Focus on target objects

A sample may contain background particulates, by which we mean objects that are not the intended targets of analysis. For example, a growth medium may include dead cells and residual particulates derived from yeast extracts or similar components. Additional background particulates can originate from compounds added during the drying of bacterial products, such as osmoprotectants, excipients, and bulking agents. Biological matrices like stool and urine samples may also contain background particulates that are not the target objects.

Ensure that you are quantifying the intended target objects rather than background particulates originating from the sample matrix. Whenever possible, include bacteria-free controls to determine whether the background signal is negligible or whether a strategy is required to correct for or subtract background contributions.

Next, we provide a step by step example on testing a growth medium for background particulates. You can apply similar protocols to test osmoprotectants, excipients and bulking agents.

Lastly, we outline mitigation strategies in case of significant particulate background.