I keep my turtles in a pin next to my vegetable garden and haven't worried about the possibility of getting sick until the recent jalapeno scare.
You say, “Could?” If they are water turtles – and you have fed them raw meat or chicken that was infected with the bacterium – there is a possibility of cross contamination. If they defecate on the soil in which the vegetables are growing – and their stool is contaminated – the possibility exists. Or if there is run-off from the water they swim in – and the water is contaminated – the possibility exists. Or if you use their swimming water (literally their toilet) to water your plants – the possibility exists – IF THERE IS CONTAMINATION from Mr. and Mrs. Sal Monella. If you keep them in a “pen” and they are land turtles you are feeding fruits, vegetables and whatever insects/worms they can find – the chances are highly UNLIKELY and I wouldn’t worry.
