There are many disinfectants advertised in stores and in the media that report killing 99.9% of bacteria. Although this presents as extremely effective, it’s actually not. Optimized effectiveness requires a bacteria kill rate of 99.999%, or better, by the disinfectant.
Why be so fussy about the difference between kill rates?
It comes down to the risk of infection. Bacteria are microscopic, single celled organisms. Some bacteria can cause infection with less than 100 cells. Susceptible individuals (e.g., the very young, the immunocompromised, and the elderly) are especially at risk from an opportunistic infection. Whenever the risk of infection is high, it’s even more important to reduce the number of harmful bacteria to the lowest number possible.
Why 99.999% or Better Kill Rates for True Effectiveness?
Let’s look at a specific example . . . Imagine a surface contaminated with raw poultry that has 1 million bacteria per square centimeter. A disinfectant that only kills 99.9% of bacteria would still have 1000 bacteria remaining. One that kills 99.999% would have 10 remaining, and one that kills 99.99999% would have 0.1 remaining (viz., 1 bacteria in 10 square centimeters). The number of bacteria can double in a very short time. In particular, E.coli can double every 15 minutes in ideal conditions. Therefore, 1000 E. coli bacteria become 2000 after 15 minutes, 16000 in 1 hour, and 4 million in 3 hours (viz., a 4000-fold increase within 3 hours!). Now know this . . . If a disinfectant that kills 99.99999% of bacteria were used, only 400 bacteria would appear within the same 3 hour period (viz., a truly effective 10,000-fold decrease!).
Which disinfectant would you rather use
when your personal health and that of your family's
is at stake?