If you’re regular at Costco or Kroger, avoid buying the chicken next time. Alongside Albertson’s/Safeway, Publix, and Walmart, these massive grocers failed when it came to selling antibiotic-free chicken to the public. All five retailers fell short in a survey conducted by the Natural Resources Defense Council (NRDC), reported OrganicAuthority.com. Each one received a grade of “D” when it came to their lack of progress on the promotion of antibiotic practices, and their inability to provide antibiotic-free chicken offerings.

For their survey, the NRDC looked at the retailers’ branches in Charlotte, Chicago, Houston, Jacksonville, Los Angeles, and Philadelphia. The NRDC selected these cities to represent the country’s four census regions. These locations were then graded according to the following categories: policy (20 points), consumer education at point of purchase (five points), brand score antibiotic use (20 points), and brand score certification (10 points). The raw total of these categories was 55 points, and each grocer scored as such: Walmart received 20.9 points (38 percent), Albertson’s/Safeway received 21.5 points (39 percent), Publix received 21 points (38 percent), Kroger received 18.4 points (33 percent), and Costco received 22 points (40 percent).

Sans Costco, all other retailers scored poorly in policy, which was defined as “Commitment to phase out routine use of antibiotics described on major retailer website” and “Timeline to phase out routine use of antibiotics described on major retailer website.” This was especially notable, as large chicken producers like Tyson and Perdue have moved away from or pledged to move away from the use of antibiotics. Walmart was noted as the biggest offender in this regard. Not only does the company have the most number of suppliers with antibiotic-free chicken products, but Walmart has called for greater transparency from producers. Moreover, the NRDC discovered that the retailers’ own private-label chicken brands were sourced from producers with questionable antibiotic-free practices. (Related: Perdue announces that its chicken products are now 95 percent antibiotic-free)

As for helping consumers in making informed choices, only Publix had the necessary signage in all of their stores. All of their branches had displays that informed consumers of producers with responsible antibiotic policies. However, this did not include producers who were still in the process of phasing out antibiotics from their products. Though all the retailers offered United States Department of Agriculture (USDA)-certified  chicken or Raised Without Antibiotics (RWA) chicken, there were no indications that these poultry products had been certified by third parties.

Whole Foods may not have included in the survey, but the NRDC lauded it as the sole grocer to “have earned top score in all categories.” Their policy to sell antibiotic-free livestock products goes beyond chicken and covers beef, pork, and turkey. Whole Foods also made it easier for consumers to understand their purchases better, something that all the other retailers failed to do.

The NRDC concluded their survey by asking for retailers to commit themselves to the elimination of antibiotic-laden products from their chains, and for consumers to “vote with their wallets” by purchasing RWA and USDA-certified chicken.

Carmen Cordova, a staff scientist under the Food and Agriculture Program of the NRDC, said this about the results of the survey: “The top five grocery store chains in the country feed millions of Americans, so their actions have a big impact on public health — for better or worse. Supermarkets can either continue to ignore the spread of drug-resistant infections, or they can answer their customers’ call to be a part of the solution.”

Rather than curing diseases among chickens, antibiotics are more often used to promote quicker growth in the animals and to prevent them from getting sick. According to OrganicAuthority.com, this practice allows antibiotic-resistant bacteria to thrive, which in turn is extremely harmful to humans and animals alike.