Abstract: Methods of detecting target bacteria are provided. In some embodiments the methods comprise exposing the sample to a phage capable of infecting a set of target bacteria and comprising a heterologous nucleic acid sequence encoding a marker. In some embodiments the target bacteria comprise Listeria. In some embodiments the target bacteria are all Listeria. Recombinant Listeria phage comprising a heterologous nucleic acid sequence encoding a marker are also provided as are useful combinations of such phage and articles of manufacture comprising such phage, among other things.