What is antibiotic resistance?

In medicine, bacteria and other germs are said to be resistant if they are especially able to withstand exposure to external influences. An example: Most germs that enter the stomach with food will be killed by stomach (gastric) acid. But some bacteria are covered with a mucous coating that protects them from the acid. They are resistant to gastric acid.

Resistance to antibiotics works on a similar principle: The bacteria have acquired a new property that protects them from the antibiotic. Some types of bacteria can produce a substance that makes certain antibiotics ineffective, for example. Bacteria that can protect themselves from several different antibiotics are referred to as “multiresistant.”

What causes resistance?

Many of the bacteria that are now resistant used to be sensitive to antibiotics. The drugs were able to render certain types of bacteria harmless and therefore effectively stop infections. The medications could originally “disarm” certain types of bacteria and then effectively stop the infection. Over time and through random influences, however, the genetic material of bacteria can change. But the genetic material of bacteria can change by chance over time, sometimes creating new properties that can make the bacteria resistant to the antibiotics. These kinds of properties can also be transferred from one type of bacteria to another.

If antibiotics are used very often, resistant bacteria are better able to reproduce because the other non-resistant strains of bacteria are stopped and only the resistant bacteria remain. This leaves more space and nutrients to allow them to continue to multiply. Antibiotics then no longer help against infections caused by resistant bacteria.

Which bacteria are resistant and why are they dangerous?

Strains of Streptococcus and Staphylococcus bacteria are often resistant to antibiotics. One example is called “methicillin-resistant Staphylococcus aureus” (MRSA). Staphylococci can be found on skin and mucous membranes and may cause infection – for example if they get into open wounds.

Resistant strains have now developed in other types of bacteria, such as Escherichia coli, Klebsiella and pseudomonads.

What is being done about antibiotic resistance?

In Germany, antibiotics are prescription-only. This means that doctors are first and foremost responsible for careful and appropriate use. They should first see whether someone actually has a bacterial infection. If they do, then it's important that the antibiotic is prescribed at the right dose and for long enough, and that the right antibiotic is selected that will most effectively fight the bacteria.

There are also hygiene regulations to keep resistant bacteria from spreading further and preventable infections from occurring. These measures are especially important in hospitals. Antibiotics are used there quite frequently, so resistant germs can quickly develop. To protect yourself from these germs and prevent them from spreading, you can wear disposable gloves, a medical mask that covers your nose and mouth, and a gown. Using hand sanitizers also helps. This is especially true if you have contact with a person who is infected with resistant bacteria. This is especially important if you come into contact with someone who is infected with resistant bacteria.

Vets and farmers use antibiotics too. So vets also have to comply with the rules for handling antibiotics sensibly.

What can you do to prevent antibiotic resistance?

Being cautious about taking antibiotics can help prevent both antibiotic resistance and side effects.

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Do not overestimate what antibiotics can do: Patients often expect to be prescribed antibiotics even though antibiotics won't help to treat their medical problem.

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 caused by viruses, such as a cold or influenza (“the flu”). Antibiotics will usually be of no help here because they only fight bacteria. Antibiotics can also have side effects such as allergic reactions, stomach and bowel problems, nausea and fungal infections.

What's important to consider when taking antibiotics?

Antibiotics should be taken for as long as the doctor has prescribed them. Just because the symptoms of the illness go away, it doesn't mean that all of the germs have been killed. Remaining bacteria may cause the illness to start up again. So you should ask your doctor instead of simply stopping the treatment on your own.

If there are some tablets left over, they should not be kept for later use or given to other people. Leftover medication can be disposed of in the normal garbage or dropped off at some pharmacies. Pharmacies are not obligated to accept opened medicine though. It is important not to dispose of the medication by pouring it down the drain or flushing it down the toilet. That is bad for the environment and also contributes to bacterial resistance.

Medications can only work properly if they are used correctly. It is important to know the following things when taking antibiotics:

• Can the tablets be broken into smaller pieces to make them easier to swallow? That depends on the specific medication. Doing this might stop some antibiotics from working properly.
• What food can you take antibiotics with? Antibiotics are usually taken with water because taking them together with fruit juices, dairy products or alcohol can affect how the body absorbs some drugs. Dairy products include milk as well as butter, yogurt, and cheese. After taking an antibiotic you may need to wait for up to three hours before eating or drinking any dairy products. Grapefruit juice and dietary supplements containing minerals like calcium may also lessen the effect of antibiotics.
• When should you take antibiotics? Some antibiotics are always meant to be taken at the same time of day, others are meant to be taken before, with or after a meal. If you are supposed to take the medicine three times a day, for example, it usually needs to be taken at set times so that the effect is spread out evenly over the course of the day. An antibiotic that needs to be taken every 8 hours could be taken at 6 a.m., 2 p.m. and 10 p.m.
• Can you take antibiotics together with other medications? Because antibiotics can interact with other medications, it's important to tell your doctor if you take other medications too. Antibiotics might interact with some blood thinners and antacids (heartburn medicine), for example. Some antibiotics can make birth control pills less effective.

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The package insert contains detailed information on the use of the antibiotic. You can ask your doctor or pharmacist if you are unsure what else to watch for when taking it.

Sources

• Bundesministerium für Gesundheit (BMG), Bundesministerium für Ernährung und Landwirtschaft (BMEL), Bundesministerium für Bildung und Forschung (BMBF). DART 2020. Abschlussbericht. 2022.
• Centers for Disease Control and Prevention (CDC). About Antimicrobial Resistance. 2025.
• Deutsche Gesellschaft für Infektiologie (DGI). S3-Leitlinie Strategien zur Sicherung rationaler Antibiotika-Anwendung im Krankenhaus (in Überarbeitung). AWMF-Registernr.: 092-001. 2019.
• Kayser FH, Böttger EC, Deplazes P et al. Taschenlehrbuch Medizinische Mikrobiologie. Stuttgart: Thieme; 2022.
• World Health Organization (WHO). Antimicrobial resistance. 2023.

• IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

  Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

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