A National Institutes of Health employee pleaded not guilty Wednesday to allegations she made an anthrax threat against a county agency during a tax dispute.

Michelle Ledgister, 43, faces as many as five years in prison and a $250,000 fine if convicted under an anti-terrorism law making it a federal crime to falsely threaten someone with anthrax spores.

Ledgister works at the National Institute for Allergy and Infectious Diseases in Bethesda as a public health program analyst, according to the NIH. She does not have access to dangerous biological agents, spokesman Don Ralbovsky said.

The Broward County property appraiser's office revoked a tax break for a house Ledgister owns in Parkland, effectively raising her annual taxes by about $2,300.

The office determined that Ledgister, who lives in Silver Spring, did not qualify for the state homestead exemption because her Florida house was rented.

According to the FBI, Ledgister called the appraiser's office on July 26, identified herself and said, "You guys now have anthrax spores once again, so do be careful."

She is charged under a federal law passed partly in response to the 2001 mail anthrax attacks, which killed five people -- including a tabloid photo editor in Boca Raton, Fla., -- and sickened 17 others. No one has been charged in those attacks.

Ledgister and her attorney would not comment after Wednesday's hearing. U.S. Magistrate Judge Edwin Torres set another hearing for Sept. 8.