Synergistic action is shown by all except
?
a) Penicillin plus sulfonamide
b) Streptomycin plus tetracycline
c) Rifampicin plus dapsone
d) Penicillin plus tetracycline
Correct Answer - D
Ans. D. Penicillin plus tetracycline
Combination of a bactericidal with a bacteriostatic drug may be
synergistic or antagonistic depending on the organism.
If the organism is highly sensitive to the cidal drug - response to the
combination is equal to the static drug given alone (apparent
antagonism), because cidal drugs act primarily on rapidly multiplying
bacteria, while the static drug retards multiPlication.
This has been seen with penicillin + tetracydine/chloramphenicol on
pneumococci which are highly sensitive to penicillin.
Pneumococcal meningitis treated with penicillin + tetracycline had
higher mortality than those treated with penicillin alone.
Penicillin + erythromycin for group A Streptococci and nalidixic acid
- nitrofuration for E. coli have also shown antagonism.