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Antibiotic resistant bacteria

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Antibiotic resistant bacteria

Invisible to the naked eye and occurring in vast numbers almost everywhere you look, disease-spreading bacteria are a frightening prospect! But what makes them even more alarming is their innate ability to overcome the medicines we use to prevent bacterial infections. This phenomenon is called antibiotic resistance. Antibiotic resistance within bacteria arises from the increased exposure of microorganisms to antibiotics and these microorganisms’ naturally occurring resistance response. This antibiotic resistance in bacteria is prevalent in modern society because of the exponential increase in antimicrobial medicine usage over the last few decades.

Meaning of Antibiotic Resistant Bacteria

Bacteria are single-celled organisms which are found everywhere you look! They thrive in warm, moist, nutritious conditions but can be found even in the most extreme temperature and pressure environments on earth. Some bacteria are beneficial (such as bacteria in your gut which help digestion), but certain bacterial microorganisms will cause disease, and some are even fatal. To counteract these disease-spreading organisms, scientists have developed antibiotics, which are antimicrobial drugs that help kill exclusively bacterial cells in our body without targeting our own cells! Despite the best efforts of antibiotics, clever bacteria often overcome the advances of these drugs by mutating and developing drug resistance mechanisms, continuing to cause disease! This is a natural process, as selection pressures favour bacteria with resistance genes.

Antimicrobials or antibiotics are drugs which halt the growth of microbes like bacteria often by disrupting their cell wall. A Resistance gene is a gene which provides the microbe with the tools to resist the effects of an antimicrobial drug. This gene could arise from a mutation in the bacteria’s DNA or even be transferred from another bacteria!

Check out the Bacterial Diseases article to learn some examples of diseases caused by Bacteria!

Evolution of antibiotic resistance in bacteria

Cumulative mutations in a species’ genome provide crucial genetic variation in a population and enable species to survive under selective evolutionary pressures. This is no different in bacteria! These microbes are constantly battling to survive against the antibiotics we take to kill them. Mutations in the gene sequence of bacteria can lead to them displaying different characteristics, some of which may be beneficial in defending against the effects of antibiotics. The fact that bacteria multiply at a rapid rate means that mutations within populations can quickly spread. Essentially, they can evolve much faster than other more complex organisms, like humans!

A mutation is an altering of a gene’s sequence resulting from a change of a single or multiple base unit nucleotides in the DNA, including the insertion, deletion or substitution of the base along the chromosome.

This is the process by which bacteria become resistant to antibiotics:

  1. An antibiotic is introduced to the body after the person has become infected by a specific bacteria.

  2. The population of bacteria is constantly growing, and random mutations within the population are continually occurring.

  3. Some of these mutations may cause the bacteria to exhibit characteristics beneficial in resisting antibiotic effects.

  4. These bacteria which contain the beneficial mutant gene will survive within the population, and because of bacteria’s ability to reproduce rapidly, they will become more prevalent in the population.

  5. The antibiotic kills off the bacteria without the mutant gene, so there is less competition for the bacteria with the mutant gene.

  6. The bacteria containing the mutant gene are now dominant within the population, so the antibiotic has little to no effect on the growth of the population. Therefore the ill person does not recover.

These new antibiotic resistant strains can be an issue because the prescribed antibiotic for the original bacteria will no longer work, so the disease will more easily spread. This means that pharmaceutical companies will have to find and produce new drugs which counteract the new strains of bacteria, which comes at a cost and takes time. This is a natural process amongst all bacteria but is becoming a serious public health crisis because of antibiotic overuse and misuse, which creates a selective pressure for spreading superbugs! These microbes are much more difficult to kill!

Superbugs are microbes which are resistant to multiple antimicrobials. MRSA is considered a superbug, as it can withstand the effects of various antibiotics such as methicillin, penicillin and amoxicillin. MRSA is especially present in hospitals, where it spreads through person-to-person contact.

Bacteria and natural selection

The development of antibiotic resistant strains in bacteria is a comprehensive source of evidence for Darwin’s theory of evolution, as it displays natural selection. This natural selection is exhibited by the ‘fitter’ population of bacteria surviving and reproducing when the antibiotic is present, whereas the less ‘fit’ population of bacteria without the resistant strain will decrease in the presence of the antibiotic.

Natural selection is the process by which organisms displaying characteristics that are beneficial in their environment can survive and pass on their genes more often. These characteristics then become more prevalent in the population. These phenotypes arise from genetic mutations between generations.

Check out the Theory of Evolution article to learn more about natural selection!

Examples of Antibiotic Resistant Bacteria - Types of Bacterial Infections

Here are some examples of antibiotic-resistant bacteria prevalent in human populations that you should know.

Cloistriodioides difficile

  • Infection: Spreads through hand-to-hand contact and lives on surfaces. Ingestion of bacteria leads to infection of the large intestine.
  • Resistance: Just under half of all prescribed antibiotics have little to no effect on the clostridioides bacterium.

Methicillin-resistant Staphylococcus aureus

  • Infection: MRSA bacteria are usually spread by skin-on-skin contact with someone infected or who has the bacteria on their skin. MRSA can cause fevers, headaches, breathing difficulties and muscle pain.
  • Resistance: MRSA spreads easily in hospitals, which has led to the bacteria becoming resistant to a range of antibiotics such as methicillin, penicillin and amoxicillin.

Drug-resistant Neisseria gonorrhoea

  • Infection: Gonorrhoea is a sexually transmitted disease and causes frequent urination, pus-like discharge from the penis, redness of the penis and a sore throat in males. Females experience pain during urination, fevers, pain during sexual intercourse and shooting pains in the lower abdomen.
  • Resistance: Gonorrhoea is such a widespread disease globally that it has developed resistance to many antibiotics used for its treatment. These include penicillin, macrolides and tetracyclines.

Multidrug-resistant mycobacterium tuberculosis

  • Infection: Early infection, namely ‘latent TB’, has no symptoms as the immune system protects against the bacteria. Active TB, however, can cause coughs, fevers and loss of appetite.
  • Resistance: MDR-TB is resistant to so many antimicrobials that the patient must be treated with up to 5 different drugs.

Preventing antibiotic resistance

Since the discovery of antibiotics and their subsequent development, deaths caused by bacterial infections have plummeted. Unfortunately, this increased use of antibiotics has led to the rise of resistant bacteria, primarily because of the over-prescription of antibiotics. This occurs as the presence of antibiotics allows the resistant bacteria to have a survival advantage over the non-resistant bacteria. Here are some ways that increasing antibiotic-resistant bacteria can be prevented:

  • Doctors should only prescribe antibiotics to their patients when they are indispensable.

  • Completing the entire course of antibiotics is essential to make sure all bacteria are wiped out and so there is no chance of the remaining bacteria reproducing to form a resistant population.

  • Bacteria must be treated with their specific antibiotic, and the use of antibiotics which work for many bacteria must be reduced.

  • High levels of hygiene in hospitals are pivotal in minimising infection.

Increasing antibiotic resistance in bacterial populations from the overuse of antibiotics is a huge cause for concern, so many pharmaceutical production companies are developing new antibiotics which are effective against these new strains. Despite this, the rate of development of new drugs is slow and is unlikely to match the urgency required to handle increasingly resistant bacterial strains, so it is important to prevent further increase in antibiotic resistance by putting the points above into practice.

Antibiotic resistant bacteria in agriculture

Antibiotic use is prominent in farming as they are helpful in allowing animals to grow faster and preventing them from catching diseases. Similarly to treating humans, overuse of antibiotics in agriculture has led to the increase in antibiotic-resistant microbe populations. Dangerously, these resistant strains can be passed on to humans through workers on the farm or even through meat production. This threat has led to many countries worldwide passing laws that restrict the use of antibiotics in agriculture.

Antibiotic Resistant Bacteria - Key takeaways

  • Bacteria are microorganisms which live all around us; some bacteria spread diseases that can be dangerous to humans.
  • Antibiotics are drugs which target and kill bacterial cells in the body.
  • Bacteria will develop antibiotic resistance via the natural selection of bacterial populations possessing resistant genes.
  • Doctors can limit antibiotic resistance in bacteria populations by ensuring patients complete the entire course of antibiotics and are treated with specific antibiotics for their disease.

Frequently Asked Questions about Antibiotic resistant bacteria

Antibiotic-resistant bacteria are microorganisms which possess a gene which allows them to resist the effects of antibiotics.

Random mutations in bacterial populations can lead to advantageous genes which resist the effects of antibiotics.

Random mutations in bacterial populations can lead to advantageous genes which resist the effects of antibiotics.

New antibiotics which are effective against the new strain of bacteria must be used.  Antibiotics also must not be overused.

The bacteria can break down cells and release poisonous toxins.

Final Antibiotic resistant bacteria Quiz

Question

What is an antibiotic? 

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Answer

Antibiotics are drugs that kill bacteria in the body.

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What are disease-carrying bacteria?

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Answer

Pathogens which enter the body and multiply.

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What is a resistant gene?

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A certain gene which provides the machinery for the bacteria to withstand the effects of antibiotics.

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What is a mutation?

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Answer

Mutations involve a change in the base sequence of a gene.

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What is natural selection?

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Answer

Natural selection is the favouring of 'fitter' organisms, which are those possessing advantageous genes that can be transmitted to future generations.

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Who theorised natural selection?

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Answer

Charles Darwin

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What are 'superbugs'?

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Answer

Superbugs are microorganisms which are resistant to multiple antibiotics.

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What is an example of a superbug?

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Answer

MRSA

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What is the main reason for the increase in resistant bacteria populations? 

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Answer

Overuse of antibiotics. 

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How can antibiotic resistance be prevented?

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Answer

Prescribing antibiotics only when necessary, and making sure patients complete their full course of antibiotics.

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Why is antibiotic resistance in agriculture a threat? 

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Because the resistant bacteria can be passed to humans through contact with the animals and meat production. 

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What is the difference between antibiotics and antifungals?

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Answer

Antibiotics treat bacteria, whereas antifungals treat fungi.

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How are antibiotic resistant strains dealt with?

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With new antibiotics and sensible application.

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What type of cell is MRSA?

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A bacterial cell.

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Why is antibiotic resistance proof for the theory of natural selection?

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Answer

Because the fittest members of the population survive (bacteria with the resistant gene) and reproduce.

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