[Bacteriostatic and bactericidal effect of cefotaxime combinations on Staphylococcus aureus assessed by FIC and...

Activity of cefotaxime associated with one of nine other antibiotics (amikacin, dibekacin, gentamicin, netilmicin, sisomicin, tobramycin, erythromycin, clindamycin, and chloramphenicol) was studied by a checkerboard method with determination of FIC and FBC-indices. Four S. aureus strains were used: one homogeneous methicillin-resistant strain (S1), one heterogeneous methicillin-resistant strain (S2), and two susceptible strains (S3 and S4). Strong synergism between cefotaxime and aminoglycosides was found only for S2, with no significant differences between aminoglycosides (index # 0.3). Cefotaxime and chloramphenicol showed synergistic or additive bacteriostatic activities and consistently antagonist bactericidal activities. Bactericidal activities of cefotaxime and erythromycin were likewise antagonistic, whereas cefotaxime and clindamycin occasionally exhibited in vitro synergism.