimum biofilm eradication concentration of the antimicrobial tested alone. MBEC_c: minimum biofilm eradication concentration of the antimicrobial tested in combination. n: number of replicates.