A third sputum test on a man quarantined with a dangerous strain of tuberculosis was negative for the presence of TB bacteria, hospital officials said Tuesday, opening up the possibility that he could be briefly allowed out of isolation.

The tests results mean Andrew Speaker is considered to have a relatively low chance of spreading the disease, given certain precautions, doctors said.

Normally, TB patients with three negative sputum tests who have undergone two weeks of treatment are allowed to leave their isolation room for short periods as long as they wear a mask. No decision has been made yet on when Speaker will be able to leave his room, said William Allstetter, a spokesman for National Jewish Medical and Research Center.

Allstetter had cautioned previously that although a third negative test result would mean Speaker was "relatively noncontagious," it would not mean that Speaker cannot transmit the disease because the bacteria could still grow in his lungs and sputum.

Doctors are hopeful Speaker's tuberculosis can be cured because it is not widespread, he is otherwise healthy and young, and his hospital has extensive experience in removing stubborn, drug-resistant infections.

"He has a number of features that make us optimistic about the potential outcome of his treatment," said Dr. Michael Iseman, senior staff physician at National Jewish Medical and Research Center.

The negative test result means no germs were visible in a sputum sample. However, a culture test has yielded TB bacteria. That laboratory test was performed in Georgia, where after a few weeks germs replicated and were visible in Speaker's sputum, according to Dr. Michael Iseman of National Jewish.

Iseman said other factors — including whether other people have weakened immune systems — also contribute to whether Speaker can spread the disease.

Speaker, 31, an Atlanta lawyer, was initially found to have multidrug-resistant TB, which can withstand two mainline drugs used to treat tuberculosis. While he was in Europe on his honeymoon last month, tests revealed he had extensive drug-resistant tuberculosis, or XDR-TB, which can withstand more drugs.

Speaker's TB was caught early by chance in January when he had a chest X-ray for a rib injury. Otherwise, he hasn't shown any symptoms of the disease — coughing, loss of weight or a fever.

Speaker's strain has so far resisted at least 10 of 14 drugs available for treating TB, according to tests performed in Georgia, Iseman said. Surgery to remove infected lung tissue, about the size of a tennis ball, is one option. The infection's relatively small size increases the chances of success of surgery.

Surgery to eradicate TB is one of National Jewish's specialties, noted Dr. Neil Schluger, a professor of medicine at Columbia University Medical Center.

"In particular, they've had more experience operating on patients with drug-resistant TB than just about any other hospital in the United States," Schluger said.

A study of 205 patients treated for multidrug resistant TB at National Jewish between 1983 and 1998 showed that those who underwent surgery had a 90 percent cure rate, Iseman said. About 20 of those patients are believed to fall into the newly created XDR category, and doctors are trying to find cure and survival rates for those patients, he said.

Of all 205 patients, 9 percent died of TB, Iseman said.