more on tomatoes

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Posting from another web site. Very scary!

Sharon Salomon, MS, RD

Bugs can enter and grow in fresh veggies: washing is not enough

Posted on May 28, 2008 by Doug

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Researchers in Austria and France report today that Salmonella can

infect plant cells and successfully evade all the defence mechanisms of

plants, meaning that cleaning the surfaces of raw fruits and vegetables

is not sufficient to protect against food poisoning.

Work carried out by a team led by geneticist Prof. Heribert Hirt, and

published today in PloS ONE, shows that the strain of bacteria known as

Salmonella typhimurium can also invade, and multiply inside, plant

cells. It is already known that Salmonella can survive for up to 900

days in contaminated soils, which creates a rich source of infection for

plant material. However, Prof. Hirt's team can now show that bacteria

from such a source can actively achieve the infection of plant cells,

thereby disproving the previous assumption that infection was

coincidental and - as regards the bacteria - passive.

" We marked individual bacteria with a fluorescent protein, which enabled

us to observe them as they quite clearly penetrated root cells and

multiplied. Just three hours after the bacteria came into contact with

the roots, they had penetrated inside the cells of the finest root

hairs. 17 hours later, the cells inside of the roots had also become

infected. …

" The defence mechanisms fail completely. Although regulating proteins

such as the two mitogen-activated protein kinases 3 and 6 are activated

just 15 minutes after Salmonella has infected the plant, they cannot

prevent the bacteria from multiplying. Another defence mechanism, which

is activated by the plant messengers salicylic acid, jasmonic acid and

ethylene, proves similarly ineffective. Although these messengers are

important to coregraph the plant defense responses, they too are unable

to halt the infection. "

Previous work has shown that pathogens can enter the inside of tomatoes,

leafy greens and cantaloupe. The current work once again demonstrates

that food safety begins on the farm, and that food safety messages to

cook, clean, chill and separate are seriously deficient. To quote again

from the press release,

" If, as has now been discovered, Salmonella survives and multiplies in

plant cells, then washing raw fruit and vegetables does nothing to

prevent food poisoning. "

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