I need a reference paper for the below-mentioned CFU formula? Thanks in anticipation.
Colony-forming unit (CFU) ml-1 soil = Number of colonies × Dilution factor
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Volume of culture plate (inoculum)
I guess this reference is suitable.
I assume that you plate 1 ml of each solution; if not, volume of inoculum must be considered. Indeed, if you plate duplicate plates or serial dilutions, data from duplicates or other dilutions must be considered too
https://www.fda.gov/food/laboratory-methods-food/bam-chapter-3-aerobic-plate-count
This document is free access. Have a look at the Conventional Plate Count Method section
You can cite as FDA, Maturin, LJ and JT Peeler, “Chapter 3: Aerobic Plate Count,” Bacteriological Analysis Manual, https://www.fda.gov/food/laboratory-methods-food/bam-chapter-3-aerobic-plate-count
You can also check ISO 7218
I don't think you need to reference a paper for this. CFUs are colony forming units per unit volume (ml or ul). This is a number easily calculated by plating out several dilutions, counting colonies, and calculating back to a unit of volume. The original reference, if you can find it, is likely 100+ years old.
As Gregory already pointed out, the formula you mention is quite standard knowledge/practice in any microbiology lab, a reference is not really needed. If you want to point to an additional source on the topic I would probably suggest the following book:
- Laboratory Exercises in Microbiology, 10th Edition (2017) by J.P. Harley,
Published by McGraw-Hill (ISBN: 978-0072556803)
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