If you don’t eat meat or work on a farm, are the dangerous resistant bacteria that develop in livestock a threat to your health?
It’s a timely question, as a wave of virulent multi-drug-resistant bacteria find their way onto our plates due in part to the reckless overuse of antibiotics on factory farms. According to the Centers for Disease Control and Prevention (CDC) “each year, antibiotic-resistant infections from foodborne germs cause an estimated 430,000 illnesses in the United States.”
Unfortunately for the meat-avoiders among us, the answer is pretty clear: Even if you are a vegetarian and have never been on a farm, these resistant bacteria can make you sick.
There are two primary ways this can happen.
First, resistant bacteria from animals treated with antibiotics end up on vegetables and other non-meat foods via manure used for fertilizer, on the hands of farmworkers, from the waste of animals that defecate in fields, or through contaminated cooking surfaces in homes and restaurants. One study by the Center for Science in the Public Interest (CSPI) looked at 38 resistant outbreaks between 1973 and 2011: two of the outbreaks were transmitted via produce, 12 involved dairy, and four were from unknown sources. [pdf] 
Second, consumers who avoid meat can be exposed to resistant bacteria through their environment, by bacteria carried in the wind from factory farms. A study at the Veterans Affairs hospital in Iowa City found that patients who lived within one mile of a large factory farm were nearly three times as likely to carry the drug-resistant MRSA bacteria as other patients.
Based on everything scientists know about food-borne infections, there’s plenty of reason to believe that you can contract a superbug from an animal via a vegetable. General data on food-borne illness, whether resistant to drugs or not, make clear that animal bacteria contaminate vegetables and other non-animal products all the time. As recently as August 2014, an E. coli outbreak that sickened 19 people was linked to raw clover sprouts. The CDC’s selected list of multi-state outbreaks is filled with bacterial infection outbreaks caused by non-animal foods. And in the CDC’s Foodborne Outbreak Online Database (FOOD), which provides some public data on outbreaks in the United States, more than one third of the illnesses caused by Campylobacter, Salmonella and E. coli came from non-animal sources (1,035 non-meat illnesses out of 3,096 total).  We’re lucky that not all of the bugs that caused these infections have developed antibiotic resistance.
The overuse of antibiotics on factory farms threatens not just meat eaters and farm workers. Once more, the CDC: “Up to half of antibiotic use in humans and much of antibiotic use in animals is unnecessary and inappropriate and makes everyone less safe.” The resistant bacteria that develop on factory farms can – and do – find their way into non-animal foods and the environment, putting the “public” in “public health threat.”
 There is not great tracking of antibiotic resistant outbreaks, so this data is far from comprehensive. CSPI notes that the current systems for tracking antibiotic resistance are lacking, and don’t associate resistance with specific food outbreaks.
 These numbers were calculated from data downloaded from the CDC’s Foodborne Outbreak Online Database. I looked at illnesses from 2012 caused by Salmonella, Campylobacter, and E. Coli, and only counted outbreak incidents where it was clear that animal products (including eggs and dairy) were not the source.