Do all pathogens require the same UV dose for log reduction?
No. The UV Dose requirements to achieve a certain log reduction are different for all pathogens. For example as you can see in the video above, to achieve a 4 log reduction for E. Coli you would need a UV dose of 12.8 mJ/cm 2 whereas for Salmonella you would need a UV dose of 7 mJ/cm 2.
Does UV light kill more bacteria than 4-logs?
So, a UV light that manages to get a 2-log kill leaves 100 times more bacteria to breed and infect the next patient than does a process that gets a 4-log kill. One hundred times more pathogens as a penalty for just a 2-log difference in killing ability!
Can UV light kill C diff spores?
So, a UV light that manages somehow to get a 2-log kill on an array of one million C. diff spores spread around a room will leave 10,000 of them on surfaces, each fully capable of causing the next patient in that room to develop a devastating and potentially fatal infection.
Do low log disinfection solutions leave pathogens behind?
Low log disinfection solutions can leave dangerous pathogens like C. diff, C. auris, and norovirus behind.
What is log reduction?
Log reduction is a mathematical term that is used to express the relative number of living microbes that are eliminated by disinfection. For example, a 1 log reduction corresponds to inactivating 90 percent of a target microbe with the microbe count being reduced by a factor of 10.
What is the UV response?
UV Dose Response: Every pathogen, based on its biological make-up, has a unique spectral sensitivity “fingerprint.”. Depending on the UVC wavelength range being used, each microbe will require a different amount of energy to be inactivated.
Regulatory Definitions
Disinfection, decontamination and sterilization have specific definitions that are determined by the EPA and have public health/safety implications. These definitions are relied on by infection preventionists, nurses, environmental services and more to ensure their protocols meet federal regulations.
UV and Clostridioides difficile (C. diff)
Studies show that UV light treatment may only achieve a 1 to 3 log reduction in organisms like C. diff. 18 This results in a significant amount of untreated colony forming units (cfu).
How many logs does sterilization kill?
Sterilization means a kill of at least 6+ Log
What is a 6.0 log?
Hospital surfaces can be contaminated with pathogenic organisms (bio-burden), and only achieving a Log Reduction below 6.0 Log means dangerous viruses, bacteria, fungus, and Clostridium difficile (C-diff) spores, can or will be left behind to proliferate and repopulate surfaces within the treated area. The literature has shown that bio-burden can be spread around to contaminate patients and/or grow new bacterial and fungal colonies on new surfaces. (1)
How many C diff spores can UV light kill?
So, a UV light that manages somehow to get a 2-log kill on an array of one million C. diff spores spread around a room will leave 10,000 of them on surfaces, each fully capable of causing the next patient in that room to develop a devastating and potentially fatal infection.
How does a 6 log kill work?
A 6-log kill reduces the colony to 1 MRSA bacterium after a 99.9999% reduction. So, a UV light that manages to get a 2-log kill leaves 100 times more bacteria to breed and infect the next patient than does a process that gets a 4-log kill.
What is the scale used to measure the number of bacteria in a disinfectant?
Scientists use a logarithmic scale. Log reduction stands for a 10-fold (or one decimal point) reduction in bacteria, meaning the disinfectant reduces the number of live bacteria by 90 percent for every step.