One dairy cow in Kentucky is an example of how antibacterial drugs could be getting into the food supply.

Sulfamethazine is a sulfa drug used to treat bacterial diseases in humans and animals, and to promote growth in cattle, sheep, pigs, and poultry.

The U.S. Food and Drug Administration (FDA) has established a tolerance of no more than 0.1 parts per million (PPM) for residues of sulfamethazine in the uncooked edible tissues of cattle.

Last July 6, Kelly Poynter, Sr., a Cave City, KY farmer, sold a culled dairy cow for slaughter as food.  The next day, the U.S. Department of Agriculture’s Food Safety and Inspection Service collected tissue samples from the animal.

Returned tests of those samples showed the presence of 35.936 ppm of sulfamethazine residue in the liver tissue of the culled dairy cow, or about 323 times higher than the allowed tolerance.

Concern is growing about resistance to commonly prescribed antibiotics in humans, including victims of foodborne illnesses.  Some experts blame overuse and misuse of antibiotics by animal agriculture.

The U.S. Food and Drug Administration (FDA) issued a “Warning Letter” to Poynter on March 15, giving the Kentucky dairy farmer 15 working days to respond in writing with the steps being taken to get back into compliance with the law.

“Our investigation also found that you hold animals under conditions that are so inadequate that medicated animals bearing potentially harmful drug residues are likely to enter the food supply,” Karen Gale Sego, FDA’s Cincinnati District director wrote.

“For example you failed to maintain treatment records.  Food from animals held under such conditions is adulterated within the meaning of section 402(a)(4) of the Act, 21 U.S.C. 342(a)(4).”

FDA also had a problem with how the dairy is using the antibacterial drug.  “We also found that you adulterated the new animal drug sulfamethazine,” Sego added.  “Specifically, our investigation revealed that you did not use sulfamethazine as directed by the approved labeling.  Use of this drug in this manner is extra-label use.”

The extra label use of the drug in lactating dairy cows is illegal, FDA said.  The dosing and withdrawal periods outlined on the label were not followed, causing the drug use to be unsafe.

According to industry literature, the sulfa drug can be given to cattle in either pellets or in granular form.