Weil-Felix reaction uses OX-2, OX-19, and OX-K Proteus antigens for serodiagnosis of rickettsial infections. The agglutination of OX-K strains but not OX-2 or OX-19 suggests infection with:

• A Rickettsia prowazekii (epidemic typhus)
• B Rickettsia rickettsii (Rocky Mountain spotted fever)
• C Rickettsia typhi (murine/endemic typhus)
• D Rickettsia tsutsugamushi (Orientia tsutsugamushi) ✓

Explanation

In the Weil-Felix test, scrub typhus (Orientia tsutsugamushi) gives a positive reaction with OX-K (Proteus mirabilis OXK) but is NEGATIVE with OX-2 and OX-19; epidemic typhus (R. prowazekii) is positive with OX-19 and OX-2; Rocky Mountain spotted fever (R. rickettsii) is positive with OX-19 and OX-2; murine typhus (R. typhi) is positive with OX-19. Q fever (Coxiella) and trench fever (Bartonella) are Weil-Felix negative.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.