Guinea-pig ileal loop assay: a better replacement of the suckling mouse assay for detection of heat-stable enterotoxins of Escherichia coli.
The suitability of guinea-pig ileal loop assay (GILA) for the assay of heat-stable (ST) enterotoxin was confirmed. Secretory response against Escherichia coli heat-stable enterotoxin in this model was determined in terms of dilatation index (DI). DI equal to 0.50 or more was considered as a positive secretory response. Kinetics of fluid accumulation and the titration of toxin in guinea-pig ileal loop suggest uniform secretory response throughout the small intestine and 31.5 microgram of crude ST toxin as the minimum effective dose to induce a DI of 0.5. Guinea-pig intestine was found sensitive to both methanol soluble (STa) and methanol insoluble (STb) toxins of E. coli and so was considered superior to the existing suckling mouse assay (SMA), which is known to be sensitive only to STa toxin. In addition, GILA was also found to be more suitable and economical as at least 10 strains together with the positive and negative controls can be tested in one animal, whereas in SMA, four suckling mice were needed to test a single strain. Hence, in SMA individual susceptibility among mice cannot be ruled out. GILA was considered to be an alternative to the presently available test, SMA, in the determination of ST toxin of E. coli.
Choudhry
M A
MA
Division of Microbiology, Central Drug Research Institute, Lucknow, India.
Gupta
S
S
Yadava
J N
JN
D000818:Animals; D000833:Animals, Suckling / Q000382:microbiology; D001427:Bacterial Toxins / Q000032:analysis*; D001681:Biological Assay / Q000379:methods; D004768:Enterotoxins / Q000032:analysis*; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D006168:Guinea Pigs; D007082:Ileum / Q000382:microbiology; D051379:Mice; D012680:Sensitivity and Specificity
D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; C034151:heat stable toxin (E coli); C027538:heat-labile enterotoxin, E coli