McFarlandBSS0.5

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 10⁸ 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.

The McFarland BSS Standards are used as turbidity standards since 1907 to produce an expected reproducible cell density of a bacterial suspension.