Social & Preventive Medicine For sputum smear to come positive on ZN staining there should be minimum:- A 100 bacilli per per ml sputum B 1000 bacilli per ml sputum C 2000 bacilli per ml sputum D 10,000 bacilli per ml sputum 💡 Explanation For sputum smear to come positive on ZN staining there should be minimum:- ✓ Correct Answer: D. 10,000 bacilli per ml sputum