BALTIMORE — A federal judge issued a preliminary injunction Tuesday barring Tyson Foods from advertising that its poultry products don't contain antibiotics thought to lead to drug resistance in humans.

The ruling by U.S. District Judge Richard Bennett was a victory for rivals Perdue Farms and Sanderson Farms Inc., who are suing to stop the advertisements.

Salisbury-based Perdue and Sanderson, based in Laurel, Miss., argued the advertisements are misleading because none of the companies uses those types of drugs, and shoppers could be led to think other companies are using the drugs.

Bennett said he was convinced "that the consumer public is being misled" by the "Raised Without Antibiotics" advertising.

All three companies use feed containing ionophores, which are largely considered to be antibiotics. However, the substances are not used in humans and thus are not believed to raise human health concerns.

Last spring, the U.S. Department of Agriculture said Tyson, based in Springdale, Ark., could label its foods as "raised without antibiotics," but the USDA later reversed that decision after Tyson had spent money on advertising and packaging.