By Siouxsie Wiles 24/11/2016


antimicrobial resistanceLast week was World Antibiotic Awareness week, an initiative of the World Health Organization (WHO) to raise awareness and understanding of antimicrobial resistance. To follow-up, here at Te Pūnaha Matatini we are having a week-long conversation about the health, social, economic, and environmental impacts of infectious diseases in Aotearoa New Zealand. In this post, I want to touch on what antimicrobial resistance is, and what a future without antimicrobial medicines could look like.

What is antimicrobial resistance and what is causing it?

Antimicrobials are chemicals that kill or stop the growth of microbes. But as microbes is the generic term for a multitude of life forms which differ in their genetic make-up, life-styles and habitats, so antimicrobials can be divided into different categories depending on what they target. Some antimicrobials work against all microbes, but others are more specific. Antivirals only work against particular viruses, antifungals only work against particular fungi and antibiotics only work against particular bacteria.

Antimicrobial resistance is when microbes develop the ability to stop antimicrobials from affecting them. As most microbes replicate themselves and their genetic material fairly rapidly (some can divide in just a few minutes), and they can grow to large numbers (easily reaching population sizes in the billions if they have the right conditions), there are plenty of opportunities for resistant mutants to arise purely by chance. These mutants can then grow quite happily in the presence of the antimicrobial. This happens wherever microbes encounter antimicrobials – in human and veterinary medicine, in agriculture, but also in sewage systems and out in the wider environment.

More worryingly is when microbes gain the ability to share resistance between each other on mobile bits of genetic material. Then they don’t even need to be in the presence of the antimicrobial agent – they just need to meet the right kind of resistant microbe!

A major factor in the development of resistance is the misuse and overuse of antimicrobials. So being used when they aren’t needed, or not being used correctly. Another worry is the use of similar antimicrobials in human medicine and in agriculture. For example, a fungus commonly found in soil has become resistant to the antifungal pesticides used in gardening and agriculture. Because similar antifungals are used in human medicine, these resistant fungi are now able to cause almost untreatable infections in some vulnerable hospital patients. And these patients can become infected just by being in a bed next to an open window that looks out onto a garden!

Is antimicrobial resistance something we should be worried about?

Yes. Experts predict that within the next decade we will run out of antimicrobial medicines to treat many common infections. Part of the reason we are in this position is that most of the pharmaceutical industry pulled out of antimicrobial research decades ago, so the medicine cupboard is basically empty. Similarly, the vast majority of government and charity funding around the world has gone on researching non-communicable diseases. Any new antimicrobial compound discovered today could take a decade of development and testing before it would be available for doctors to use. The situation is a catastrophe on a par with global warming.

What are the most concerning examples of resistant strains of infectious diseases?

The major resistant bacteria that are circulating around the world are extended-spectrum beta-lactamase (ESBL) expressing strains of Escherichia coli and Klebsiella pneumoniae, which are of particular concern in hospitals, and some strains of Mycobacterium tuberculosis which causes the lung disease TB. There are an increasing number of strains of these bacteria that are sensitive to just one or two antibiotics, and some strains that are pretty much untreatable. Another resistant organism of growing concern globally is Neisseria gonorrhoeae which causes gonorrhoea. While most men with gonorrhoea will have symptoms when they have the disease, half of women can be asymptomatic so won’t know they are infected. Importantly, untreated gonorrhoea can lead to infertility.

What’s happening in New Zealand?

We wanted to show you the data, but can’t. It is publicly available on the web but Figure.NZ were denied permission to turn it into nice charts for you to see. What we can say is that the extremely resistant strains of E. coli, K. pneumoniae and M. tuberculosis we see here are mainly coming into New Zealand from countries like India, China, and those in south-east Asia. This is going to be an area to watch, especially given the importance of countries like China for trade and tourism in New Zealand.

N. gonorrhoeae is also one for us to watch as highly resistant strains have been reported in Australia. In New Zealand, gonorrhoea is not a notifiable disease so the only data we have is based on the voluntary provision of the numbers of diagnosed cases from laboratories and sexual health and family planning clinics. In 2014, that number was 3,038, with 977 of these cases in young people under the age of 19. Less than half of sexually active young people report using condoms which would protect them from infection. If we end up with a completely untreatable strain of N. gonorrhoeae taking hold in New Zealand this could have a huge impact on our future fertility.

The last organism of concern here is Methicillin Resistant Staphylococcus aureus (also known as MRSA) which is very much a problem of our own making. Over the last few years there has been a huge increase in the number of skin and soft tissue infections caused by S. aureus in New Zealand (1). Alongside this, there has been a huge increase in prescriptions for a topical antibiotic called fusidic acid. As a consequence, one of the major clones of S. aureus now causing disease in New Zealand is an MRSA clone which is resistant to fusidic acid (2).

Major misconceptions about antibiotics

There are a number of major misconceptions about antibiotics. Lots of people don’t know that bacteria and viruses are very different life-forms. This means that antivirals don’t work on bacteria, and antibiotics don’t work on viruses. In countries where antibiotics are available without prescription, many people confuse antibiotics with pain-killers, so will take antibiotics for things like a headache!

Another common misconception is that it is us that become resistant to antibiotics, rather than the microbes. Perhaps this is a misunderstanding between how antibiotics work (by killing the bacteria directly), versus what happens when we are vaccinated (our immune system is primed to recognise and fight off the invader).

But the biggest misconception is that people who don’t take antibiotics, or who take them very rarely, won’t be affected by antibiotic resistant bacteria – that the antibiotics will still work for them. It doesn’t matter if you’ve never had a course of antibiotics, or if you’ve had several, it all depends on the bacteria you get infected with. Similarly, healthy people who have never had a course of antibiotics could still have antibiotic-resistant superbugs living happily up their noses or in their guts. They can easily spread from person to person, or can be picked up while travelling overseas.

What does a future without antimicrobials look like?

A future without antimicrobials will affect us all; rich and poor, young and old. In a world without antimicrobials, previously treatable infections will once again become deadly, or may require amputation to stop them in their tracks. Because antimicrobials are also used to prevent infection in vulnerable people, it will also become life threateningly risky to do routine operations like caesarean sections and joint replacements, and treatments like chemotherapy for cancer.

Margaret Chan, Director-General of the World Health Organization, called antimicrobial resistance “…the end of modern medicine as we know it”. In a series of reports commissioned by the UK’s former Prime Minister David Cameron, economist Sir Jim O’Neill has estimated that without urgent action, antimicrobial resistance will kill 10 million people a year by 2050, more than will die from cancer. O’Neill has also put an economic cost on the issue, estimating that inaction will cost the world’s economy 100 trillion USD by 2050.

What should we be doing to combat antimicrobial resistance?

Combatting antimicrobial resistance requires a global effort to stop the overuse and misuse of antimicrobials in human and veterinary medicine, and in agriculture. It requires governments, philanthropists, charities and industry to invest serious money into antimicrobial discovery and development and research into new ways to combat infectious diseases. We also need quicker and better ways to diagnose infectious diseases so that patients can receive the right treatment as soon as possible.

Equally important is that we have a national conversation about how we all, the public, health workers, policymakers and the agricultural sector, can contribute to solving this global crisis from right here in New Zealand. I hope you’ll participate in this important discussion. Follow #infectedNZ on Twitter or Facebook, or leave a comment below.

References:

  1. Williamson DA, Zhang J, Ritchie SR, Roberts SA, Fraser JD, Baker MG (2014). Staphylococcus aureus infections in New Zealand, 2000-2011.Emerg Infect Dis. 2014 Jul;20(7):1156-61. doi: 10.3201/eid2007.131923.
  2. Williamson DA, Monecke S, Heffernan H, Ritchie SR, Roberts SA, Upton A, Thomas MG, Fraser JD (2014). High usage of topical fusidic acid and rapid clonal expansion of fusidic acid-resistant Staphylococcus aureus: a cautionary tale. Clin Infect Dis. 2014 Nov 15;59(10):1451-4. doi: 10.1093/cid/ciu658.

About:

Dr Siouxsie Wiles is Acting Deputy Director of Te Pūnaha Matatini. She describes herself as a microbiologist and bioluminescence enthusiast. Head of the Bioluminescent Superbugs Lab at the University of Auckland, Siouxsie combines her twin passions to understand infectious diseases.

This article was originally published on Te Punaha Matatini as part of InfectedNZ – an online campaign to raise awareness about infectious diseases and antimicrobial resistance. Read the original article.