Treatment of serious Pseudomonas infections with azlocillin

Azlocillin is a semisynthetic acylureidopenicillin with increased activity against most strains of Pseudomonas aeruginosa. It was given as the sole antibacterial agent in the treatment of 21 patients with serious pulmonary, wound, bone or joint, or urinary tract infections, endocarditis, or malignant external otitis caused by Pseudomonas sp. In preliminary in vitro tests, azlocillin inhibited 90% of 36 clinical isolates, while carbenicillin and ticarcillin inhibited only 60% and 73%, respectively. Mean MIC of azlocillin against Ps. aeruginosa isolated from the 21 study patients was 9.8 mg/l; more than 50% of the strains were inhibited by a concentration of 6.25 mg/l. Intravenous administration of the antibiotic at a mean dosage of 17 g/day for 6 to 59 days resulted in an excellent or good clinical response in 90% (19) of the patients treated. Pseudomonas sp. was eliminated from the site of infection in 67% (14) of the patients. Azlocillin therapy was well tolerated; in only two patients, both of whom had penicillin-type rashes, was it necessary to discontinue therapy. Azlocillin was a safe and effective antimicrobial agent for the treatment of serious infections caused by strains of Pseudomonas sp., primarily Ps. aeruginosa.