Ripeness-varying Salmonella behaviour could lead to produce food safety boost

Researchers at Imperial College London have discovered that Salmonella microbes attached to ripe tomatoes produce an extensive network of filaments - behaviour not witnessed when the bacterium to present  on the surface of unripe tomatoes.

Head of the study, professor of molecular pathogenesis Gad Frankel told FoodQualityNews.com that this behaviour could determine how successfully foodborne pathogens such as Salmonella attach and survive on raw produce such as tomatoes.

Frankel added that understanding how Salmonella behaves on the surface of ripe and unripe tomatoes could lead to new strategies to improve food safety.

Prevent Salmonella survival​

“The fact that Salmonella bacterium is responding differently at different stages of ripeness is very interesting,”​ said Frankel.

“We are interested to know how Salmonella microbes firstly attach to tomatoes and how they manage to survive. Through this research, we are looking to establish whether we can prevent the attachment and survival of Salmonella on tomatoes.”​

“We want to make sure we are using the most effective composition for washing tomatoes,”​ he said.

According to Frankel, when attached to green un-ripened tomatoes, Salmonella microbes appear smooth under a microscope. However, when present on red ripened samples the bacterium appeared to produce filament.

“It appears that Salmonella microbes have a sense of whether or not they are attached to red or green tomatoes."​

“We need to check whether filaments make a difference and if they have a stronger attachment – it is one possibility, but it’s not proven yet,”​ Frankel added.

However, he added that translating this research into new decontamination practices is a challenge for future studies.

Tainted tomatoes​

In recent years, tomatoes and similar products such as jalapeno and Serrano peppers have been implicated in several foodborne disease outbreaks.

In December 2011, US and Canadian food safety authorities issued separate warnings on a brand of jalapeno and Serrano peppers that were potentially contaminated with Salmonella.

The peppers became the subject of a recall in the US and a product warning in Canada after a random US Department of Agriculture (USDA) sample of the product was found to be contamination with potentially deadly Salmonella.

Tomatoes were falsely implicated in an outbreak of Salmonella in the US in 2008. The contamination, which went on to infect around 1,500 people and kill two people in the country, was later attributed to tainted Mexican peppers.