Clinical experience with azlocillin

Mezlocillin and azlocillin are new semi-synthetic ureidopenicillins. Both possess a broad spectrum of activity in vitro. Potency of activity against Gram-positive and fastidious Gram-negative organisms and against obligate anaerobes is comparable. Mezlocillin is more active against Enterobacteriaceae while azlocillin is more potent against Pseudomonas species. Although direct comparative studies in serious Gram-negative bacillary infections have not been performed, it would appear prudent to administer mezlocillin in disease due to Enterobacteriaceae, and to prescribe azlocillin preferentially when the aetiological agent is presumed or known to be Pseudomonas. The use of azlocillin to treat serious infections with Ps. aeruginosa is described here. A variety of clinical and laboratory observations may permit implication of Pseudomonas in the aetiology of specific infections.