The worldwide spread of antibiotic-resistant bacteria poses a global threat to human health which must be addressed at multiple levels. 1-3 While developing new antimicrobials is resourceintensive and slow, new sensors and assays are required for fast and sensitive detection of bacteria in biological samples as an essential strategy for preventing and managing bacterial infections. Such sensors and assays would be of great practical utility in clinical laboratory diagnostics, fundamental biomedical research on host-pathogen interactions, environmental and quality control testing, and other applications. Ultimately, such sensors could moderate the overuse of antibiotics and alleviate the spread of antibiotic resistance. 4-11 Biosensing platforms based on fluorescence readout offer distinct advantages owing to the possibility for rapid analysis, high sensitivity, facile multiplexing, and compatibility with live cells and tissues. In addition, fluorescence analysis can be performed using various instruments, including portable devices for point-of-care diagnostics. Given that, bacteria-specific fluorescent molecular probes have received substantial attention as prospective bioanalytical tools for fundamental research and clinical diagnostics and imaging. 12-17 A key advantage offered by the technology of fluorescent molecular probes is the possibility of combining desired optical properties with high target selectivity, high signal-to-noise ratios, and low detection limit by tailoring the molecular architecture of the probe. In this context, fluorogenicity refers to the ability of a probe to exhibit enhanced fluorescence upon interaction with the target as compared with the free probe in solution. 18-20 Rationally designed fluorogenic molecular probes are well suited for detecting low-abundance targets with high signal-to-noise ratios in biological samples. 21-23 Ideally, the assay should be performed with minimal sample processing in an "add-and-read" format.

In the field of bacterial pathogen detection, fluorescent and especially fluorogenic probes hold great promise compared to conventional microbiological assays. 13-16,24 The conventional assays based on microbial culture or nucleic acid detection techniques are indirect, timeconsuming, and labor-intensive. 25 Contrary to that, bacteria-specific fluorescent probes are designed for direct staining of bacteria in the sample, enabling fast and sensitive detection of pathogens in complex media. Fluorescent probes could shorten the analysis time and increase the throughputness and cost-effectiveness of bacteria-detection assays.