Fact Check: Are Hospitals the Only Source of Multidrug-Resistant Bacteria?

As the German news channel NTV and BR Wissen stated, multidrug-resistant bacteria are often called superbugs or hospital germs^1,2. Those are bacteria, that can withstand the treatment with antibiotics, often even multiple antibiotics, and are therefore hard to get rid of. Annually infections with multidrug-resistant bacteria cause more deaths than HIV or malaria³.

Despite the indication of the name “hospital germ”, several environments and reasons exist that enable the evolution of multidrug-resistant bacteria. The evolution of multidrug-resistant bacteria is linked to the presence and easy spread of bacteria in general, as well as the heavy application of antibiotics. In the following we examined why not only hospitals, but also agriculture and the food sector play a detrimental role in the formation and spreading.
Antibiotics can promote the emergence of multidrug-resistant bacterial strains, since the selective pressure favours the survival of randomly resistant individual bacteria^4,5 . Because bacteria pass on the resistance to their offspring, it is very likely that new resistant bacteria strains will evolve.     
Bacteria spread easily in hospitals. First, they have many opportunities to enter the bodies of people, so called potential infection routes, due to the increasing variety of medical procedures and invasive techniques. Bacteria can also reach susceptible hosts via contact with staff or visitors. Bacteria that enter the bodies of patients can often not be combated by the body, since the patients´ immune system is often strained with previous diseases and treatments. Patients often receive antibiotics for therapy or prophylaxis. Along with the presence of bacteria and susceptible hosts, the high amount of antibiotics are the last puzzle piece for the evolution of multidrug-resistant bacteria^4,5 .
Now that multidrug-resistant bacteria had an opportunity to evolve, they have the chance to disseminate easily via human contact and medical procedures. Especially shared hospital units with multiple beds and lacking hygiene standards provide ideal conditions for the spread of multidrug-resistant bacteria in hospitals⁶. Despite the progress in health and hospital care, infections with multi-resistant bacteria continue to develop in hospitalized patients⁷.
As examined, many multi-resistant bacteria can come from hospitals. However, antibiotics are also used excessively in the livestock sector. Here, antibiotics are used to control infections and improve animal growth and productivity. Because of the amount of closely kept susceptible hosts, intensive mass animal farming is an ideal ground for formation and spread of resistant bacteria^8,9,10,11. Those bacteria are transmitted to humans by eating contaminated foods^12,13,14. Multidrug-resistant bacteria were found in both meat and fresh produce¹⁵. Even though multidrug-resistant bacteria can evolve in just one infected organism, travelers can unknowingly carry such resistant strains, making this a global problem in a globalized world¹⁶.

To summarize, multidrug-resistant bacteria do not exclusively originate in hospitals. In hospitals as well as in the livestock sector the key factor causing the formation of those hard-to-treat bacteria is the heavy use of antibiotics.

Issue 5
Sabine Zantop Linares, Nina Bürger, Judy Menz, Charlice Hill