C. burnetii is best described as which type of organism?

• A. Obligate intracellular coccobacillus
• B. Facultative intracellular coccobacillus
• C. Facultative extracellular cocci
• D. Obligate extracellular bacillus

Answer: (B)

Coxiella burnetii is best described by its ability to replicate inside host cells while also being cultivable outside cells under appropriate lab conditions. It is a small Gram-negative coccobacillus that many times lives within macrophage phagolysosomes, but it can be grown in cell-free, specialized media, showing it isn’t restricted to an intracellular lifestyle. This combination—intracellular replication with potential for cell-free growth—fits the label of facultative intracellular and aligns with its coccobacillus shape, not cocci or a purely extracellular organism.