Bringing the European E. coli outbreak under control
A current headline on CNN.com reports that the death toll from the ongoing E. coli outbreak has risen to 35, with over 3200 people having fallen ill to this foodborne illness since it began in early May 2011. Identifying the source of the infection was the job of epidemiologists, who examined common connections between the infected individuals. Despite some early red herrings, the current culprit appears to be vegetable sprouts from Germany, although the method of how those sprouts became contaminated remains unclear.
The infection is transmitted from consuming contaminated food, and after a brief period of incubation leads to moderate to severe gastroenteritis as the pathogenic form of the bacterium begins to cause disease. Many forms of gastroenteritis are treated by basically doing nothing; the infectious agent causes the signs and symptoms of the disease, but eventually it is out-competed by the normal intestinal microorganisms, which causes a decline in the symptoms as the numbers of pathogen decrease.
Of course, one of the major “normal” residents of the intestinal tract is E. coli, and the puzzle arises as to what makes the pathogen in this outbreak such a significant health issue. E. coli is renowned for its ability to cause disease in the human body, and accounts for approximately 25% of the hospital acquired (nosocomial) infections with a huge increase in the costs of patient care. A recent report on Science Daily describes the very current work being done with the isolates obtained from the Germany outbreak.
Researchers at the Virginia Bioinformatics Institute at Virginia Tech have sequenced the genomes of two isolates of E. coli O104:H4. The isolates are similar to the more commonly known E. coli O157 strains that are mentioned as causative agents of foodborne illness. These pathogenic strains differ from the more innocuous strains in our intestinal tract by possessing genes encoding potent toxins. The new strain carries the genetic information for a protein called Shiga toxin, which is able to block protein synthesis in eukaryotic cells by damaging the ribosome. The toxin is particularly damaging to renal cells. As a result, a common complication due to infection with this E. coli strain is kidney damage if the bacterium is able to escape the intestinal tract and infect the bloodstream. Treatment for these complications is difficult, as the damage done by the toxin in the cell is irreversible, and it is necessary for new cellular growth to replace the damaged cells.
Sequencing of these isolates gives insight into the mechanism by which these strains are able to cause disease, but more importantly can give an indication as to the origin of these strains. This in turn can allow epidemiologists to track how the outbreak originated and hopefully enable them to prevent future outbreaks.
Posted on June 13, 2011, in Microbes in the News, You are what you eat and tagged Escherichia coli, Foodborne illness, World Health Organization. Bookmark the permalink. Comments Off on Bringing the European E. coli outbreak under control.