Ripeness of Fruit May Influence Bacteria Growth

LONDONA wide range of fresh produce has been linked to outbreaks of E. coli and Salmonella, and new research presented at the presented at the Society for General Microbiology's spring conference in Dublin suggests the ripeness of fruit may determine how food-poisoning bacteria grow on them. The findings may lead to new strategies and policies to improve food safety.

Researchers at Imperial College London are looking at how bacterial pathogens latch onto fruits and vegetables and establish themselves in the first place. They discovered strains of Salmonella behave differently when attached to ripe and unripe tomatoes.

"Bacteria that attach to ripe tomatoes produce an extensive network of filaments, which is not seen when they attach to the surface of unripe tomatoes. This could affect how they are maintained on the surface," the researchers said. "We are not completely sure yet why this happens; it might be due to the surface properties of the tomatoes or alternatively the expression of ripening hormones."

This is just one example of the subtle interplay between food-poisoning microbes and the fresh produce they contaminate, that determines how pathogens become established in the food chain. "Apart from Salmonella, strains of E. coli are also particularly devious in the way they interact with plant surfaces. They have hair-like appendages and flagella they can use as hooks to successfully secure themselves onto things like salad leaves," they added.

The researchers noted by working out the reasons behind sporadic outbreaks of infections, they can control them better and help maintain consumer confidence.