Clinical consequences of development of resistance to third generation cephalosporins.

Eighteen patients are described in whom initially sensitive microorganisms were replaced by resistant isolates during administration of ceftriaxone (n = 8), cefoperazone (n = 5), moxalactam (n = 4), cefotaxime (n = 2) or ceftazidime (n = 1), despite combination with aminoglycosides. All patients had documented gram-negative infections; in 12 patients underlying haematological diseases were present. Resistant strains of Enterobacter cloacae (14), Serratia marcescens (4), Klebsiella oxytoca (3), Pseudomonas aeruginosa (2) and Citrobacter freundii (2) emerged within 2 to 19 (mean 9) days after the beginning of treatment. In 12 patients relapse or secondary infections occurred. Seven of the patients with haematological disorders died. Resistance development was seen in 8 of 29 patients on ceftriaxone and 4 of 10 patients on moxalactam during prospective evaluations; the other drugs were used sporadically. Thus, selection of resistant bacteria is relatively frequent and may have serious clinical consequences in patients with impaired host-defense mechanisms.