Salmonella doesn't readily infect tomatoes. But when weather combines with a susceptible variety, it creates what University of Florida researchers call a perfect storm for the bacterium to proliferate in harvested tomatoes.

But it remains unclear how much each variable contributes to Salmonella's spread, according to a news release.

The key to curbing produce-associated outbreaks is understanding the process, the researchers said.

Research assistant professor Massimiliano Marvasi led a recently published study that examined three tomato varieties over three seasons and two years.

They were Bonny Best, and heirloom; Florida 47, a widely grown variety; and Solar Fire, a newer variety.

The tomatoes were injected with seven different Salmonella strains.

The researchers found that specific cultivars, combined with drier sunnier conditions, increased the chances of Salmonella spread.

Different Salmonella strains also influenced the infection rate.

And ripe tomatoes were more vulnerable than green tomatoes.

But changing irrigation patterns caused little change in susceptibility.

Although the perfect storm happens rarely, when it does, it can create a public relations nightmare.

Since 2006, 16 Salmonella outbreaks have been linked to tomatoes, cantaloupe, sprouts, cucumbers, mangoes, peanut butter and peppers, in addition to frozen foods containing produce.

The researchers emphasized that less than 1 percent of supermarket produce contains Salmonella or E. coli, and the contamination is only a problem when the food is consumed raw, according to a news release.

Florida tomato growers and packers are required by state law to follow a set of strict food safety measures to further reduce the chances of foodborne illness outbreaks.