This month Tom Besser, professor of veterinary microbiology at Washington State University, received $1 million from the Federal Agriculture and Food Research Initiative. This money will be used to evaluate whether previous research done on stopping E. coli O157:H7 in cattle may be more effective once different strains of the disease are considered.
The three-year U.S. Department of Agriculture grant will fund work in finding genetic markers that clearly define differences in five strains of E. coli.
Besser said the next step is to, “sequence strains of bovine-biased genotypes to identify single nucleotide polymorphisms (SNPs) to use to identify lineages, and show that these SNPs are an accurate and consistent typing method.”
The grant will also involve an outreach program targeted at improving the accuracy of E. coli O157:H7 information going to industry, the media, health professionals, and policy makers.
An average of 70,000 Americans per year are infected with E coli O157:H7; yet researches have not been able to prevent the spread of the bacterium. Although health experts have worked on reducing the infection rate through meat handling and food preparation, it takes only ten E coli cells to infect a person with the illness.
“Cattle don’t get sick from this,” Besser said. “It doesn’t bother them. But that still doesn’t mean we can’t go into cattle and maybe do something to reduce their infection rate with O157. And we think if we do, then depending on how important cattle are as a source for humans, the human rate should go down, too.”
Besser’s goal is to stop the bacteria by focusing on beef and dairy cattle and the numerous types of E. coli they hold.
Researchers have been shocked by how the bacterium seems to die off in the winter months and come back strong in the summer months. Besser has seen promising work in the reduction of the number of infected cattle, and thinks researchers might see even more striking results if they take different E coli strains into account.
Two strains, called clinical genotypes, tend to be the most infectious, being found in 95 percent of human illnesses. Another group of three strains, the “bovine-based” genotypes, is found in only five percent of human illnesses.
Being that strain types had not yet been discovered when most of this research was done, researchers were not able to determine which strains were involved when testing the effectiveness of different vaccines, feeds, and treatments.
“We’ve got 15 or 20 years of research on O157:H7 in cattle and we don’t have a clue in any of those research projects whether we were measuring bovine-biased genotypes or clinical genotypes,” said Besser. “And those interventions that we studied–the vaccines and the probiotics and the seasonal variation and everything else–it would be really helpful to know whether the bovine-biased genotypes behaved differently than the clinical genotypes for those things.”
A vaccine could be a very good thing, especially if it is cutting the illnesses caused by the clinical genotypes in half. Besser says, “At least two vaccines have been developed. For one of them (provisionally licensed in Canada, license pending in the U.S.), there is quite a bit of data showing it has a beneficial effect although it is not effective enough to eliminate E. coli. The other vaccine is provisionally licensed in the U.S. but only one study has been published so far and it failed to show a beneficial effect. I’m very skeptical that any vaccine will ever be effective enough to eliminate E. coli O157:H7.”
“We’ve spent a lot of money over the years trying to investigate feeds and management systems and manure handling systems,” he said. “Now that we know about these genotype differences, I want to go back and say, ‘Well, maybe some of those interventions that looked effective really aren’t very effective and we should write them off. Or maybe some of them that didn’t look very effective actually were much more effective than we thought.’ And I don’t think this is a far-fetched possibility. I think it’s quite possible.”