Listeria strain discovered which may present new food safety threat

A highly virulent strain of Listeria monocytogenes that may present a new food safety threat has been discovered.

The new strain was identified in a study led by the Institute of Medical Microbiology at the Justus Liebig University Giessen (JLU) as the cause of serious diseases in sheep in a remote area of the Chinese province Jiangsu.

“The detection of a completely new form of pathogenic Listeria monocytogenes in China highlights the need for international collaboration,” said Professor Dr Trinad Chakraborty, Director of the Institute of Medical Microbiology at the JLU and research scientist at the German Center for Infection Research (DZIF). “Only by combining resources and expertise can we rapidly identify newly emerging threats to food safety from highly virulent strains worldwide.”

After decoding the genome sequence of these bacteria, the scientists were able to determine the genetic basis for their hypervirulence. They identified the factors that enhance the ability of this Listeria strain to cause severe septic diseases.

The bacterium Listeria monocytogenes can cause life-threatening infections; contaminated food is a frequent source of infection (credit: S. Doijad, L. La Pietra).

“These isolates are unique in the sense that they combine the virulence characteristics of various highly pathogenic Listeria species that infect animals or humans into a single strain,” continued Professor Chakraborty. “Since listeriosis is a food-borne infection, measures to identify such highly virulent strains are extremely urgent.”

Currently, there are reported listeriosis outbreaks in Germany (Hesse), the Netherlands, Lithuania, Spain, Great Britain, Canada and the United States, posing a particular threat to vulnerable populations. Therefore, considerable efforts are now underway to identify the origin of these pathogens and prevent further outbreaks of listeriosis, the researchers said.