Aerobactin production and plasmid distribution in Escherichia coli clinical isolates.

The distribution of plasmids as a function of aerobactin production, antibiotic resistance and antimicrobial agents production was studied in 139 Escherichia coli strains obtained from clinical sources. Ninety eight per cent of the strains analyzed presented plasmids with a median value of 2.97 plasmids per cell. Differences in the number of plasmids were observed for aerobactin production (3.52 for aerobactin producing strains, 2.56 (for non-producing ones) and antibiotic resistance (3.19 for antibiotic resistant strains and 2.58 for the sensitive ones). But this was not the case for antibacterial agent production (2.96 for the producing strains, 2.98 for the non-producing ones. Ecological implications of these results are discussed.