Bacteriophage can be described as bacteria-specific viruses. Unlike viruses, bacteriophages are safe to humans, animals, and anything that is not bacteria. Bacteriophages have evolved to replicate efficiently on specific bacteria.
MicroPhage's technology represents a well-defined approach to identifying pathogens quickly. Specific bacteriophage are introduced to the sample, where they find, infect and amplify on their target pathogen(s). This process provides a very specific, highly amplified surrogate marker for rapid detection.
Bacteriophages selectively infect targeted bacteria and multiply at rates 50 to 200 times that of the bacteria themselves. In hours, tens to thousands of progeny phage are produced for every bacterial cell. Increasing pressure within the bacterial cell causes it to burst, releasing the progeny phage. These progeny phage go on to infect other bacteria, and the cycle repeats.
The increase in bacteriophage concentration indicates the presence of the target bacteria. The faster multiplication rate reduces incubation time, resulting in complete assay times of three to five hours compared with traditional culture assay times of 24 to 48 hours.
To determine antibiotic susceptibility/resistance, the bacteria are exposed to the bacteriophage plus the target antibiotic. Since bacteriophage amplification requires a viable, replicating bacterial host, susceptible organisms die or cannot support phage amplification. Resistant bacteria will produce a bacteriophage signal, but susceptible phages do not, allowing resistant and susceptible strains to be differentiated.
The phage life cycle
MicroPhage uses the well-defined life cycle of lytic bacteriophage to detect target bacteria.
Bacteriophage quickly find specific receptors on the surface of the target bacteria and attach in a two-step process. First, the phage tail fibers create a low-affinity bond to the outer membrane of the bacterium. Second, small tail fibers extend from the baseplate of the bacteriophage to form a high-affinity, irreversible bond to the bacterium. Enzymes located on this baseplate allow the softening of the bacterium's membrane.
Once the phage creates an irreversible bond to the bacterium and the enzyme has sufficiently compromised the membrane, the phage injects its nucleic acid into the bacterium. The bacteriophage's nucleic acid inserts itself into the DNA replication process of the bacterium host, halting further bacterial growth and forcing it to produce proteins that will assemble and become bacteriophage.
By hijacking the host cell's biosynthetic machinery, the phage replicates inside the host cell, producing thousands of progeny phage.
Depending on the bacteriophage, an additional enzyme is formed following, or in concert with, bacteriophage replication. This step produces holin or lysin, which thins the bacterial membrane and allows the progeny phage to break into the open environment.
This step occurs for each successfully infected bacterium. With high concentrations of bacteria, lysis will occur almost in unison for all phage-infected bacteria.