Storage ofEscherichia coli thermolabile enterotoxin on filter papers for assay by immune haemolysis reactions

Thermolabile (LT) enterotoxin was prepared from stationary and shaken cultures of enterotoxigenicEscherichia coli (ETEC) grown in casamino acids-yeast extract medium and dried onto filter discs. These were then examined by a modification of the single radial immune haemolysis (SRIH) test. It was observed that LT antigenicity, as detected by this test, remained unaltered for as long as 30 days at room temperature.