In vitro antibacterial activity of cefotaxime and desacetylcefotaxime, alone or in combination, against gram-positive cocci.

The in vitro activity of cefotaxime and desacetylcefotaxime against Staphylococcus aureus, Staph. epidermidis and Streptococcus pyogenes was investigated. Synergy studies were performed using time-kill curves and the chequerboard test. The time-kill curves were performed on five strains each of Staph. aureus, Staph. epidermidis and Strep. pyogenes; cefotaxime and desacetylcefotaxime were tested alone or in combination at MIC and sub-MIC values. The chequerboard test was performed in microtitre plates on ten strains each of Staph. aureus, Staph. epidermidis and Strep. pyogenes: the results were interpreted by the fractional inhibitory concentration index. In some cases both methods showed synergistic interaction against the staphylococci tested. Indifference was observed against Strep. pyogenes.