关键词: 微生物, 发酵床养猪, 生物防治, 大肠杆菌, 毒素基因

Abstract: 【Objective】 The present paper dealt with the distribution of Escherichia coli and it’s virulent genes in the stroma cushion of piggery to explain the biocontrol effects of microbial-fermentation bed on the pig pathogen E. coli.【Method】The bacterium, E. coli isolated from 4 layers in the stroma cushion of piggery in different pig raising periods was analyzed by the method of eosin methylene blue (EMB) medium. The PCR detection was used to conform the species of E. coli by amplifying UdiA gene DNA fragments. The types of virulent genes were detected by the Multiplex–PCR. The simulation models were constructed to analyze the E. coli distribution in the microbial- fermentation bed. 【Result】 The results showed that 419 isolates were detected to be E. coli among 433 samples taken, of which, 59 isolates carried the special virulent genes. A total of 8 types of virulent genes were found, including estB, estA, elt, faeG, fedA, aidA–I, Stx2e and sepA. In the samples,the amount of E. coli had the highest positive rate (22.47%) in the one-month-used microbial-fermentation bed compared to that the lowest positive rate (4.23%) in the nine-month-used microbial-fermentation bed. The population dynamics of E. coli in each layer decreased as the time increased. For the population distribution in different layers, the pathogen E. coli was occupied least in the layer 2, less in the layer 1 or 3, and largest in the layer 4. The virulent genes distribution of E.coli was the similar trend to the population distribution in the piggery. From the dymamic models of E. coli population, it could be seen that the model was y=169.67x-1.0137 in the layer 1, y=0.1006x3-2.3733x2+16.094x-22.454 in the layer 2, y=313.11x-2.1885 in the layer 3, as well as y=0.3159 x3+6.0913x2- 35.634x+ 79.513 in the layer 4, from which, it displayed that the cushion stroma of piggery could inhibit the growth of E. coli by evidence of E. coli in the nine-month-used stroma cushion being much more less than that in the one-month-used stroma cushion with the decreasing rate ranged from 67.45% to 96.53%. It indicated that the microbial-fermentation bed could play an important role in biogicontrol of E.coli in the piggery.【Conclusion】The microbial-fermentation bed could restrain the growth of E.coli, especially for the bacteria carried with the virulent genes. The longer the microbial-fermentation bed was used the stronger the biocontrol effect was on the population of E.coli.

Key words: microbe, microbial-fermentation bed for raring pig, biocontrol, Escherichia coli, virulence gene