I did an experiment using a certain turbidity value (bacteria + medium), in fact another lab send it so to be used, anyway, they did not count the number of colonies. May I use the MCFarland Standard as a similar value? is there any other/better/acceptable way of doing that?
Thanks in advance.
McFarland standard is a method to quickly compare turbidity and for many applications (such as disc susceptibility test) it is reliable enough. As alternative method you may measure OD of your bacterial suspension.
Both methods allows to make your bacterial suspensions similar but it may be necessary to determine CFU/ml.
McFarland standard is a method to quickly compare turbidity and for many applications (such as disc susceptibility test) it is reliable enough. As alternative method you may measure OD of your bacterial suspension.
Both methods allows to make your bacterial suspensions similar but it may be necessary to determine CFU/ml.
Turbidity of microorganisms will be different between one and another depends on particle size and other factors. If you want to get the exact value of the total cell present in a solution I would suggest to use plate count, counting chamber under microscope (haemocytometer), or automatic cell counter. In fact if you want to get the number of living/viable cell, McFarland can not differentiate which cell are living and which are dead. It will only give turbidity of the total cell. So, if you want to get the total living cell, I think McFarland is not the best method. I would prefer Plate count, haemocytometer or automatic cell count. However, if you want to get similar condition between experiments, I guess McFarland is reliable enough, as long as you use cell culture grown in the same media and also same age.
hope this help.
I totally agree with my previous speakers. Therefore, I am using the drop plate method, which is more accurate than the spread plate method. It is also very conveniant and fast.
http://www.ncbi.nlm.nih.gov/pubmed?holding=&cmd=search&term=How+to+optimize+the+drop+plate+method+for+enumerating+bacteria
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