In vitro activity of mezlocillin and its therapeutic effect on respiratory tract infections

Antimicrobial activity of mezlocillin was tested and compared to those of Carbenicillin (CBPC) and Sulbenicillin (SBPC). Mezlocillin was more active against clinical isolates of Klebsiella pneumoniae than the two other penicillins tested. On the contrary, the drug revealed to be less active against clinicali solates of Pseudomonas aeruginosa as compared to CBPC and SBPC. Clinical evaluation of mezlocillin was made in 13 cases of respiratory tract infections. With drip intravenous infusion of 4 g a day of the drug, an excellent therapeutic effect was obtained in 5 cases. Good and fairly good response was observed in 6 cases and in 1 case respectively. In 1 case with secondary infection to lung cancer, the response was poor. Nine of 10 pathogenic organisms isolated, including 3 strains of gram-negative bacilli, were eliminated from the sputum during the treatment with the drug. In 1 case treated with the drug, eruption and fever developed on the 9th day of treatment, but the symptoms and signs disappeared promptly after withdrawal of the drug. No other serious adverse effect was observed during and after administration of the drug.