Phage therapy is the use of bacterial viruses, or bacteriophages, as antibacterial agents. It has been in use for over 100 years and is becoming increasingly common clinically. The first steps of phage therapy include identification of bacteria to be targeted and then obtaining phages with appropriate host ranges. This is followed by various approaches to in vitro phage characterization. Increasingly common for phage phenotypic characterization is the use of kinetic microtiter plate readers. They can both decrease workloads and increase throughput, especially relative to analyses that require plating on agar-based media. These colorimetric/turbidimetric/optical density approaches primarily assess phage-induced culture-wide bacterial lysis, in the shorter term, or instead the phage potential to suppress phage-resistance evolution over longer time frames. Considered here are methods relevant to phage characterization especially for phage-therapy purposes. Discussed are turbidity-reduction assays, determinations of phage antibacterial virulence, and related time-kill curve analysis. All are or can be optical density-based approaches to assessing phage-based bacterial reduction. Emphasis is placed on consideration of the utilities, limitations, and intersections of these similar methods. Emphasized is that the start of “Deviation”—where phage-treated culture turbidity diverges from phage-free controls—may represent a superior endpoint for such optical density-based bacterial-reduction protocols.

Scientists have advanced the field of cancer treatment by leveraging the body’s immune system to recognize and target tumors. The study of the immune system helps better advance these treatments and boost immune responses. The evolution of immune cells and different aspects of the immune system has helped fight aggressive forms of disease. More importantly, as ancient populations become exposed to different diseases over time, heredity can protect future generations from these specific viruses and bacteria.

One specific part of the immune system, known as ‘complement’, is crucial to aiding a robust immune response. Complement is part of the innate immune system and consists of over 50 plasma proteins. Complement proteins rapidly target foreign pathogens and trigger inflammation from infection. Specifically, these proteins help puncture infected cell membranes to eliminate disease. While complement is a unified system, it takes several pathways to function: Classical, Lectin, and Alternative. These three functions trigger complement in different ways but converge into a single innate immune defense. There are also different types of complement proteins. One of the most abundant is complement C3, which acts as a critical surveyor and defense against pathogens. Compliment C3 is an ancient protein and is found in organisms such as jellyfish, playing a pivotal role in the immune system. It specifically tags infected cells with molecules for immune cells to identify and target.