Saturday, May 23, 2009

Don’t read this if you have a weak stomach

The reason for the title will become apparent later on!

People who have an opportunity to influence the public have a duty to make sure they know what they are talking about and to think about the consequences of their comments.

Last week, popular TVNZ breakfast show host Paul Henry was talking about the state of cleanliness in public toilets. The breakfast show is a mixture of news, views and entertainment and Paul made a meal (if you’ll pardon the pun) of the issue, drawing out as much toilet humour as possible. Unfortunately, he also claimed that washing your hands in a public convenience would result in your hands being more contaminated than if you had not bothered.

This is hard to stomach. Certainly, taps and door handles may be contaminated, often with faecal bacteria and it may be that soap and soap dispensers are also contaminated. However, I find it difficult to accept that not washing hands is better than washing.

If you didn’t take the earlier warning, now is the time to quit reading.

If you have wiped your backside with toilet tissue, then the chances are that your fingers are contaminated with faecal bacteria and viruses. Way back when I started teaching food microbiology, I used to run an exercise with my students. They took various numbers of sheets of toilet tissue and placed them over a finger end, which they then gently wiped across a Petri dish of indicator bacteria. These, as it happens, were Escherichia coli, the bacteria always present in the gut. These bacteria have the ability to produce a green metallic sheen when they grow on an agar called Eosine Methylene Blue. Since they occur only in the gut, we should not normally expect to find them on our hands, except for the obvious reason. After the wiping phase of the experiment, the tissue was discarded and the same finger pressed onto the EMB agar, which was then incubated overnight. The students then washed their hands and dried them before making a further agar impression.

The students were usually horrified to discover that even when using 6 sheets of 2-ply toilet tissue, their finger impressions often grew bacterial colonies with a green metallic sheen. Now, not to put too fine a point on it, 6 sheets is an almost unmanageable wad of paper! Washing usually removed all the bacteria, but only if soap and warm water were used.

There are several messages here.
• No matter how much tissue you use, you can’t be sure that you won’t have faecal bacteria and viruses on your fingers.
• Washing your hands with soap and then drying them will remove most of the bacteria

Unfortunately, when you turn on the tap with contaminated hands, they will transfer bacteria and viruses to the tap. After you have washed, you recontaminate your hands when you turn the tap off. That’s why in hospitals and laboratories the taps have long handles that can be operated with wrists or forearms, or are operated by foot pedals or infra-red sensors. These days, many washroom taps have press buttons that allow the water to run for only 30 seconds or so and don’t need to be turned off.

So what can you do?
• Turn the tap on with your wrist
• Wash your hands thoroughly with soap (sing “Happy birthday" to yourself twice to ensure you wash for long enough)
• Thoroughly dry your hands on a paper towel and then use it to turn the tap off
• If the washroom has blower hand dryers, be careful not to touch the machine (if it has an on button, push it with your knuckle)

Watch a microbiologist in a washroom. When I go in there, I do all the above and then open the door with the crook of my little finger. It’s not foolproof, but a lot better than not washing. If you are still paranoid, buy a small spray bottle of hand sanitizer and carry it in your bag for use after you have left the washroom and before you eat.

I hope you read this far, Paul.

3 comments:

mountainbikingzane said...

I remember being student of yours John, and doing the toilet tissue/e. coli/hand washing experiment. It certainly made sure that your students were well aware that they should be washing their hands!

Corey said...

I was shocked at how many people believe they should not wash their hands in public places believing that the faucet is more contaminated than their poopy fingers. It shows how big the gap has become between the public's perception of health risk vs. the real risk.

Yakout Esmat said...

How come we don't see any of the toilet seats that are in use all over Japan and many other Asian countries where a built-in water jet sprays water (could be warm water) cleaning our .....without having to use tissue papers or touch you know what?. This is called a good use of modern civilisation..

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