"What that means is that when he coughed up a specimen to give to the doctors to test for TB, the laboratory looked under the microscope [and] they didn't see any TB bacteria. It was only when [the SAMPLE] was cultured that then they figured out, 'Oh, there REALLY is TB here' and then it took some weeks to figure out it was drug resistant," says Hamilton.

In contrast, smear-positive TB patients "have so much TB in their lungs that when the laboratory looks DIRECTLY into the microscope, they can see the bacteria right there. Those people tend to be a lot more infectious or contagious to OTHERS than someone who really has disease but doesn't yet have enough built up that they're really coughing out a whole lot at a time."

When TB bacteria keep GROWING, eventually "you can see it under a microscope, and that's associated with easily infecting other people," Hamilton says.

"What that means is that when he coughed up a specimen to give to the doctors to test for TB, the laboratory looked under the microscope [and] they didn't see any TB bacteria. It was only when [the sample] was cultured that then they figured out, 'Oh, there really is TB here' and then it took some weeks to figure out it was drug resistant," says Hamilton.

In contrast, smear-positive TB patients "have so much TB in their lungs that when the laboratory looks directly into the microscope, they can see the bacteria right there. Those people tend to be a lot more infectious or contagious to others than someone who really has disease but doesn't yet have enough built up that they're really coughing out a whole lot at a time."

When TB bacteria keep growing, eventually "you can see it under a microscope, and that's associated with easily infecting other people," Hamilton says.