Why we should learn to love bacteria: It's time to go easy on the antibac spray

We’re obsessed with all things antibacterial, but new research shows that tackling bacteria harms the good as well as the bad and can make us fat, ill and asthmatic, says Adriaane Pielou

 Micrococcus Luteus bacteria

 Micrococcus Luteus bacteria

Bacteria are our friends. Honestly. Most of them, anyway. As one of the earliest life forms on the planet, able to live anywhere – including on our skin, in our mouths and in our gut – they’re arguably our oldest, closest friends. You don’t kill your friends, even if they’re wriggling little life forms visible only when gazed at through a microscope. It’s self-defeating. And when it comes to bacteria, new research shows that killing them can make you fat, ill, and cause your children to be asthmatic.

Some bacteria, of course, deserve to be hunted down and killed – flesh-eating necrotising bacteria in particular, now highly resistant to our most powerful antibiotics. But from what scientists now know, it’s clear that the scattergun attacks we’ve been mounting on our bodies’ resident bacteria – great colonies of which call us ‘home’, reproducing every 20 minutes – look decidedly misguided.

So a dramatic shift in thinking is in order. It’s time to stop equating all bacteria with dirt, danger, death and decay, stop the overuse of antibiotics, which kill off friendly and unfriendly bacteria alike. Stop squirting antibacterial sprays around. These usefully kill nasty E coli bacteria left on the chopping board by raw meat or chicken, but it’s now known that they also kill the bacteria that protect small children from developing allergies such as psoriasis, eczema and asthma.

It's time to stop equating all bacteria with dirt, danger, death and decay 

And we should even stop cleaning ourselves so fiercely. Harsh cleansers, toners and chemical-laden shampoos can kill off the protective friendly bacteria on our skin and scalp, allowing unfriendly ones to proliferate. Flaky, dry patches, areas of sensitivity and acne show precisely where they’re taking up residence. In fact, in the US you can now buy spray-on bacteria to recolonise your skin with the good guys.

Bacteriological research that has been taking place recently marks the first time in history that scientists have been able to study the tens of thousands of species of bacteria that live on us, not just the tiny proportion that can be cultured in a petri dish. Until recently, that had been pretty much all that could be studied since the invention of the microscope in the 17th century. These groundbreaking studies are ongoing, but they kicked off with the European MetaHIT and, in the US, the Human Microbiome projects, which saw several hundred scientists around the world studying bacteria samples taken from 17 different parts of the body from around 375 volunteers. The research took place thanks to the complex DNA-sequencing computer programmes developed for the Human Genome Project, which in 2012 completed the sequencing of all 22,000 human genes.

One of the key revelations is how outnumbered we now know we are by our bacteria. Starting at birth, when we pick up bacteria from our mothers, our microbiome – the collective name for the 100 trillion bacteria that live on us – is usually established by the time we are three years old, and consists of anything from 2,000 to 10,000 different species, each with about ten times the number of genes (and thus potential capabilities) that we have.

Most of these bacteria live in our gut. The existence of gut bacteria has been known since the 1860s, when the French chemist Louis Pasteur, father of modern microbiology, was experimenting with what would become known as pasteurisation. These days most of us are aware that friendly gut bacteria are important to good digestion, good digestion is crucial to health, and that antibiotics kill off those friendly bacteria. We probably know, too, that unless we repopulate our gut after a course of antibiotics (with the right food plus bacteria-containing probiotics or bacteria-stimulating prebiotics) the result may be gas, bloating and constipation (the curse of so many hospital patients), followed by lowered immunity.

'Chemical-laden shampoos can kill of our friendly bacteria, allowing unfriendly ones to proliferate'

'Chemical-laden shampoos can kill of our friendly bacteria, allowing unfriendly ones to proliferate'

But a fascinating revelation of this new research is how about 60 per cent of the immune system itself consists of those friendly gut bacteria. When antibiotics destroy the good guys in our gut, unfriendly bacteria – no longer being kept in check – feast on putrifying or indigestible food particles, causing that gas and bloating.

Then, if those putrefying or indigestible food particles, now loaded with unfriendly bacteria, surge past the dead good guys through our weakened, undefended gut walls and get into our blood they can surprise and overwhelm colonies of other bacteria that are ill-equipped to fight them. Result: bad breath, headaches, lactose intolerance, candida and a range of possible illnesses – from that catch-all irritable bowel syndrome to auto-immune diseases such as rheumatoid arthritis. Meanwhile, if C difficile bacteria (which commonly affects people who have been treated with antibiotics) has been left untrammelled in the gut, it can kill off everything around it with its toxins.

Blaming a lack of friendly bacteria for obesity, too, might sound far-fetched. Yet it turns out that one particular bacterium, H pylori, almost always present in the guts of healthy, slim people, has been found to be absent in the guts of very overweight people.

H pylori (discovered only in 1983, which tells you how new most bacteriological research is) can cause ulcers. But it also helps signal when we’re full. No H pylori means no message of ‘enough with the cake’.

And how, you ask, might friendly bacteria revolutionise healthcare? Look away now if you’re eating. Faecal transplanting – yes, that means friendly-bacteria-laden poo from a healthy person being fed into the gut of an unhealthy one – has proved so successful in recent test cases that it may become more common. The technique has worked brilliantly in most of the patients on whom it has been tested as a last-resort measure – easily outperforming antibiotics in tackling C difficile, for instance. In future, doctors may routinely sample your gut bacteria to aid diagnosis. (Private faecal analysis is already available, with companies such as Biolab charging from £96 per test.)

Bacterial battle tactics may also help win the crucial fight against infections resistant to all current antibiotics. Exciting new research is already building on the recent discoveries in the labs at Imperial College, London, that some bacteria kill rivals by firing toxins into them to degrade their DNA, while others resist antibiotics by ‘lying low’, so that the antibiotics, which work by sensing their targets’ activity, can’t detect them. Led by Professor David Holden, Imperial’s researchers are exploring how these tactics might usefully be hijacked, mimicked or blocked.

Meanwhile, around the world bacteria are already beavering away on our behalf in myriad other ways: consuming oil spills, turning food waste into biogas, converting revolting public-loo smells into tolerable scents (a true triumph), reducing plumbing bills by devouring drain-gunk. Bad-bacteria-killing sprays used to coat entire buildings – produced by the US firm Pureti and in Japan credited with blocking a Sars outbreak afflicting much of the rest of Southeast Asia – offer thrilling possibilities. As does the discovery this year by Professor Bill Keevil and his team at the University of Southampton that lethal MRSA bacteria, scourge of hospitals, survive for weeks on stainless steel, commonly used in hospitals, but are dead within eight minutes on copper surfaces – wa-hey! The future is bright and bacterial. As long as we look after our little friends.

LET FRIENDLY MICROBES FLOURISH... 

  • Nurture your friendly bacteria. Eat the natural foods they flourish on – vegetables, nuts, avocados, fermented items such as live yoghurt, miso and sauerkraut. Take pre- and probiotic supplements.
  • Avoid the foods that unfriendly bacteria thrive on, such as sugar, meat and processed items.
  • Avoid antibiotics unless they’re crucial (they cannot kill viruses).
  • Eat organic. Non-organic meat, poultry and salmon are often dosed with antibiotics to aid growth and curb infection.
  • If you’re feeling brave, try testing the theory that bacteria help us self-clean. Michael Pollan and Julia Scott’s accounts (at nytimes.com) of giving up all body cleansers make intriguing reading.
  • Try friendly-bacterial products, such as drain cleaners (at amazon.co.uk).