Production of heat-stable enterotoxic component by Escherichia coli strains enteropathogenic for swine.

Forty-nine strains of Escherichia coli isolated from piglets with or without neonatal diarrhea were all negative for both classical heat-labile and heat-stable enterotoxins when examined by the 18-hour rabbit ileal loop test with culture supernatants, the mouse Y1 adrenal cell test, and the infant mouse test. Of them, seven strains from diarrhea were positive only when tested in porcine ileal loops challenged with living bacterial cell suspensions or culture supernatants. The enterotoxic component produced by them was resistant to heating at 80 degrees C for 20 minutes. It presented a rapid onset of action with a long duration, although the amount of accumulated fluid in the porcine ileal loops was small. These porcine strains of E. coli which has been positive only for the porcine ileal loop test were designated "ST pig loop" or "STpl" strains.