Abstract: Methods for detecting one or more target bacteria in a test sample are provided. It is shown herein that photosensitizers combined with intense light exposure reduce fluorescing background due to non-bacterial particles. This permits detection of subsequently labeled target bacterial cells (e.g., using a fluorescently labeled antibody) against a largely black background. In particular examples, the methods include incubating the test sample in a growth medium that permits growth of bacteria present in the sample, contacting the sample with a photo-sensitizer; exposing the sample to light under conditions sufficient for the photo-sensitizer to photobleach contaminating non-bacterial particulates present in the sample. The bacteria can then be substantially separated from the sample, thereby generating an isolated bacterial sample. The method can also include contacting the isolated bacterial sample with a binding agent specific for the one or more target bacteria, and detecting the one or more target bacteria.