The emergence of resistance and the therapy of septicaemia.

There were 658 positive blood cultures in St. Thomas' Hospital during 1982-1984, from which 301 Enterobacteriaceae were isolated. Most were of species that do not usually produce inducible class I beta-lactamases but 39 of the isolates were of species that do. Many of these strains were resistant to the older cephalosporins but resistance to cefuroxime was uncommon and resistance to ceftazidime or cefotaxime was confined to five isolates of Enterobacter cloacae (four of which were from patients who had been previously treated with beta-lactams). In only two cases did initially cefuroxime-sensitive strains unambiguously develop resistance during treatment (one strain each of Enterobacter aerogenes and Citrobacter freundii--both treated with amoxycillin).