Hi welcome to Health care magic forum. You have mentioned, that the boy is on ATT but didn't mentioned the drugs. whether two drugs or more. In case if 2 drugs 3or 4 drug regimen may help for complete cure. Sometimes adding a general antibiotic may help complete cure. Anaemia
or some general conditions may obstruct the cure.
Besides i advise you some diet recommendations to the mother if breast feeding. Take more of greeny vegetables, pulses, sprouts, milk, egg, meat, fruits, juices, sea foods and dry fruits. To increase the mother and childs blood, general health and resistance to combat such infections.
Wishing for a quick recovery and thanks for calling.