Stability of thermolabile (LT) enterotoxin produced from enterotoxigenic Escherichia coli strains maintained in vitro

The stability of thermolabile (LT) enterotoxin in 26 strains of porcine enterotoxigenic Escherichia coli (PETEC) belonging to serogroups 08 and 0149 was assayed by the passive immune hemolysis (PIH) test, over a period of 9 months at -70 degrees C. It was found that the percentage of LT+ colonies (% LT+) and the mean value of hemoglobin release (XHb), could predict a change from LT+ to LT-.