Abstract: The objective of this study was to investigate the protective effect of yeast mannatide (MTY) on mice infected with pathogenic Escherichia coli (PEC). Firstly,40 SPF male KM mice were randomly divided into 4 groups:control group, model group, positive drug group and MTY group (10 replicates per group and 1 mouse per replicate). Control group and model group were given normal saline, while the positive drug group and the MTY group were given antibiotic amoxicillin and MTY, respectively. In this paper, the Kunming mice were gavaged MTY for 4 weeks before the challenge experiments with PEC. By analysing enteric microorganism of mice that before challenge test, mortality of mice after PEC infection, organ index, intestinal structure, organs histopathological analysis, and at the same time, observing the physical change of mice in vivo testing, the protective effect of MTY on PEC infected mice was comprehensively evaluated. The results showed that MTY could inhibit PEC proliferation. Compared with blank group, MTY group had significant difference in intestinal microflora (P<0.05), which mainly showed that beneficial bacteria increased and bacterial diversity increased. Compared with model group, MTY treatment can effectively reduce the mortality of mice infection with PEC. MTY significantly increased thymus index (P<0.05), decreased spleen index (P>0.05) and extremely significantly decreased liver index (P<0.01). MTY inhibited the decrease of goblet cells in jejunum of mice (P>0.05). MTY inhibited the down-regulation of MUC2 and ZO-1 expression in intestinal of mice (P<0.05). Therefore, MTY has a good protective effect on intestinal, liver, spleen and lung organs of mice infected with PEC, which has a wide application future in animal feed.In conclusion, oral administration of MTY can reduce the damage of PEC to the body and then play a protective role in mice.

Key words: wall-broken yeast, mannatide, intestinal flora analysis, pathogenic Escherichia coli, histopathological analysis