Antimicrobial Resistance

The information here is provided by courtesy of the Network's short online course - "An Introduction to Global Health".

Antimicrobial resistance is potentially one of the biggest threats to health that we have.

Antibiotic/antimicrobial resistance : Terms used

In the past the term "antibiotic resistance" was used to describe how bacteria started to be resistant to antibiotics. The term now used is "antimicrobial resistance".

Antibiotic Resistance : Resistance to an antibiotic is illustrated below. Image 1 is of a culture plate with a bacteria growing on the gel. The white circles are different antibiotics. The clear patches around the white circles of antibiotic are where the antibiotic has killed the bacteria.

In the plate on the left, all the antibiotics have killed the bacteria. In the plate on the right, only three have done this to any significant extent. The bacteria around the other antibiotics have not been affected as they are resistant to the antibiotics.

Image 1

(Source: Dr Graham Beards, Wikipedia https://en.wikipedia.org/wiki/Antimicrobial_resistance#/media/)

Antimicrobial Resistance : The term now in use is "antimicrobial resistance". This term covers a wider range of resistance to infections (not just from bacteria) and includes, for example, malarial parasites that have become resistant to some of the anti-malarial treatments that have been used.

Benefits and dangers of antibiotics

a) Benefits

It is difficult today to imagine what the world was like without antibiotics. There are many people alive today who would have died in their childhood had it not been for antibiotics. Before the era of antibiotics some infections like osteomyelitis could become chronic causing death of bone and months or years of purulent discharge, pain and disability.

Antibiotics have transformed our ability to manage infections. The first ones were developed in the 1930s e.g. sulphonamide. Although penicillin was discovered before this, it was first developed to be used extensively during the second world ward. Streptomycin for the treatment of TB was discovered in 1943.

b) Dangers

a) Use in humans

If an antibiotic does not kill all the organisms being treated e.g. a treatment is not finished, the dose is not high enough, then resistance to the antibiotic can develop.

Antibiotic resistance has widened over the last few decades and for some organisms there are only one or two very expensive antibiotics remaining that are effective. Resistance to antibiotics is, for example, currently found in Kebsiella peumoniae, E. coli, gonorrhoea, tuberculosis, malaria, HIV and more.

The development by Staphylococcus aureus is a good example of this (Figure 1)

Figure 1

Source : Waves of Resistance: Staphylococcus aureus in the Antibiotic Era. Henry F. Chambers and Frank R DeLeo. NCBI. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871281/

This is a growing threat that is also relevant to the success of major surgery and cancer chemotherapy when a person's immune system may be affected.

Use in animals

The use of antibiotics is widespread in animals- not for treating disease but for fattening the animals up. (Image 2)

Image 2

Source : WHO - https://www.who.int/news/item/07-11-2017-stop-using-antibiotics-in-healthy-animals-to-prevent-the-spread-of-antibiotic-resistance.

Over time the organisms become resistant to the antibiotics used in animals. The resistant organisms can then be transferred to adults with severe consequences. Restricting the use of antibiotics in food producing animals can reduce antibiotic resistance in the animals by up to 39%. (See ** in further reading below)

How antimicrobial resistance develops

When an antibiotic is given it kills the bacteria that are susceptible to it. There will usually be a few bacteria, however, that are not susceptible. (There may also be some bacteria that are partially susceptible and, if the antibiotic is not given for long enough, are able to survive). With the susceptible bacteria having been killed off, this leaves space for the resistant bacteria to multiply, so there are more of these around. Sometimes, these bacterial can pass on their resistance to other bacteria too. (Figure 2)

Figure 2

This prize winning You Tube video below provides a good description of the development of resistance to antibiotics.

https://www.youtube.com/watch?v=yHs0GyLNSLg

Drivers of antibiotic resistance

These include

Poorly managed use in humans
Widespread use in animals
Transfers between humans e.g. in hospital, between countries
Poor community knowledge leading to inappropriate use

What happens if we do not do anything about this?

As time goes by, microbes will become more and more resistant to antibiotics and we will return to the era before antibiotics were discovered. More and more infections will become untreatable. The costs will escalate (Figure 3).

Figure 3

Source : Public Health England, Health Matters : Antimicrobial Resistance

https://www.gov.uk/government/publications/health-matters-antimicrobial-resistance/health-matters-antimicrobial-resistance.

Strategies to address the problem