A comparison of cefonicid with other beta-lactams regarding the effect of human and mouse sera on antibacterial activity.

The effect of the addition of 50% human or mouse serum on the antibacterial activity of cefonicid, three first generation cephalosporins and ampicillin was studied. Human serum added to the test system considerably reduced the activity of cefonicid against Staphylococcus aureus and Staphylococcus epidermidis strains, and to a lesser degree against Proteus mirabilis, Escherichia coli and Klebsiella pneumoniae strains. Human serum also reduced, albeit to a lesser extent, the activities of cephalothin, cefazolin, and ampicillin, whereas it increased the activity of cephaloridine. In contrast, mouse serum did not or only insignificantly reduced the activity of cefonicid against some of the bacterial isolates; this is reflected in the excellent protective effect of cefonicid in experimental mouse infections.