How Can Tomatoes Get Salmonella?

Salmonella is a bacteria that causes the most food-borne illnesses, mostly diarrhea, in humans. Salmonella is a rod-shaped microscopic living thing that is easily transferred through food and animals to humans. There are more than 2,300 types of salmonella and they do not affect the smell, taste, or appearance of the food they infect. Though it is difficult to imagine how salmonella could manage to get inside tomatoes, there are a number of ways through which this can happen.

Manure

• When large numbers of livestock animals are kept in confined places, they can contract the bacteria without exhibiting any outward symptoms. The bacteria is then released through their waste and this waste is often used to fertilize produce fields, leading the bacteria to the tomatoes. Though the heat used during the composting of manure does kill the majority of bacteria, many still manage to survive and can get transferred to produce, such as tomatoes.

Contaminated Water

• Water supplies that are contaminated are another cause of salmonella in tomatoes. Leaky waste lagoons and runoff water from livestock pastures can contaminate ground water, streams, or other water sources used by farmers for irrigation, leading to salmonella in tomatoes. For instance, a Food and Drug Administration (FDA) investigation revealed this to be the probable cause of the 2002 outbreak of salmonella in imported stock of Mexican cantaloupes.

Wild Animals

• Wild animals who pass through crops can contaminate the fields either with their own feces or from that which they track in from another place. For instance, the E. coli outbreak in spinach in 2006 was eventually traced back to a pack of wild boars wandering through the spinach fields with contaminated cow manure on their hooves.

Improper Washing

• Though the rule is to wash all produce with chlorinated water to remove bacteria, sometimes enough is left on to cause illness. Also if the skin of a tomato is punctured while being picked or while on sale, it allows the bacteria to get inside. This is the reason why on-the-vine tomatoes were exempted from the last salmonella outbreak scare.

Temperature Difference

• Another way for salmonella to get inside tomatoes is through a temperature difference. Oftentimes tomatoes are picked on very hot days and then placed in cold water to chill. This causes any salmonella on their surface to get sucked up inside the produce.