Escherichia coli populations from diabetic and non-diabetic patients with bacteraemia and faecal samples from healthy subjects--a comparative study.

Biochemical reactions, using the PhP-EC system of biochemical fingerprinting, were evaluated in order to group strains into different clusters and to investigate whether a biochemical typing system may be used to distinguish between randomly selected Escherichia coli strains obtained from bacteraemic patients and healthy controls. Fifty epidemiologically unrelated strains isolated from blood of non-diabetic patients and 46 faecal control strains were studied. Separately, 70 E. coli strains from 64 diabetic patients with bacteraemia were investigated. Diversity index was 0.977, 0.969 and 0.941 respectively. The strains were clustered at a similarity level of 0.95. The bacteraemic and control strains were subdivided into 14 different clusters with 2-12 strains each and 40 'outliers'. The largest cluster was dominated by bacteraemic strains (9/12, 75%). Two other clusters were dominated by control strains. In the remaining groups blood and faecal isolates were evenly distributed. No biochemical test was able to distinguish between bacteraemic and faecal control strains. Strains from patients with diabetes mellitus were grouped in 11 clusters containing 2-14 strains and 22 'outliers'. The low diversity index of bacteraemic strains obtained from diabetic patients as compared to other strains indicated a greater homogenicity. However, no correlation was observed between the examined host factors and the clusters.