Endotoxin Studies in Chicks

The chicken is used infrequently as a test species for endotoxin studies. Jordan and Hinshaw (7) reported that chickens survived intravenous inoculations of endotoxin of up to 40 mg/kg, and Cole and Boyd (2) found no visible reaction to 2 mg of endotoxin in two-week-old chicks. Berczi et al. (1), working with chickens weighing 1?0.2 kg, found the lethal dose (mg/kg) to be in excess of 50 mg. The endotoxins used by all the above workers had been obtained from strains of Escherichia coli. During a study on pathogenic mechanisms in avian strains of E. coli it was found that two-week-old chicks were susceptible to endotoxins prepared by NaCl extraction from certain strains of E. coli (11). Such extracts possessed the ability to cause liver lesions and were also capable of causing mortality. Extracts prepared with trichloroacetic acid or phenol-water and then dialyzed and lyophilized without further purification also caused lesions and mortality. Since, however, the activity of extracts prepared with NaCl were comparable to those obtained by the above techniques, NaCl was used in the following study to ascertain the relative activity of extracts prepared from different serogroups of E. coli and to compare this activity with the virulence of the bacteria from which they were obtained. In addition, other strains and species were used to determine whether these also possessed similar activity.