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This content is taken from the Uppsala University's online course, Antibiotic Resistance: the Silent Tsunami. Join the course to learn more.

Skip to 0 minutes and 7 seconds Before we go into details on antibiotic resistance, it’s important to realise that this is a natural phenomenon. It’s a bacterial evolution. Bacteria were the first living organisms on this planet. And they have evolved over millions of years in order to survive. Antibiotics and similar molecules have been present in their close environment, produced by other microorganisms to protect them against bacteria. And then the bacteria were forced to develop resistance. In fact, many of the resistance genes we’re struggling with today have been shown to originate from harmless bacteria in the environment and have then been transferred to pathogenic bacteria that cause clinical infections.

Skip to 0 minutes and 55 seconds This process has been accelerated during the past decades, of course, as a result of the massive antibiotic use in humans and animals. Bacteria are all around us in the environment. Also, there are billions of bacteria inside and on the human body, referred to as the normal flora. In fact, if you would put them together, they would weigh approximately two kilos. The bacteria help us by degrading the food we eat. They protect us against other invading pathogens. And they probably have a lot of other functions as well that we are just beginning to understand. For example, there seems to be a correlation between a disturbed intestinal flora and the risk of having a chronic disease, such as allergy or diabetes.

Skip to 1 minute and 50 seconds The normal flora is surprisingly stable over time, probably for a very good reason. Still sometimes, our friendly bacteria will cause clinical infections. For example, E. coli, which is part of our intestinal flora, is the predominant cause of urinary tract infections. And wound infections are typically caused by staph aureus or streptococci, which are part of our skin flora.

Skip to 2 minutes and 20 seconds There is a continuous exchange of bacteria between people in the community and in particular, between family members. This transfer will in most cases be silent and result only in a symptomatic carriage of that bacteria. And importantly, that goes also for multidrug-resistant superbugs. But sometimes, of course, it will result in a clinical infection.

Skip to 2 minutes and 49 seconds To summarise, bacteria outnumber humans by far. They have existed and evolved during millions of years, and they will continue to do so. So whatever new antibiotic we come up with, there is a high risk that resistance to that drug exists already somewhere in the environment and will be transferred to pathogenic bacteria.

Skip to 3 minutes and 13 seconds We depend on bacteria for our well-being, and therefore, the aim of antibiotic therapy is not to eradicate bacteria completely. It is to kill the few bacteria that cause a clinical infection right now, while at the same time saving as much as possible of our normal flora and to keep antibiotic exposure in total as low as possible to delay emergence of resistance. This week, you will learn more about antibiotic use, resistance mechanisms, and common bacterial pathogens. So please have a look at the following sections, including tables and factsheets and other materials. Thank you.

Bacterial evolution and importance of normal flora

Before we go into details about antibiotics and resistance, watch Thomas give a brief introduction about bacterial evolution and their importance for the normal flora.

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This video is from the free online course:

Antibiotic Resistance: the Silent Tsunami

Uppsala University