Archives

"Bacteria eaters" demonstrate potential to reduce E. coli in cattle

An old option for treating bacterial infections could provide a major new tool in the battle for food safety, says a researcher presenting study findings at the National Beef Science Seminar in Calgary.

Researchers believe that using cost-effective bacteriophage therapy to control infection of cattle with bacteria such as E. coli O157:H7, could reduce the transfer of dangerous pathogens to humans, says Dr. Roger Johnson, a Health Canada researcher now with the new Public Health Agency of Canada. Bacteriophage therapy was a method originally studied before the arrival of antibiotics that is now receiving new attention.

Bacteriophages, literally bacteria eaters, are bacterium-specific viruses found in sewage, water and fecal material, explains Johnson. Bacteriophages, also called phages, invade a bacterium and once inside, grow, multiply and eventually burst out of the bacterium, killing it in the process.

Johnson and colleagues recently completed a study, funded by the Canada Alberta Beef Industry Development Fund (CABIDF), to find effective phage therapy strategies for reducing or eliminating the carriage of E. coli O157:H7 and Salmonella Typhimurium DT104 by cattle. Eliminating the occurrence of these bacteria in cattle would be a significant step in keeping Canada's beef industry competitive in the marketplace and it might help deal with concerns about the rise of antimicrobial resistance, says Johnson.

While E. coli O157:H7 does not cause health problems in cattle, this bacterium can have a serious impact on human health - as was seen in the Walkerton, Ont., outbreak. S. Typhimurium DT104 causes significant health problems in cattle and humans.

"Our evaluation of phages in experimentally infected calves provided a proof of concept that phage therapy has potential to combat E. coli O157:H7 in healthy cattle and other ruminants," says Johnson. "However, we did not have the same success with the phages we selected for S. Typhimurium DT104."

With respect to E. coli O157:H7, apart from antibiotic treatment, no other current interventions, including dietary factors, probiotics and vaccination, have proven effective in eliminating the organism from cattle, he says. And antibiotic therapy is increasingly of concern in human and animal health because of the emergence of antibiotic resistant bacteria.

"Phage therapy was actually studied quite extensively prior to the introduction of antibiotics," says Johnson. "Today, there are many practical new reasons to study phage therapy, and there are benefits to beef producers and the industry as a whole. Phages are economical to produce, hardy and self-replicating. They potentially can be prepared economically in a dried form with a protective coating against stomach acids that enables them to be used in feed."

If used at calving, weaning, and induction into feedlots, phage therapy could greatly reduce dissemination of E. coli O157:H7 in cattle and the environment, he says. Treatment prior to slaughter would reduce the bacterial load in feces and on hides, and hence reduce the risk of carcass contamination during slaughter.

In the study, researchers evaluated candidate phages for the attributes considered important for phage therapy, then tested these phages in experimentally infected calves, under biocontainment. "In our project, phage therapy eliminated E. coli O157:H7 from experimentally infected calves, without adverse effects," says Johnson. "The treated calves stopped shedding E. coli O157:H7 significantly sooner than untreated calves."

Results for S. Typhimurium DT104 were less encouraging. Treated calves shed fewer S. Typhimurium DT104 for shorter periods than did untreated calves, but the differences were not significant.

This year's National Beef Science Seminar was designed to showcase results of the Canada Alberta Beef Industry Development Fund (CABIDF). More information on the phage therapy study and the nearly 60 other CABIDF-funded beef research projects is available on the CABIDF Web site, www.albertabeef.org/CABIDF.

Alberta producers can also request one of a limited number of CDs that contain full information on each project, including the actual technical reports researchers delivered to CABIDF upon completion of their projects, by contacting the Alberta Beef Producers office at (403) 275-4400.

For more information, read the research report on the CABIDF Web site.

© 2004 Meristem Information Resources Ltd.
Meristem® is a registered trademark of Meristem Information Resources Ltd. All rights reserved.
Legal Disclaimer