What are ‘Log Reductions’ and Why are they Important?
In terms of infection control, ‘Log Reductions’ convey how effective a product is at reducing pathogens. The greater the log reduction the more effective the product is at killing bacteria and other pathogens that can cause infections.
‘Log’ is short for logarithm, a mathematical term for a power to which a number can be raised. For example, if using 10 as a given number, a Log 3 increase can be shown as 103 or 10 x 10 x 10 = 1,000.
A log reduction takes the power in the opposite direction. For example, a log reduction of 1 is equivalent to a 10-fold reduction or, to put it another way, moving down one decimal place or a 90% reduction.
During product efficacy testing, the microbiology laboratories count the number of colony forming units (CFUs) of the given pathogen present at the start of the test. They then apply the disinfection product being tested, alongside a control product and wait the required test time before recounting the number of CFUs present.
The result of the difference between the control and the test product is then expressed as a Log reduction. For example, if the number of CFUs in the control was found to be 1,000,000 (or 106) and the end result using the product was only 1,000 (103), that would be a Log reduction of 3 or a reduction of 99.9%.
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Resource Person: Anas Salama Hemaid
