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: Microbiology
In patient with Listeria meningitidis who is allergic penicillin the treatment of choice is: 
Select and explain. 
A. Vancomycin, B. Gentamycin, C. Trimethoprim - sulfamethoxazole, D. Ceftriaxone
C: Trimethoprim - sulfamethoxazole
Answer: C: Trimethoprim - sulfamethoxazole 
Explanation: Ans. (c) Trimethoprim - sulfamethoxazole DOC for listeriosis (non-pregnant, neonate, pregnant) is ampicillin or penicillin often in combination with aminoglycosides. During last month of pregnancy (in case of penicillin allergy), may be treated with erythromycin. Otherwise in all cases of penicillin allergy DOC is trimethoprim-sulfamethoxazole