The effect of iron compounds on the virulence of Escherichia coli for guinea-pigs.

Ferric ammonium citrate, haematin hydrochloride, lysed guinea-pig red cells and crystalline human haemoglobin greatly enhanced the virulence of Escherichia coli 0111/B4/H2 when injected intraperitoneally into normal guinea-pigs. The viable counts of E. coli in the peritoneal fluid of normal guinea-pigs given a sub-lethal infection were very variable and the bacteria eventually disappeared. In lethal infections in animals treated with iron compounds the bacteria grew extremely rapidly and death occurred when the counts reached 109–1010/ml of peritoneal fluid. It is suggested that the mechanisms underlying non-specific immunity of guinea-pigs to E. coli may not be dissimilar to those involved in passive immunity to Clostridium welchii Type A in guinea-pigs, and in passive immunity to Pasteurella septica in mice.