Bacterial synergism between the enterococcus and Escherichia coli.

The pathogenicity of the enterococcus in surgical infections remains unclear. To examine this issue, rats received an intravascular infusion of 10(9) enterococcus. No rats died. Rats that received a sublethal inoculum of Escherichia coli with 5 X 10(8) enterococcus had a 40% mortality (P less than 0.05). Cutaneous infections in rabbits with E. coli, Bacteroides fragilis, and enterococcus were examined singly and in combination. Infections with E. coli measured 21 +/- 1 mm, with enterococcus were 15 +/- 1 mm, and with B. fragilis were 9 +/- 1 mm in diameter. When E. coli and enterococcus were combined together, significantly larger cutaneous infections were noted (P less than 0.05). No apparent synergism existed between the enterococcus and B. fragilis. These data indicate a synergistic relationship between the enterococcus and E. coli.