An international consortium of researchers has devised a novel strategy for developing rapid, inexpensive diagnostic tests for microbial infections.

Effective treatment of microbial infection is critically dependent on early diagnosis and identification of the causative organism. One inexpensive, rapid and adaptable to point-of-care diagnostic method is immunoassay for microbial antigens that are shed into bodily fluids during infection. A major barrier to developing these diagnostics is determining which of the hundreds or thousands of antigens produced by the pathogen are actually present in patient samples in detectable amounts.

Using a technique they call In vivo Microbial Antigen Discovery (InMAD),the researchers amplifed the small signals present in an infected mouse's blood by purifying serum samples and using them to immunize another mouse. The resulting "InMAD immune serum" from the second mouse, which contains antibodies specific for the soluble microbial antigens present in sera from the infected mice, is then used to probe blots of bacterial lysates or bacterial proteome arrays. 

The spots on the blot or the array that light up indicate the antigens to which the mouse immune system reacted. These are the antigens that could be targeted in an immunoassay. 

Using the InMAD system, they successfully identified antigens that could be used in rapid diagnostics for the biothreats Burkholderia pseudomallei and Francisella tularensis.

The research was published in mBio, an open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. 