This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
Undulant fever is caused by 
Select and explain. 
A. Salmonella typhi, B. Staphylococcus aureus, C. Brucella melitensis, D. Coxiella burnetti
C: Brucella melitensis
Answer: C: Brucella melitensis 
Explanation: Acute brucellosis is mostly due to B.melitensis. It is usually known as undulent fever, but this is misleading as only some cases show the undulent pattern. It is associated with prolonged bacteremia and irregular fever. Ref: Textbook of microbiology; Ananthanarayan and paniker's; 10th edition; Pg:347