Ciclacillin is produced by the strain of Semi-synthetic broad-spectrum penicillin. The antibacterial activity of cyclociline against 101 strains of Escherichia coli, 50 strains of Proteus and 59 strains of Staphylococcus aureus was lower than that of ampicillin and carboxpicillin. The blood concentration is higher than ampicillin, but excretion is fast.