Abstract: There is provided a method of selecting an anti-macrophage micro-organism comprising an anti-macrophage factor, the method comprising the steps of: a) obtaining an assay micro-organism and preparing a sample thereof; b) lysing the assay micro-organism cells contained in the sample from (a) to form a lysate fluid; c) contacting a sample of macrophage cells with the lysate fluid from step (b); d) determining the macrophage cell viability and comparing the viability to the viability of macrophage cells in a control macrophage sample; and e) selecting the micro-organism as an anti-macrophage micro-organism if the viability is reduced by at least 10%. The anti-macrophage factors identifiable by methods according to the invention can be used in the formulation of vaccines and other therapies against disorders caused by the anti-macrophage micro-organism.