The VAST majority of TB detected in screening PPDs is latent TB. That basically means it is not actively causing infection and can't be transmitted to others. The standard of care is 6-9 months of Isoniazid. Then you are essentially 'cured.' Even without the Isoniazid ~90% of people with latent TB will never convert to active TB.
Active TB is very different from latent TB. Active TB means you are actually sick. Cough, night sweats, feel crappy, etc. Active TB would put you out of work because you could transmit it to others. That requires a three drug regimen (sometimes 4) and isolation.
People in their 20s are unlikely to have active TB unless they are immunocompromised due to HIV/AIDs or something like chronic steroid use.
Also FYI --- Latent TB found on PPD is way more common than you think. As a med student I have been exposed to multiple patients with TB (before they were in isolation) and know several nurses who ended up being treated for latent TB. If you work in a urban hospital or anywhere near the US-Mexico border you will likely be exposed to patients with active TB multiple times a year. It's a risk that goes with being a healthcare worker.