Lectin Ingestion: Changes in Mucin Secretion and Bacterial Adhesion to Intestinal Tissue

Phytohemagglutinin (PHA), the lectin derived from red kidney been (
Phaseolus vulgarus
) causes reduced growth rates in several animal species, when incorporated at 0.5–5% of dietary protein. Lectin feeding results in diarrhea, impaired nutrient absorption, growth rate inhibition, and can even lead to the eventual death of PHA-fed animals. These effects are believed to result from changes in the autochthonous microflora induced by the presence of PHA in the diet, as germ-free animals do not display the same changes seen in conventional animals (
1
-
11
) Jayne-Williams’ (
1
,
2
) now classical studies in the quail clearly demonstrate this point. It is established that these adverse effects are the result of PHA-induced changes in the normal endogenous flora and are not due to lectin selection of specific pathogenic bacteria (
9
,
10
) The major change appears in the levels of facultative aerobes, which increase in PHA-fed animals without an increase in obligate anaerobes (
2
,
6
). These observations separate the effects of PHA feeding from blind loop syndrome or other stressrelated changes in bacterial flora, in which anaerobic bacterial overgrowth is observed (
12
,
13
). Phytohemagglutinin feeding has also been observed to affect small intestinal growth (
14
).