Hello,thanks for using Healthcaremagic. i had gone through your query. prognosis of drug sensitive pulmonary tuberculosis is very good, with good compliance to therapy response rate is more than 90 %. as you said your son is respiratory therapist so there is more chance of getting TB from patients at hospital, it is advisable to undergo culture and sensitivity examination at the time of diagnosis itself rather than waiting for 3 months and then retesting again. Culture techniques take time about one month for reporting, as chance of acquiring drug resistant TB is high in hospital setup it is better to do it. give him good diet, daily one egg, one glass of milk. maintain precautions to prevent spread to family members and be compliant with medications. he will get better soon. hope this helps..