Researchers at Michigan State University, including microbial evolutionary biologist Thomas Whittam, have phylogenetically analyzed multiple strains of the dangerous E. coli 0157:H7 bacteria (or enterohemorrhagic E. coli, EHEC), and determined that dangerous versions of the bacteria are on the rise. The researchers noticed that outbreaks related to the deadly bacteria can vary in severity. The outbreak in spinach in the United States was much more severe than a similar outbreak in Japan.
This observation spurred the researchers to group different variations of the bacteria into different clades, primarily based on single nucleotide polymorphisms (SNPs). The researchers discovered interesting correlations between different clades.
According to Genome Web:
When they focused in on 39 distinct SNP genotypes and used these to create a phylogenetic network, the team found that the EHEC strains tested fell into nine different clades. Interestingly, there were not only differences in toxin genes between clades, but also in the severity of human infection associated with different clades.
Researchers also noted that the strains in clade eight were associated with severe disease most often found in children or individuals younger than 18. The bacteria in clade eight also had a higher risk of causing hemolytic uremic syndrome (HUS):
Over the past five years or so, Whittam noted, there also seem to be changes in different clades’ prevalence, with clade eight infections apparently increasing and some others decreasing. Still, it’s unclear why clade eight infections are more prevalent — especially in Michigan — in recent years. Whittam speculated that this could be related to the food source that carries the bug, the amount of toxin those strains produce, or some other yet unknown factor.
Whittam and the researchers are hoping that this new breakthrough will help prevent rapid outbreaks associated with E. coli 0157:H7. He would also like to continue the research to developing a quicker way of identifying different strains which could be useful for rapid vegetable-related outbreaks. Whittam also noted that the technique used could help gain greater insight into other forms of E. coli that are not yet known to cause disease in humans.
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