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: Pharmacology
All of the following are therapeutic uses of penicillin G, except - 
Select and explain. 
A. Bacterial meningitis, B. Rickettsial infection, C. Syphilis, D. Anthrax
B: Rickettsial infection
Answer: B: Rickettsial infection 
Explanation: Ans. is 'b' i.e., Rickettsial infection Antibacterial spectrum of Penicillin G (Benzyl Penicillin) o PnG is a narrow spectrum antibiotic o Activity is limited primary to gram positive bacteria (and few others). o Amongst gram negative organisms, penicillin has activity against gonococci, meningococci, few Ecoli & proteus. o Majority of gram negative bacilli are insensitive. o M. Tuberculosis, Ricketsiae, chlamydia, protozoa, fungi and viruses are totally insensitive to penicillin G. Penicillin G is the DOC for (Laurence 9th/e 218. Katzun_g 7301 1. Meningococcal meningitis 7. Leptospira 2. Bacillus anthracis (anthrax) 8. Actinomyces israelii (Actinomycosis) 3. Clostridium perfringens (gas gangrene) 9. Borrelia burgdorferi (Lyme disease) 4. Clostridium tetani (tetanus) 10. Enterococci 5. Corynebacterium diphtheriae 11. Streptococci 6. Treponema pallidum (syphilis) 12. Susceptible pneumococci