Hi. Currently Im working on optimization of OD and cfu of ATCC MRSA and ATCC MSSA. For your information, I have done overnight culture of MRSA and MSSA from glycerol stock and I have subculture them in 1 hour then I have incubate in 37 degree celcius in incubator shaker and I have check the OD every hour. From what I have found, I have get the optimum OD 0.7-0.8 in 4- 5 hours incubation. But when I streaked on TSA to count the cfu, the colonies are too much to count (even for dilution of 10 ^-9).So, how can I troubleshoot to get 10^ 8 cfu? Thanks
Hello Zatie,
OD and CFU dont necessarily exactly correlate. In addition, DO is often a delicate measure that can lead to "paradoxical" results.
I invite you to read my article
"Thierie J. (2014)
A Method for Exploring Suspended Particles Interactions by Means of Optical Density Measurements: Application to Bacterial Floc and Solid Nutrients
J Microb Biochem Technol 6:279-285"
Hope it can help you
PS Do you try a dry weight comparaison?
Are you measuring optical density at 600 nm? As far as I know, for Staphylococcus aureus, OD value of 0.6 at 600 nm correlates with 5 x 10^8 cfu. If you require 10^8 cfu try OD value of 0.5.
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