Bacteraemia with Escherichia coli in diabetic patients. Studies on bacterial virulence and host factors

A total of 70 episodes of E. coli bacteraemia occurred in 10 patients with insulin-dependent, and 54 patients with non-insulin-dependent diabetes mellitus. The bacteraemic strains were tested for aerobactin mediated iron uptake, a property that is regarded as a virulence factor of E. coli. Aerobactin mediated iron uptake was present in 60% of the isolated strains from the diabetic patients. A similar prevalence, 54%, was noted in E. coli from a control group of non-diabetic patients with bacteraemia. The prevalence of aerobactin positive strains, isolated from both diabetic and non-diabetic patients, was significantly higher than in faecal E. coli strains (39%) obtained from healthy subjects. In E. coli from diabetic patients, another bacterial virulence factor, P-fimbriae, was present on 62% of the aerobactin positive strains but only on 33% of strains lacking aerobactin mediated iron uptake. No examined host factors in the diabetic patients, such as age, sex, duration of diabetes, serum creatinine and presence of proteinuria, influenced the prevalence of aerobactin mediated iron uptake. In conclusion, bacterial virulence mediated by the aerobactin system occurs as frequently in diabetic as in non-diabetic patients with E. coli bacteraemia, and furthermore seems to co-exist with P-fimbriation.