Question
A: Culture negative endocarditis is seen in infection caused by Coxiella burnetti. R: All culture negative endocarditis are due to prior antibiotic exposure.
Answer
- [x] c) A is true but R is false
Assertion is true: Coxiella burnetii (the causative agent of Q fever) is indeed a well-recognized cause of culture-negative infective endocarditis, since it is an obligate intracellular organism that does not grow on standard blood culture media, requiring specialized serological (phase I/II antibody) or molecular diagnosis instead. Reason is false: it is not true that all culture-negative endocarditis is due to prior antibiotic exposure — while prior antibiotic treatment is indeed one important and common cause of culture-negative endocarditis (by suppressing bacterial growth before blood culture is obtained), a significant proportion of culture-negative endocarditis cases are due to fastidious or intracellular organisms that simply do not grow on routine culture media regardless of antibiotic exposure — including Coxiella burnetii, Bartonella species, Tropheryma whipplei, and the HACEK group of organisms (which grow poorly/slowly). Therefore, the reason’s absolute/universal claim (“all”) is incorrect, making it a false statement despite the assertion itself being true.