Table 6. Effects of acetylsalicylic acid and its metabolites on the susceptibility of Gram-negative clinical strains (12 isolates of each species) to quinolones in the presence or absence of PAβN.

Bacteria	Agent MICs range [mg/L]	No. of strains with ≥4-fold (only 2-fold) increase in antimicrobial agent MICs in the presence of NSAID ± PAβN
		At+ PAβN	At+Aca	At+Ac+ PAβNb	At+SNaa	At+SNa+ PAβNb	At+Sa	At+S+ PAβNb
E. coli	ofloxacin (1–64)	12 (0)	0 (6)	0 (5)	1 (7)	0 (9)	2 (8)	0 (12)
K. pneumoniae	ofloxacin (8–32)	12 (0)	0 (0)	0 (3)	0 (0)	0 (1)	0 (0)	0 (3)
P. aeruginosa	ofloxacin (2–128)	12 (0)	0 (0)	0 (7)	0 (0)	0 (7)	0 (0)	0 (11)
S. maltophilia	ofloxacin (1–8)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)
	nalidixic acid (8–32)	12 (0)	0 (2)	0 (0)	0 (7)	0 (0)	0 (7)	0 (0)

At, antimicrobial agent; PAβN, efflux pump inhibitor; Ac, acetylsalicylic acid 1 mM; SNa, sodium salicylate 1 mM; S, salicylic acid 1 mM.

^aAt least a 4-fold (only 2-fold) increase in the MIC of the antimicrobial agent in the presence of NSAID, when compared to the MIC of antimicrobial agent alone.

^bAt least a 4-fold (only 2-fold) increase in the MIC of the antimicrobial agent in the presence of NSAID and PAβN, when compared to the MIC of the antimicrobial agent in the presence of only PAβN.