The bacteriostatic effect of serum on Pasteurella septica and its abolition by iron compounds.

Methods are described for controlling the oxygen tension and pH of bacterial cultures in vitro. In fresh normal rabbit serum or plasma at a Po2 of 80–90 mmHg and a pH of 7.5, the presence of specific antibody has a powerful bacteriostatic effect against Pasteurella septica. It is suggested that the serum components involved in this reaction consist of transferrin, specific antibody, and complement. Bacteriostasis can be abolished by a variety of iron compounds. This evidence together with that obtained in vivo (Bullen, Wilson, Cushnie and Rogers, 1968a) strongly suggests that an interference with bacterial iron metabolism plays an important role in resistance to infection against P. septica.