This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Which of the following is not a bactericidal agent? 
Select and explain. 
A. Rifampicin, B. INH, C. Pyrazinamide, D. Ethambutol
D: Ethambutol
Answer: D: Ethambutol 
Explanation: Rifampicin is bactericidal and effective against extracellular and intracellular bacilli. INH is also effective against both intra and extracellular bacilli. It is more effective on rapidly multiplying bacilli. Pyrazinamide is effective against the slow multipliers. Ethambutol is bacteriostatic. Remember: Streptomycin is bactericidal Thiacetazone is bacteriostatic Ref: Park, 21st Edition