Brucellae are facultative-intracellular zoonotic pathogens. Although smooth LPS forms (Brucella abortus, B. melitensis and B. suis) are major human pathogens, rough LPS forms (B.canis and B.ovis) are only pathogenic for their natural hosts. Serologic reactivity is predominantly directed against either rLPS or sLPS components. Our IFA test uses B. ovis to detect reactivity against both B. canis and B. ovis, while our FT-12 IFA slides use both Brucella abortus and Francisella tularensis. Occasional sera show cross-reactivity between Brucella and Francisella and can be cross-absorbed when necessary.