A fascinating article in the Cornell Daily Sun about Listeria and Prof. Martin Wiedmann of food science. Dr. Wiedmann has shown that Listeria originate in soil and are transmitted to animals through plant materials. Inside the bodies of mammals, Listeria thrive because there is almost no competition for food. They can invade human cells and even relocate from one cell to the next, avoiding the antibodies the human body produces, Wiedmann explained.
“It has an uncanny ability to survive very, very well. In one case, we found a strain that had survived in a processing plant for 12 years. This may be because it is in the best interest of the bacteria that their hosts are kept alive,” Wiedmann said.
Only two of the existing six strains of Listeria cause disease in humans: L. monocytogenes and L. ivanovii. Wiedmann believes that while all of the strains of Listeria were poisonous in the past, certain strains have become less virulent, or actively poisonous, over time.
Strains continue to evolve, and even among L. monocytogenes, there is a strain that lacks a gene that would make the strain potentially fatal.
Wiedmann studies Listeria’s evolution over a span of 47 million years.