Unfortunately not only flowers and veggies grow in soil, but very unpleasant and mostly resistant bacteria called Burkholderia cepacia which puts the health of CF patients seriously at risk.
B. cepacia are typically found in water and soil and can survive for prolonged periods in moist environments. Previously known as the cause of one certain type of foul on onion-like plants, garlic, onion, etc., the species is often to be found in the area of the plant roots, attacks young onions and displays a remarkable ability to digest oil.(1)
If your child or you have CF, consider avoiding gardening. If not, do your plant work with a mask and gloves, desinfect your hands thereafter! Be aware of possible cross infections. (2)
Do not consume onions with signs of foul. Eat veggies and fruits without signs of foul as much as you like.(2)
(2) Medical University Children’s Clinic CF-Center at the AKH-Vienna