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 quite pathogenic for their natural hosts. Serologic reactivity is predominantly directed against either rLPS or sLPS components. Our IFA slides use both Brucella abortus and Francisella tularensis. Brucella and Francisella show occasional cross-reactivity and can be cross-absorbed when necessary.