I have grown a bacterial isolate (using 0.5 Mcfarland standard) in an antibiotic microplate and took the optical density (OD) dynamically for 48h.
From the microplate reader, the OD for growth curves did not all start from zero (varied widely) and some growth curves susceptible to antibiotics were above growth control (GC-growth without antibiotics), though flat. Is there a particular growth equation or normalization for OD data (apart from natural log)? In summary, blank-corrected OD data not starting from zero or growths susceptible to antibiotics were above GC, see image below.
Any help will be appreciated.
Thank you.
Philips
Obviously when you are starting with an initial OD reading for your samples of nearly 1.0 then you are not going to see any growth. I imagine the problem has something to do with either the blanks, or the medium, the plates, or something systematic like that. What wavelength are you measuring at? What happens if you blank first with water and then just measure medium?
Bacterial grow and change of turbidity of liquid media can be directly expressed by OD. You need to measure OD every 2hour during incubation for creating correlation between OD and CFU/ml .
The CFU/ml of initial or intermediate grow can be counted by performing grow of decimal dilution of same sample. You can use the formula for evaluation your data.
Good luck
For my growth assays with E. coli strains, stating OD is at approximately at 0.05. when cultures reach an OD of 1-2 they are almost at stationary phase and I stopped taking the readings. Maybe your blank or antibiotic cultures were contaminated as the starting OD is quite high. I am wondering if this is a one-off or have you observed this repeatedly? Also what OD reading was used
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