Compositions and methods for detecting Yersinia pestis bacteria

A method for determining the presence or absence of bacteria of a target bacterial type in a sample, comprising

• (i) contacting the sample with genetically modified bacteriophage that are selective for the target bacterial type under conditions that allow said genetically modified bacteriophage to infect said bacteria of the target bacterial type that may be present in said sample, thereby producing a bacteriophage exposed sample, wherein said genetically modified bacteriophage comprise a recombinant bacteriophage marker gene comprising a nucleic acid sequence encoding a bacteriophage marker operably linked to an expression control region that affects expression of said bacteriophage marker gene during the late eclipse or early latent period following infection of said bacteria of the target bacterial type by said genetically modified bacteriophage and results in overexpression of the bacteriophage marker gene;
• (ii) incubating said bacteriophage exposed sample for a period of time sufficient to allow said genetically modified bacteriophage to infect said bacteria of the target bacterial type that may be present in said sample;
• and
• (iii) assaying said bacteriophage exposed sample for the bacteriophage marker encoded by said bacteriophage marker gene to detect the protein expressed from the bacteriophage marker gene, wherein said assaying step does not detect the presence of said bacteriophage marker in the bacteriophage exposed sample in the absence of bacterial infection, and wherein the presence of said bacteriophage marker indicates the presence of said bacteria of the target bacterial type in said sample,
• wherein said nucleic acid sequence encoding a bacteriophage marker encodes an endogenous head assembly protein, and wherein said expression control region affects overexpression of said bacteriophage marker gene encoding said endogenous head assembly protein,
• wherein said bacteriophage marker encoded by said bacteriophage marker gene is not accessible for detection on intact progeny phage, and
• wherein said target bacterial type is Yersinia pestis, and
• wherein said endogenous head assembly protein is the 15.8 kDa φA1122 head assembly protein.