It usually takes about a week to determine if a person has TB, but it can take longer in certain situations, officials said.
Parker said one reason it took longer to make a determination was because samples analyzed at the state Public Health Lab in Baltimore were negative. Officials then had to grow cultures from samples taken at a hospital where the initial test was done, said Parker.
"The case is basically closed," said Parker.
Officials have told the teacher, who was not identified, that he can return to work, Parker said. The teacher was off while additional tests were conducted.
Family members and people with whom the man was in close contact at the Career Studies Center already have been tested, and showed negative for the disease, Parker said. About 342 students attend vocational classes at the school on Oak Ridge Drive.
Tuberculosis is an infectious disease that in humans usually spreads through the air. People stricken with TB may complain of feeling sick or having a fever and night sweats.
The disease can cause permanent damage to the body and death if left untreated, officials said. Antibiotics are used to fight TB, and the cure rate is very high, officials said.