What is antibiotic resistance?

Bacteria are found all through our bodies as part of our normal so-called flora. They also constantly enter our bodies from the outside. Bacteria are not all harmful. On the contrary: many bacteria play an important role in metabolic processes and the immune system.

In medicine, bacteria and other germs are said to be “resistant” if they are particularly good at resisting influences that are harmful to them, such as treatment.

Harmful bacteria can be fought by the body’s own immune system or with medication. Antibiotics are often very effective in the treatment of bacterial infections. But sometimes, for various reasons, neither the body’s immune system nor antibiotics are able to successfully fight bacteria. This may be, for example, because the bacteria have changed and become “resistant” to certain drugs, ensuring that they survive.

How does drug resistance develop and what contributes to growing resistance?

Antibiotic-resistance emerges in bacteria as a result of natural adaptations, spontaneous changes in DNA (mutations), or when different bacteria exchange genes with each other. Bacteria become resistant if they “take” resistance-inducing genes from other bacteria and use them as a protective shield against medication. If the bacteria are resistant to several antibiotics at the same time, they are called multiresistant bacteria. Multiresistant bacteria are found in hospitals because there are a lot of different germs in hospitals and a lot of different antibiotics are used there. That is why good hygiene in hospitals is also critical to prevent bacteria from becoming resistant.

Other factors that play an important role in the development and spread of resistant bacteria include:

• overuse of antibiotics,
• not taking them long enough or regularly enough and 
• the widespread use of antibiotics in farm animals.

Antibiotics are commonly prescribed to treat medical conditions for which they are not suitable. For example, they are often used to treat common colds, which are usually caused by viruses. But antibiotics can only fight bacteria. On top of that, so-called broad-spectrum antibiotics are also used too often. Broad-spectrum antibiotics fight many different types of bacteria. Using them a lot increases the likelihood of a wide variety of different bacteria becoming resistant. In some cases narrow-spectrum antibiotics, which specifically target a certain type of bacteria, would work just as well.

To find out exactly what kind of bacteria is causing an infection, samples of urine or saliva, for example, can be taken and analyzed in a laboratory. However, it can take several days before the test results come back.

Some people do not take antibiotics regularly or long enough, so too many of the harmful bacteria may survive. This increases the risk of getting ill again because the bacteria are still there. The bacteria that are left over can adapt and become resistant, which means that even more antibiotics are needed to kill them.

Which bacteria are resistant to antibiotics and why are they dangerous?

Bacteria that are often resistant to antibiotics include strains in groups called “streptococcus” and “staphylococcus” bacteria. One example is called “methicillin-resistant Staphylococcus aureus” (MRSA). Staphylococcus bacteria are found on skin and mucous membranes, and can cause harm if they multiply too much.

If bacteria become resistant, it not only means that many antibiotics will not work: the bacteria can also no longer be prevented from spreading. Infections caused by such bacteria can take a long time to clear up, or may even never go away. This can have serious consequences, particularly for young children and people with weak immune systems, such as older and chronically ill people. 

What is important to consider when taking antibiotics?

If you have an infection and your doctor has not prescribed antibiotics, it is important to understand why not. The key question is whether or not you need antibiotics to get better.

Antibiotics are needed to treat serious bacterial infections like lung infections or meningitis (inflammation of the membranes lining the brain and spinal cord). This is not the case when, for example, people who are otherwise healthy have respiratory infections such as a cold or influenza (“the flu”): antibiotics are used too often to treat these illnesses although they do not help much. You can find out more about antibiotics and common colds here, and about antibiotics for middle ear infections here.

Antibiotics can often lead to adverse effects like allergic reactions, stomach and bowel problems, nausea and fungal infections, so it is important to talk to your doctor about the possible pros and cons before taking them.

If you take antibiotics, it is important to take the right dose regularly and long enough. You can find out how to use antibiotics properly by asking your doctor, pharmacist or reading the package insert. Depending on the medical condition, antibiotics usually have to be taken for several days or sometimes even weeks before the infection clears up.

Generally speaking, there should be no tablets left in the package when you have finished your treatment. One package usually contains the right amount for one course of antibiotics. If there are some tablets left over, they should not be kept for later use or given to other people. It is best to take leftover medication to a pharmacy. Throwing it into a bin or the toilet is bad for the environment and can also contribute to the development of antibiotic resistance.

The correct and safe use of medication

It is important to follow instructions for use when taking any medication, because the way you take it can influence how well it works. You can find out how best to take various medications by asking your doctor or pharmacist, or by reading the package insert.

For instance, it may be easier to take certain tablets by breaking them into smaller pieces or crushing them. But sometimes doing this could stop the medication from working properly. It is also advisable to take medication with water only, because juices, milk or alcohol could influence the way that some drugs are absorbed into the bloodstream.

The time of day when you take the medication is important, too: Should it be taken before or after meals? Should you wait a certain amount of time before taking the next dose? For example, if a medication should be taken three times a day, it can be taken at fixed times (in the morning, at lunch, in the evening). There should be a certain time interval between doses so that the amount of the medication in your body stays as steady as possible.

If you are already taking medication regularly, it is important to be aware of potential interactions between that medication and the medication you are considering using. You can read more information about taking medication here.

Author: German Institute for Quality and Efficiency in Health Care (IQWiG)

References

• IQWiG health information is based on research in the international literature. We identify the most scientifically reliable knowledge currently available, particularly so-called “systematic reviews”. These summarize and analyze the results of scientific research on the benefits and harms of treatments and other health care interventions. You can read more about systematic reviews and why these can provide the most trustworthy evidence about the state of knowledge here. The authors of the major systematic reviews on which our information is based are always approached to help us ensure the medical and scientific accuracy of our products.
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