Fast-food giant McDonald's has been rolling out touchscreen self-order kiosks in its restaurants for the past several years. While they make ordering your Big Mac, fries, and chocolate shake more efficient and accurate (and they're actually kind of fun), yesterday scientists revealed that they found something on those touchscreens that should be of tremendous concern for McDonald's customers.

Bacteria.

But not just any kind of bacteria -- fecal and other bacteria from human digestive tracts that could cause all sorts of health problems for someone who happens to ingest the living organisms.

According to Dr. Paul Matewele, a senior lecturer in microbiology at London Metropolitan University:

We were all surprised how much gut and fecal bacteria there was on the touchscreen machines. These cause the kind of infections that people pick up in hospitals. For instance Enterococcus faecalis is part of the flora of gastrointestinal tracts of healthy humans and other mammals. It is notorious in hospitals for causing hospital acquired infections.

In addition to fecal bacteria, the scientists also found staphylococcus, listeria, klebsiella, and proteus bacteria, all of which can cause illness in humans.

The samples were gathered by the U.K. newspaper Metro from eight different McDonald's restaurants in England -- six in London and two in Birmingham -- and then analyzed by Dr. Matewele and his team. Shockingly, touchscreens in every one of the restaurants had bacteria, often virulent, living on them. 

And as touchscreens become a greater presence in our lives, the problem is likely to get even worse. Says Dr. Matewele:

Touchscreen technology is being used more and more in our daily lives but these results show people should not eat food straight after touching them, they are unhygienic and can spread disease. Someone can be very careful about their own hygiene throughout the day but it could all be undone by using a touchscreen machine once.

According to a McDonald's statement, the company is careful to routinely clean the touchscreens to avoid problems such as those revealed by Dr. Matewele:

Our self-order screens are cleaned frequently throughout the day. All of our restaurants also provide facilities for customers to wash their hands before eating.

If you're not loving the idea of coming in contact with one or more of the listed bacteria, then consider bypassing the kiosks altogether and ordering the old-fashioned way -- at the register with a real, live person.