
Professor Michael Gillings is an evolutionary biologist at Macquarie University in Sydney. He speaks to Mary Murray and Satya Sivaraman about the need to take a fresh look at current approaches to the phenomenon of antibiotic resistance.
How useful is the ‘war’ metaphor as a way of understanding human relationships with bacteria?
We have the common perception that bacteria are the enemy. There are actually only some bacteria, in fact very, very few bacteria, that are dangerous to humans. The overwhelming majority of bacteria are good for us. If bacteria were to disappear from human environments, everything would close down – everything would stop. Our health is dependent on the bacteria in us and on us. Our food production is dependent on bacteria: in fermentation, to make bread, coffee, chocolate and beer, etc. So, to me, the war metaphor is not a good one.
What are the new ways of seeing microbes that are currently emerging?
One of the things we need to bear in mind is that the planet as a whole is driven by a cycling of nutrients, like sulphur, phosphorous, nitrogen and carbon. Micro-organisms supply most of these services – such as the oxygen we breathe, the recycling of cellulose into usable forms of carbon, the cycling of sulphur, the production of nitrogen for plant growth and fertilisation. If you take all these services – called eco-system services – and add up the value of these to humans, it will come out to something like USD 35 trillion a year. This is three times the gross domestic product of all the countries in the whole world combined. And, surprisingly, that estimate was first made only in 1997. Micro-organisms are the good guys.
What happened to the natural immunity of human beings to pathogenic bacteria? Why has that changed?
One of the problems we have is that we are actually not dirty enough. Growing up in too clean an environment means that the immune system, one could say, is searching for things to react to. It has not had enough exercise to mount the immune responses it is supposed to, so it mounts inappropriate responses instead. Allergies, asthma and so on are the result. The immune system is reacting to things it shouldn’t be reacting to. It may be that, like peanut hypersensitivity, or sensitivity to shellfish, nickel, milk and so on, our immune systems are not sufficiently trained early enough. So when babies are eating snails and shovelling dirt into their mouths, it is probably a good thing.
Is it ever possible to block antibiotic resistance forever?
Firstly, we can realise that any individual antibiotic or disinfectant has a shelf life [when its effectiveness expires]. It will only work for so long. Gradually, more and more things will become resistant to it. We need to think about how to use them in a way that minimises the appearance of resistance. In order to do that, we need to understand how resistance arises. Where are the genes coming from, and where they are going to? How and how long are we using it? In what context, and for what disease? That is the highest priority: to preserve what we already have, while we are to discover new agents and then preserve them.
What about the search for new antibiotics? We see this as our main priority – is this wise?
I would say instead that the use of antibiotics should be the last resort. We use antibiotics frivolously. We use them for conditions that are actually not bacterial at all. We use them in our domestic animals and plants. We used to spray our apple trees with antibiotics to control bacterial diseases. That is just a disaster waiting to happen. The other point that I would like to make is a social one. Antibiotic resistance is a global problem. It will be one of the major obstacles facing human medicine and disease control over the next 20 years. So everyone has to do something about it.
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