Septicaemia caused by an Enterobacter cloacae strain varying in resistance against cephalosporins.

Enterobacter cloacae, sensitive to third-generation cephalosporins (cefotaxime and ceftazidime), was isolated from the stoma of a patient with leukaemia. One month later, he developed a fatal septicaemia, caused by an identical strain isolated from blood cultures. He had been treated with several antibacterial agents, including cefotaxime. The blood culture strain seemed to be a mixture of four variants with different resistance patterns to cefotaxime and ceftazidime. One variant was extremely sensitive to third-generation cephalosporins, one was completely resistant, and two showed variations in zone diameter within sensitivity group 2, both for cefotaxime and ceftazidime. Minimal inhibitory concentration (MIC) studies also showed different resistance patterns between the four variants. Similar variants were found when the stoma isolate was further investigated.