A truck enters the Foster Farms processing plant, Oct. 10, 2013, in Livingston, Calif. (Credit: Rich Pedroncelli/AP Photo)

Federal officials decided not to close the California poultry farm packaging plants at the center of a salmonella outbreak that has sickened nearly 300 people in 18 states.

The United States Department of Agriculture sent a letter to Foster Farms in Fresno, Calif., on Oct. 7, explaining that 25.33 percent of the farm's poultry tested positive for salmonella, and many of those salmonella strains matched the recent outbreak. Foster Farms responded to the letter on Thursday with plans to improve food safety, which the USDA deemed sufficient to keep the farm open.

But ABC News' chief health and medical editor Dr. Richard Besser said he would avoid Foster Farms' chicken anyway because this particular strain of salmonella has sent more people to the hospital than usual, and it's proven to be resistant to antibiotics.

"I have to tell you that the outbreak is still going on," Besser said today on Good Morning America. "There were three new cases yesterday. Until this is over, I would still stay away from this chicken."

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He also noted that the departments handling the outbreak are understaffed because of the government shutdown.

"How do we know this is truly over if our public health system isn't there?" Besser said.

USDA inspectors wrote in their Oct. 7 letter that Foster Farms' food safety system was inadequate and said if the farm didn't respond to the USDA with a plan to address the problems within three business days, the USDA would either refuse to inspect its products or mark them as "adulterated."

According to the Oct. 7 letter, food safety inspectors found that Foster Farms had "poor sanitary dressing practices," unsanitary surfaces and "direct product contamination." Inspectors also discovered that the farm has had 12 noncompliance records for "findings of fecal material on carcasses" since January 2013.

As part of its decision to keep Foster Farms open Thursday night, USDA officials said they will perform "intensified sampling" of its products for 90 days.

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"All of us at Foster Farms regret any illness associated with our products," Foster Farms President and CEO Ron Foster said in a statement Thursday night. "We have worked relentlessly to address these issues and will continue to do so as we work to regain consumer trust and confidence in the Foster Farms brand. On behalf of everyone at Foster Farms, that is my commitment to you."

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According to Consumer Reports, this chicken is also sold under these brand names: Ralphs, Safeway Farms, Simple Truth Organic, O Organics, Eating Right, Kirkland Signature and Open Nature.

The USDA has advised consumers to check all Foster Farms packages for these numbers: P6137, P6137A and P7632.

ABC News' Gitika Kaul contributed to this report.