Why can't we see bacteria

Bacteria are everywhere Where do most germs lurk?

SEND DATEThu, 1.6.2017 | 10:00 pm | SWR television

Bacteria were discovered 300 years ago. But to this day we only know one thing for sure about them: they are everywhere. Odysso tests: when and where do we have potentially harmful contact with them?

We come into contact with bacteria through our hands and also distribute them further. But where are which bacteria actually lurking in our everyday lives? We do a test; our test subject is Louisa. For one morning we will accompany her through her everyday life and examine which bacteria she comes into contact with during this time and how many actually stick to her hands.

In the bathroom

We take the first so-called set-off test from her hands as soon as we get up. The red culture medium of the contact plates consists of blood agar; it contains sheep's blood. Professor Reinier Mutters from the Institute for Medical Microbiology and Hospital Hygiene at the University of Marburg evaluates the samples for us. What did the test show after getting up and washing your hands? The expert says there are around 50 germs on a clean, washed hand. "Louisa had significantly more germs on her hand, namely 300. That may be because she didn't wash her hands properly or the towel she used to dry herself with wasn't clean. That can happen." Especially with the towel, you should make sure to change it regularly.

In the kitchen

Which bacteria are still on Louisa's hands in the course of the day? To find out, there is now a strict hand washing ban! The first candidates are already lurking in the kitchen - for example in the sponge. And it has been in use for a relatively long time - around four to five weeks. This is not such a good idea, our contact test shows. Intestinal and skin bacteria, but also faecal germs, live in the sponge. They mostly come from food and in the worst case scenario can lead to pneumonia or blood poisoning.

In the tram

The bacteria are probably now sticking to Louisa's fingers and that has consequences: Because where there are many people, the exchange of bacteria usually works particularly well. For example on the way to work, in the tram. Louisa also collects other bacteria here. According to the expert, metal rods and holding buttons are harmless, as no bacteria can multiply on metal, but our contact test showed relatively high numbers of germs on the seat - again germs that occur naturally on the skin, but also germs that do not belong there, like Acinetobacter, which can cause infection if transmitted in large quantities.

In the supermarket

Many people suspect large amounts of bacteria on the handrail of an escalator. But that's not true: The germ load of the escalator is rather low and harmless. The situation is different with the handles of shopping trolleys. Very often classic "human germs" abound here on the handle, such as harmless skin germs - but also diarrhea pathogens that cause illness. The handles are a hygiene weak point because they are usually not cleaned that often.

In the office

Bacteria have also spread to Louisa's workplace. The door handle alone is colonized with a good 400 germs. Even more disgusting: telephone and computer keyboard. Both have way too many gut and fecal bacteria. These can then even continue to multiply on damp hands. And what about the busy toilets, is it getting worse now? Professor Mutters gives the all-clear for our test toilet: "The toilet is a frightening place for many people. But in our case that was not at all dramatic. That means we found higher germ counts, but no germs that should worry us. " If toilets are cleaned regularly, they are one of the places with the least colonization of germs.

Six hours without washing your hands

Louisa didn't wash her hands until lunchtime, a good six hours. How many bacteria are now on your hands? Interestingly enough, in total about as many as in the early morning. However, Professor Mutters cannot give the all-clear: "Louisa contaminated herself with some germs during her day that are not necessarily pleasant. In addition to intestinal germs, enterococci, there was also a Staphylococcus aureus, a pus germ, and an Acinetobacter. That is a germ who can cause pneumonia in the hospital and infections in a patient with weakened immune systems.


Tip for washing your hands correctly: As a rule of thumb, wash your hands for at least 20 seconds after each use of the toilet and before eating, including between your fingers. Also very important: dry your hands thoroughly so that bacteria cannot multiply.

Sabine Guth

Status: 1.6.2017, 9.00 a.m.