Follow-up tests on a Tulane National Primate Research Center worker who previously tested positive for exposure to deadly bacteria that escaped from the center’s lab have shown that the worker was not exposed while at the center, a Tulane spokesman said Wednesday.

The worker — whose initial test results barely registered as a positive for exposure to Burkholderia pseudomallei, which can cause the disease melioidosis — may have been exposed elsewhere, according to Tulane University spokesman Michael Strecker.

In addition, one of eight monkeys that previously tested positive for exposure was retested and found not to have been exposed, Strecker said.

Three of the eight monkeys thought to have been exposed were infected with the bacterium and eventually euthanized. The other five had antibodies in their blood consistent with exposure, but they have yet to develop any signs of illness.

The center has been the subject of a federal investigation since December after the bacterium — classified by the federal government as a “select agent,” or one that could pose a severe threat to human, animal or plant health — escaped from what is supposed to be a highly secure lab and infected two monkeys.

A report last week from the federal Centers for Disease Control and Prevention found that employees frequently neglected to wear the proper personal protective equipment when they entered the lab, and when they did wear the right gear, they sometimes wore it incorrectly.

The bacteria could have been carried on clothing to the lab’s veterinary clinic, where all eight of the monkeys were treated at some point, CDC officials said.

All of the Tulane center’s research into select agents has been suspended by order of the CDC.

Before the work can begin again, Tulane will have to submit a corrective action plan along with a timeline for implementing those actions. Officials from the CDC and the U.S. Department of Agriculture will review the plan; if it is deemed acceptable, Tulane will be able to implement it, according to Jason McDonald, a CDC spokesman.

Creating new policies on the use of protective gear and retraining staff are among the corrective actions Tulane will have to take, officials have said. The changes could take months to implement.

The USDA is continuing to work with primate center officials to test monkeys and local wildlife for Burkholderia pseudomallei exposure and infection as well as to monitor the nearby soil and water — the bacterium’s normal home — for possible contamination.

Burkholderia pseudomallei is native to southeast Asia and Australia.

Infection can occur when a person comes into direct contact with the bacterium, often through touching contaminated soil or drinking contaminated water. The resulting disease, melioidosis, can be difficult to diagnose, but it can be treated with antibiotics.

The latest announcement reduces the number of exposed monkeys to seven. Several hundred monkeys’ samples are being tested. No humans have been confirmed for exposure to the bacterium, officials said.

Throughout the entire process, the CDC has said no evidence has been found of a threat to public health outside the center.

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