Combination effect of azthreonam with four aminoglycosides on nosocomial gram-positive cocci and non-fermenting gram-negative bacteria.

The inhibitory combination effect of azthreonam with gentamicin, tobramycin, amikacin and netilmicin respectively against 50 non-fermenting gram-negative rods and 30 gram-positive cocci was compared using the checkerboard agar dilution technique. On average 49.5% of all non-fermenting strains were inhibited by additive, and 48.5% by synergistic azthreonam-aminoglycoside combinations, but only 4.5% of the gram-positive cocci were inhibited by synergistic combinations. No antagonism occurred. No significant differences could be found between the effects of the respective azthreonam-aminoglycoside combinations.