Blood samples were collected 1 h (Cmax) after dosing and serum killing rates were determined against a serotype 3 penicillin (PEN) Á/ciprofloxacin (CIP) susceptible strain (S3) (MICs of 0.03, 1, 0.015 and 0.06 mg/l for PEN, CIP, GEM and TRO) and a serotype 9 PEN Á/CIP resistant strain (S9) (MICs of 2, 4, 0.03 and 0.25 mg/l for PEN, CIP, GEM and TRO).