Purification of the polymyxin-released, heat-labile enterotoxin of Escherichia coli.

The heat-labile enterotoxin of Escherichia coli strain H-10407 has been purified by use of a commercially available affinity gel (Affi-Gel 202). This gel possesses a strong and highly specific affinity for the enterotoxin released from intact E. coli cells by polymyxin B. The polymyxin-release technique could be used with fermenter-size batches of E. coli cells grown in a casamino acids-yeast extract medium. With a simple (NH4)2SO4 back-extraction step prior to affinity chromatography, large batches of E. coli enterotoxin could be processed rapidly. Affi-Gel 202-purified E. coli enterotoxin produced a single precipitin band in the presence of several different antisera against crude preparations of the toxin. The same antigen produced a precipitin band in the presence of both cholera antitoxin and antiserum to choleragenoid.