Figure 4.

Cell-wall active antibiotics can act synergistically or additively with PLA₂ to kill E. faecium. E. faecium strains 4 (a–c) and 6 (d–f) (10⁵/ml) were treated with ampicillin (16 μg/ml; a and d), cephalothin (32 μg/ml; b and e),vancomycin (30 μg/ml; c and f), or no antibiotic for 30 mi n in PHS buffered with 10 mM HEPES (pH 7.4) before treatment with 50 ng/ml (strain 4) or 500 ng/ml (strain 6) of purified rabbit AF group IIA PLA₂ at 37°C. At the indicated times, samples were removed to measure viability as described in Methods. The results represent the mean ± SEM of four experiments. Some error bars are masked by the symbols. (open squares) Bacteria alone; (closed squares) antibiotic + bacteria; (open circles) bacteria + PLA₂; (closed circles) antibiotic + bacteria + PLA₂.