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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Research » Publications at this Location » Publication #107884
Title: THE GENETIC DIVERSITY OF PREDOMINANT ESCHERICHIA COLI STRAINS ISOLATED FROMCATTLE FED VARIOUS AMOUNTS OF HAY AND GRAIN

Author
item JARVIS, GRAEME - CORNELL UNIVERSITY
item KIZOULIS, MENAS - CORNELL UNIVERSITY
item DIEZ, FRANCISCO - CORNELL UNIVERSITY
item Russell, James

Submitted to: Microbial Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: E. coli is found in the GI tract of all animals, but some strains (e.g. O157:H7) are pathogenic in humans. Large numbers of cattle carry E. coli O157:H7, but the ecology of E. coli populations in cattle was not understood. We isolated predominant strains of E. coli from cattle fed different proportions of hay and grain and used a variety of molecular techniques to characterize them. Results indicated that the diversity of E. coli was very great, and the animal itself had a large impact on the type of E. coli that was found in the colon.

Technical Abstract: When cattle were fed increasing amounts of grain (0 to 90%), the volatile fatty acid concentration of the rumen and colon increased, but the effect on colonic fermentation was greater. Ruminal pH was never less than 6.1, but colonic pH values were as low as 5.4. Grain feeding promoted the growth of colonic E. coli. Predominant E. coli strains (n = 44) were isolated from the rumen and colon on each diet on 4 consecutive days. The 16S rDNA of each strain was amplified by PCR and digested Hha III and Hae I, and unweighted pair group analyses of the fragments indicated that the stains could subdivided into 4 ribo-patterns. Most of the isolates from both cows were from ribo-pattern B, and only cow 1 had all 4 ribo-patterns. When the chromosomal DNA was digested with Xba I and subjected to pulse gel electrophoresis, the strains fell into 24 genotypes (< 95% similarity) and 4 clads (> 40% similarity). Genotype varied with sampling day, but clads were typically the same on 3 or 4 days. All 4 clads were isolated from th rumen and colon. However, cow 1 never had clad III and cow 2 never had clad II. Animal effects masked diet effects, but when the amount of grain was increased, number of clad II in cow 1 increased. Only 8 of the 44 strains carried shiga toxin genes, and none of carried the intimin gene. None of the strains had both O157 and H7 antigens. When all 22 colonic E. coli strains were inoculated into a maltose-limited chemostat, only a single genotype persisted. Based on these results, the genetic diversity of E. coli in the GI tract is very great, and E. coli can occupy different niches .