McFarland standards

In microbiology, McFarland standards are used as a reference to adjust the turbidity of bacterial suspensions so that the number of bacteria will be within a given range to standardize microbial testing.

Original McFarland standards were made by mixing specified amounts of barium chloride and sulfuric acid together.

Mixing the two compounds forms a barium sulfate precipitate, which causes turbidity in the solution.

The standard can be compared visually to a suspension of bacteria in sterile saline or nutrient broth.

McFarland nephelometer standards:{2} *at wavelength of 600 nm McFarland latex standards from Hardy Diagnostics (2014-12-10), measured at the UCSF DeRisi Lab: Mcfarland Standards-http://www.dalynn.com/dyn/ck_assets/files/tech/TM53.pdf This standards- or measurement-related article is a stub.

McFarland standards. No. 0.5, 1 and 2