Studies on Escherichia coli vaccines: estimation of endotoxins in veterinary vaccines.

Fifteen batches of E. coli vaccines for pigs, from three different manufacturers, were subjected to a quantitative form of the in vitro Limulus-amoebocyte-lysate (LAL) test for their free endotoxin content. A batch of vaccine associated with abortions in pregnant sows was found to contain a much higher level of free endotoxin than batches of vaccine not associated with abortion. The evidence of these assays suggests that they will be useful in the quality control of E. coli vaccines.