Undulant fever is caused by: (A) Salmonella typhi, (B) Staphylococcus aureus, (C) Brucella melitensis, (D) Coxiella burnetti
Answer is C. 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