1991 Volume 39 Issue 11 Pages 1029-1033
We determined the effect of NaCl on the antibacterial activities of arbekacin and other antibacterial compounds by bioassay. Addition of 4%(w/v) NaCl to the medium significantly decreased the antibacterial activities of arbekacin and other aminoglycoside antibiotics against methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA). The activities of β-lactam antibiotics were slightly decreased against S. aureus ATCC 25923 (MSSA) and decreased against S. aureus M-12 (MRSA) by the addition of 4% NaCl. Against S. aureus M-12 (MRSA) the activity of fosfomycin was also decreased by the addition of 4% NaCl. But the activities of vancomycin, minocycline, ofloxacin, sulfamethoxazole-trimethoprim (ST) and others showed almost no change against MSSA or MRSA in the 4% NaCl supplemented medium. We also determined the effect of the addition of 1%, 3%, 5%, 7% NaCl to the medium on the MICs of arbekacin and netilmicin. Against Escherichia coli and other Gram-negative bacteria in addition to S. aureus, the MICs of arbekacin and netilmicin rose as the concentration of additional NaCl increased. Our results showed that the effect of NaCl on antibacterial activity varied with the kind of antibacterial compound used. The antibacterial activities of arbekacin and other aminoglycoside antibiotics were decreased by adding NaCl to the medium.
