Though the levels may be at trace, antibiotics have been found in distillers’ grains (DGs), which are used to feed animals. Though this wouldn’t seem a problem at first, the continued consumption of DGs by animals may cause some bacterial resistance to antibiotics, depending on the bacterium and the antibiotic in question, according to findings in a report from the Institute for Agriculture and Trade Policy (IATP).

Corn ethanol
The making of corn ethanol often uses antibiotics to increase yield.

The report, Bugs in the System: How the FDA Fails to Regulate Antibiotics in Ethanol Production, suggests FDA has taken a lax stance on the use of antibiotics in livestock or poultry feed, refusing to place binding regulations on producers that would limit their antibiotic use. IATP suggests FDA take another look at the use of antibiotics in the corn ethanol industry.

Three years ago, food safety and public health advocates began to recognize that another sector of agriculture—the corn ethanol industry—also played a role in antibiotic misuse. Many ethanol producers routinely add antibiotics such as penicillin and erythromycin (both important for human health) and virginiamycin and tylosin (both have analogs used to treat humans) to the tanks where they mix corn mash with warm water to ferment ethanol, according to IATP. Bacteria outbreaks are common in ethanol plants and can lead to yield losses.

Regarding antibiotics added directly to livestock feed, FDA has not restricted the marketing or use of antibiotics in ethanol production, nor has the agency prohibited or limited sales of DGs that are contaminated with antibiotic residues. The FDA has ruled, however, that antibiotics used in ethanol production should be treated as food additives, and thus require FDA approval before they can be used, according to IATP.

The report is concerned with what trace levels of antibiotics may be high enough to encourage resistance of bacteria. For example, in a CVM study, researchers found that virginiamycin and penicillin at the levels present in DGs samples “did not select for resistance” (i.e., allow the susceptible bacteria to die off and the resistant bacteria to thrive) among Campylobacter bacteria or Enterococcus bacteria. Erythromycin, however, at the 0.58 ppm level found in DGs samples, did select for resistance in Enterococcus bacteria.

IATP, therefore, suggests residues of antibiotics in DGs have the potential to cause increased antibiotic resistance, which can have an impact on the human population. To read the report in full, download it from the IATP website.