Fact List YSK

5 Things You Should Know – Part 39

Here are this week’s 5 things you should know.

01. Most bacteria do not visibly ‘glow’ under UV light

UV light

A disturbing trend is the promotion of fluorescence under UV as a diagnostic tool for unsanitary areas, doubtlessly fuelled by TV crime dramas where natural fluids or organic matter are detected with UV, as well as in other TV formats in the ‘How Minging Is Your…’ genre. I’m now seeing systems being promoted in food and healthcare claiming you can expose bacteria on surfaces with UV ‘because bacteria fluoresce’. Some even suggest such systems are suitable for validation of cleaning effectiveness in food prep and healthcare.

It is true that some bacteria do glow in and of themselves and many more will glow under UV light to a greater or lesser degree, so the plausibility factor is there. And UV light is used industrially in food production and other processes to detect certain specific bacteria. As a rule bacteria do not fluoresce. Some strains of Salmonella and Shigella relevant in foodborne illness can, and many contain materials which fluoresce – but that fluorescence not always visible to the naked eye, either because it’s at the wrong wavelength or there just isn’t enough of it.

Washroom fixtures including toilets, urinals, walls, partitions, mirrors, floors and counter tops will commonly have deposits of compounds derived from urine and soap scum. When you shine ultraviolet light on surfaces with deposits of urea salts or soap scum they absorb it and emit visible light to the naked eye (if viewed in total darkness). Surfaces can be inspected with the use of an appropriate ultraviolet light but this is NOT an accurate indicator of presence of bacteria. But what it can do is indicate areas where bacteria might be found. This is where Rule 1 of hygiene and infection control comes in: You Can’t Disinfect Dirt. A surface must be visibly clean before you can disinfect it and one that fluoresces under UV most likely isn’t.

So is UV an Indicator of Bacterial Contamination?

Yes and no. There is a serious scientific flaw in the use of UV for detection of bacteria using the method described above. A recent study swabbed a number of surfaces in critical healthcare situations and looked at levels of bacterial contamination of surfaces that fluoresced under UV versus those that didn’t. It found that colony densities were significantly higher in non-fluorescing areas versus fluorescing areas. It also found that the color of fluorescence may determine the level of sanitation necessary to properly clean a room. While this is interesting one cannot ignore the fact that surfaces that do not fluoresce under UV cannot be considered either clean or free of bacterial contamination –  presence of fluorescence can indicate a surface is not clean and may well have a few good bugs on it but lack of fluorescence is not indicative of lack of bacterial contamination. It’s a great bit of science ‘theatre’ and very effective when used in hand washing etc training but (very big but) surfaces that do not fluoresce cannot be considered hygienic.

02. When you find your old vacation pictures 20 or 30 years later…

Vacation pictures

It’s the pictures of people, not buildings, that will interest you most. Your traveling companions, people on the street, the transient moments will never be repeated. So document your trip, but remember that you may enjoy your pictures much more in later years if you take more pictures of people than buildings.

Also getting pictures of family and friends enjoying a moment on vacation instead of posing for a shot will help relive moments that will bring back memories and stories that can be shared and can be much more memorable than a simple group photo or a selfie.

03. Psychological abuse called “gas-lighting”


Ever been in a situation where something has happened earlier in the day and someone you know (partner, husband, wife) denies it having happened to suit their own needs, and then turn around and call you crazy for making stuff up? This is gas-lighting and it is more common than you think. I have had people I barely know try and gas light me to try and discount arguments I am making, and/or make them feel superior. This kind of psychological manipulation is used in abusive relationships to make one party feel less sane.

04. If you have persistent heartburn


It might actually be a certain kind of bacteria. If you have had acid reflux which hasn’t responded to measures such as cutting down alcohol, avoiding aggravating foods and taking heartburn remedies then you should definitely talk to a doctor. It might be caused by a bacteria called Helicobacter (H. pylori) that can live unnoticed in our stomachs. If you haven’t had a test for this, but have frequent heartburn, then you should have a H. Pylori antigens test.

05. About 909-390-0003


909-390-0003 is an echo line that helps check your phone line’s latency (or delay). It instantly echoes back whatever it hears on its end. It’s also a good way of checking your audio quality.


Add Comment

Click here to post a comment

Your email address will not be published. Required fields are marked *


Follow Us