The cell density is adjusted in the simple comparison to the standard. This can be directly performed visually or by measuring with a spectrophotometer. The turbidity value of the standard of 0,5 MFU (McFarland Units) corresponds to approximately a culture density of 1,5 x 10 8 cells/ml. This cell density is specially needed as bacterial inoculum for the antibiotic susceptibility test. The absorption is measured at a wavelength of 625 nm. McFarland PMS 0.5 for microbiology The McFarland PMS Standards are equivalent turbidity standards to the original barium sulfate standards. The optimised Polymer Microparticle Suspension (PMS) separates slower than the barium sulfate version. Not a medical device / Not an IVD product