Proteus antigen cross react with:
Klebsiella
Chlamydiae
Rickettsiae
E. coli
Ans. 'c' i.e., Rickettsiae(Ref: Ananthanarayan, 9th/e, p. 410)Proteus antigens (OX19, OX2, OXK Strains) cross reacts with group specific alkali stable lipopolysaccharide rickettsial antigens. The application of this property is done in the Weil Felix (heterophile agglutination) test.
Bacteria