Despite federal authorities’ attempts to curb the widespread use of antibiotics in the food industry, bacteria that cause foodborne illnesses are continuing to develop more resistance to antibiotics, the Centers for Disease Prevention and Control (CDC) found in a recent study.
To prevent disease and promote growth in animals, the meat industry broadly adds antibiotics into animal feed or injects the drugs directly into livestock. But as the drugs get overused, they lose their effectiveness at inhibiting or killing bacteria. Foodborne bacteria can thus make their way through the food supply chain to the supermarket, where consumers could potentially buy contaminated food.
The CDC estimates that antibiotic-resistant infections from foodborne germs cause about 440,000 illnesses in the country each year.
The federal government is starting to tackle antibiotic resistance by collecting more accurate data on how much antibiotics the food industry uses, and also meeting with food industry representatives to discuss reducing the amount of antibiotics used to raise animals.
But those efforts haven’t halted the advance of the phenomenon.
In a report released Tuesday, June 10, the CDC found that some common bacteria have actually increased their resistance in the past few years: a common variation of salmonella grew resistance to four different antibiotic drugs, rising from 18 percent resistant in 2011 to 46 percent resistant in 2013.
In a strain known as nontyphoidal salmonella, resistance grew from an average of 15.7 percent between 2004 and 2008, to 19.2 percent in 2013. The CDC said infections from this bacterial strain are often underdiagnosed, and estimates that more than 1 million cases of infections occur annually.
Salmonella is a common bacteria in animals’ intestinal tracts. Humans can get infected through contaminated egg, meat, poultry, or milk products. Vegetable-based products contaminated by animal manure can also contain the bacteria. Food processing company ConAgra Foods was recently fined $11.2 million for a salmonella outbreak in 2006 linked to its peanut butter.
The CDC also found that one in four samples of campylobacter bacteria from infected individuals are resistant to a class of antibacterial drugs called quinolones.
Campylobacter is the leading cause of bacterial diarrhea, and causes 1.3 million infections a year, according to the CDC.
The bacteria is commonly found in raw chicken and raw milk, but can usually be killed by properly cooking the chicken or pasteurizing the milk.
Antibiotic resistance also grew significantly in shigella (2 percent between 2004 and 2008 to 5.2 percent in 2013), a human pathogen that causes about 300,000 infections a year.
The bacteria has been found in salads, raw vegetables, dairy products, and poultry. They were likely contaminated through food handlers who did not wash their hands properly, or through water contaminated by human feces.
As consumers become more aware of antibiotic resistance, some meat producers have promised to completely stop using antibiotics, while restaurants like McDonald’s announced that they will no longer buy chickens raised on antibiotics to make their food.