A third test of Andrew Speaker's sputum turned up negative for the presence of TB bacteria, confirming the results of earlier tests at National Jewish Medical and Research Center.

Normally, TB patients with three negative sputum tests who have undergone at least two weeks of treatment are allowed to leave their isolation rooms briefly as long as they wear a mask. Additional precautions are advised for patients, like Speaker, with drug-resistant strains of the disease.

"Mr. Speaker's case is extraordinary, and no decision has been made about when he will be able to leave his isolation room," hospital spokesman William Allstetter said in a statement.

Doctors are hopeful Speaker's tuberculosis can be cured because it is not widespread, he is otherwise healthy and young, and National Jewish has extensive experience treating drug-resistant infections with a combination of drugs and surgery.

Speaker, 31, originally was 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.

A smear test is one way to test for the presence of TB bacteria and requires patients to inhale an irritating salt water solution, producing a deep cough. Their mixture of saliva and phlegm is then smeared on a slide and placed under a microscope.

A negative result means there were no germs visible. But a culture test of Speaker's sputum — considered the "gold standard" in TB testing — has yielded TB bacteria.

Allstetter cautioned that a patient with a negative smear test could still have TB bacteria in his sputum, and cited a recent study suggesting that 20 percent of new TB cases could be traced back to contact with smear-negative patients.

Tuberculosis is transmitted by air in nearly all cases. Active TB patients normally cough, dispersing particles that can float in the air for hours. Speaker does not have a cough, Allstetter said.

Health authorities are still trying to contact passengers and crew members who were aboard two trans-Atlantic flights with Speaker last month to advise them to undergo TB testing.