High-contrast imaging of cellular non-repetitive drug-resistant gene via in situ dead Cas12a-labeled PCR In situ imaging of genes of pathogenic bacteria can profile cellular heterogeneity, such as the emergence of drug resistance. Fluorescence in situ hybridization (FISH) serves as a classic approach to image mRNAs inside cell, but remains challenging to elucidate genomic DNAs and rely on multiple fluorescently labeled probes.