McFarland standards

McFarland standards are prepared reference solutions used in microbiology to estimate the concentration of bacteria in a sample. They provide a visual benchmark—based on turbidity or cloudiness—that helps scientists standardize bacterial concentrations for accurate testing and comparison. For example, a McFarland standard with a specific turbidity corresponds to a known number of bacteria per milliliter, ensuring consistent sample densities across experiments. This helps in identifying bacteria, testing antibiotics, and conducting research with reproducible and reliable results.