A second monkey infected with the Burkholderia pseudomallei bacterium at the Tulane National Primate Research Center in Covington has been euthanized, officials said Friday.

The monkey, one of the first two infected with the bacterium, was put to death Thursday after veterinarians decided its symptoms — diminished appetite, skin ulcerations and testicular swelling — were too severe to be treated with another round of antibiotics, according to a news release from St. Tammany Parish spokesman Ronnie Simpson.

Two monkeys showed signs of infection in November. One was euthanized at that time, but the other, known as IB22, was treated with antibiotics and was believed to have recovered, officials said in mid-January.

IB22’s last course of antibiotics concluded Jan. 5 and the monkey was being monitored in the center’s hospital when the new symptoms appeared, the release said.

At times, a recurrence of the disease can be seen after a round of antibiotics has been completed, Tulane spokesman Michael Strecker said.

Two other monkeys have shown immune responses consistent with exposure to Burkholderia pseudomallei, though neither has been diagnosed with melioidosis, or Whitmore’s disease, which is caused by the bacterium.

The only place those two monkeys came into contact with the original two infected monkeys was at the center’s veterinary clinic, and the investigation into how the bacterium escaped tight controls in the center’s lab has subsequently focused on the clinic.

Burkholderia pseudomallei is native to southeast Asia and Australia, where it is most often found in contaminated soils and water. Infection happens when people inhale dust or water droplets containing the bacterium, drink contaminated water or come into direct contact with the bacterium in the soil. The disease is treatable with antibiotics.

Burkholderia pseudomallei is classified by the federal government as a “select agent,” one that could pose a severe threat to human or animal health or animal or plant products. Other select agents include ricin, anthrax and bird flu.

Once the monkeys’ infection became known, the federal Centers for Disease Control and Prevention ordered the Tulane center to suspend its work with all select agents. Scientists at the center have done research on HIV/AIDS, tuberculosis and Lyme disease, among others. The center is known as a hub of infectious disease research.

A U.S. Agriculture Department investigator who was at the center in January to look into the monkeys’ infection reported symptoms consistent with the disease, but later tests indicated her exposure to the bacterium probably was not recent.

Tests of the air, water and soil at the Primate Research Center have been negative for the bacterium, Strecker said Friday.

Follow Faimon A. Roberts III on Twitter, @faimon.