A patient from a rural area presents with high fever, severe headache and an eschar on the leg. The Weil-Felix reaction shows agglutination with Proteus mirabilis OXK strain at a titre of 1:320. This result supports the diagnosis of:
- A Murine typhus
- B Epidemic typhus
- C Scrub typhus ✓
- D Q fever
Correct answer: C. Scrub typhus
Explanation
The Weil-Felix test exploits cross-reactivity between rickettsial antibodies and somatic O antigens of Proteus species. Orientia tsutsugamushi, the agent of scrub typhus, cross-reacts with the OXK strain of Proteus mirabilis. OX19 positivity suggests epidemic or murine typhus (Rickettsia prowazekii or typhi), while OX2 suggests spotted fever group. Q fever caused by Coxiella burnetii does not give a positive Weil-Felix reaction at all because Coxiella lacks the cross-reactive antigens.
Reference: Ananthanarayan and Paniker Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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