VPT-0003
QUESTION
Of the following the best first antimicrobial agents to treat septicemia in a newborn foal would be?
OPTIONS
(A) Penicillin and Gentamicin sulphate
(B) Trimethoprim and sulfadiazine
(C) Sodium ampicillin and streptomycin
(D) Chloramphenicol
ANSWER
(B) Trimethoprim and sulfadiazine
EXPLANATION
Trimethoprim and sulfadiazine are used together because they inhibit two successive steps in bacterial folic acid synthesis, producing a synergistic, broad-spectrum antibacterial effect. This makes the combination suitable for initial treatment of septicemia in a newborn foal, which may involve different Gram-positive and Gram-negative bacteria. Penicillin and gentamicin can also be used clinically, but gentamicin may cause nephrotoxicity, particularly in compromised or dehydrated foals. Sodium ampicillin and streptomycin is less preferred because streptomycin has greater toxicity and less reliable activity, while chloramphenicol is avoided because of its toxicity and adverse effects.