Antigen used in Weil-Felix reaction:

Ans. c (Proteus). (Ref. Textbook of Microbiology by Ananthnarayan, 7th/283)PROTEUS# Normal intestinal commensals and opportunistic.# Proteus mirabilis is the most important urinary and nosocomial pathogen.# Gram-negative, motile, pleomorphic, and non-capsulated rods.# Lactose non-fermenter; Urease producing; Phenylalanine deaminase +# "Swarming growth" with fishy/seminal odour.# Most strains are lactose negative, produce H,S, and demonstrate characteristic swarming motility on agar plates. P mirabilis is indole negative, whereas P. vulgaris and P. penneri are indole positive.# Certain non-motile proteus vulgaris strains (X strains) agglutinate by sera from typhus fever patients (heterophilic agglutination reaction) - basis of Weil-Felix reaction for diagnosing Rickettsial infections.# Strains 0X2, 0X19, OXK are used in agglutination test.# Alkalization of urine, in turn, leads to precipitation of organic and inorganic compounds, with the formation of struvite and carbonate-apatite crystals, the formation of biofilms on catheters, and/or the development of calculi.# Rx:- P. mirabilis is susceptible to most antimicrobials except tetracycline, polymyxin B, and tigecycline.- 4th-gen cephalosporins (eg.cefepime), amikacin, TMP-SMX have excellent activity against Proteus.The urinary tract is by far the most common site of Proteus infection, with adhesins, flagella, IgA protease, and urease representing the principal urovirulence factors.