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Antibiotic resistance explained: Why your decisions matter in the fight against superbugs

ABC News logo ABC News 6/05/2016
Taking antibiotics increases your risk of having resistant organisms in your body by about 50 per cent. © ABC News Taking antibiotics increases your risk of having resistant organisms in your body by about 50 per cent.

We've all faced the "cold conundrum" on occasion. Should you resign yourself to feeling like rubbish for a week or more while your body fights off the bug?

Or try and nip it in the bud with some drugs? Antibiotics can seem like an easy solution. The problem is, just one packet can have an impact on your body's ability to fight disease the next time you get sick.

It can also compound antibiotic resistance at a community level — contributing to the creation of antibiotic resistant superbugs, which can be very hard — if not impossible — to treat.

How does antibiotic resistance occur?

Allen Cheng, professor of infectious diseases and epidemiology at Monash University, said when you take antibiotics to treat an illness the aim is to target the bacteria causing your illness.

But the antibiotics may not kill off all the bacteria causing your illness. Professor Cheng said most bacteria have a short lifecycle and the opportunity for genetic change and mutation is high.

"There's a chance that one, or two, or 10 or 50, have some sort of mutation that gives them resistance to antibiotics," Professor Cheng said.

"They grow up and that's sort of like natural selection at work. So you've killed everything else off and what's left over is stronger than what was there before. And so that's how antibiotic resistance starts."

Can one pack of antibiotics make a difference?

The short answer is yes.

One packet of antibiotics can affect the level of drug resistant bugs in your own body and can also contribute to the broader issue of antibiotic resistant disease, at a community level.

At an individual level, when you take antibiotics it is not just the bacteria that is making you sick that are affected.

"If a particular person takes antibiotics and we might be targeting, say, a urinary infection ... The antibiotics don't just go to the urine, they go to all parts of the body and can impact on the bacteria that are present in other parts of the body, like your gut and your nose and so on," Professor Cheng said.

So you're potentially creating a range of different drug resistant organisms.

Professor Cheng said studies have found that after just one course of antibiotics, the risk of having antibiotic resistant organisms increases by roughly 50 per cent.

The studies tested the level of antibiotic resistant bacteria in each participant's system before taking antibiotics, and again after taking them.

"[Researchers] say 'OK how many of them had [antibiotic resistant bacteria] before you started?'," he said. "And then they give them antibiotics and say 'how many of them have [antibiotic resistant bacteria] after you have antibiotics?' And that risk is about roughly double ... for up to six to 12 months."

Each time you take antibiotics, the level of resistant organisms in your system potentially increases. Professor Lyn Gilbert, an infectious disease expert and microbiologist from the University of Sydney, explained that antibiotic resistant organisms usually accumulate in the body over time.

"It's a quantitative thing ... the more [antibiotics] you use, the more chance there is that a mutation will occur or a resistance gene will spread from one organism to another ... It's a sort of slow incremental thing," she said. "It doesn't happen dramatically but it happens over a long period of time."

Antibiotics also affect 'good bugs' in your system

Because antibiotics work on a range of bacteria in the body, Professor Gilbert said taking them can also affect your body's natural defences to bacterial infection — like the good bacteria in your gut.

This can then make you more susceptible to antibiotic resistant bacteria spread by other people.

"People who become colonised with these multi-resistant [antibiotic resistant] organisms can spread them to others and that particularly happens of course in hospitals, where a lot of people are on antibiotics," she said. "If you're on antibiotics, your normal bowel flora is suppressed, and so that means that multi-resistant organisms have a sort of opening to colonise the gut, while you haven't got all your normal bowel flora."

She said sometimes your own natural gut flora can even mutate and become resistant inside you.

"But it's probably more common the other way round — that you just knock off all your sensitive organisms and then you become colonised with someone else's," she said.

Does stopping antibiotics early contribute to resistance?

A common misunderstanding about antibiotic resistance is that it is primarily caused by people not taking the full course of drugs prescribed by their doctor — essentially knocking out some of the bacteria, but leaving behind drug-resistant organisms.

But Professor Gilbert said this was not strictly true. "It's a bit of a myth that if you don't finish your course you're more likely to get resistance," she said.

"In fact, if you take a short course you're actually less likely to get resistance; because the longer you take them the more likely it is that resistant bugs will develop."

Professor Gilbert said even when antibiotics were used properly drug resistant bugs were likely to be left behind. "It's just that ... if you're going to otherwise die from an infection then the risks of using antibiotics are obviously a lot less than the risk of dying from infection," she said.

Overuse is the primary issue

Professor Gilbert said at a community level the primary issue was the overuse and inappropriate use, of antibiotics.

This includes people being prescribed antibiotics for mild bacterial infections that their bodies are capable of fighting without drugs — and also for viruses (like the flu), which cannot be fought with antibiotics.

In Australia we have one of the highest antibiotic prescription rates globally, with around 29 million prescriptions issued annually, according to Pharmaceutical Benefits Scheme data from 2013.

More alarmingly, research by NPS Medicinewise suggests one in five people expect antibiotics for viruses like a cold or flu, and that 57 per cent of GPs will prescribe antibiotics for an upper respiratory tract infection — just to meet patient expectations.

Audits of antibiotic use in Australia have indicated that between 30 and 50 per cent of antibiotic prescriptions are either not consistent with guidelines, unnecessary, or the incorrect drugs were prescribed.

"So there's no doubt that there's a lot of inappropriate use," Professor Gilbert said. And again — once people become colonised with antibiotic-resistant organisms, they can then spread them to others, which deepens the issue for the general population.

Where does Australia stand with 'superbugs'?

In recent years, the message about the dangers posed by antibiotic resistant bugs has increased in urgency.

The World Health Organisation warned of a "global crisis", saying the overuse of antibiotics was fuelling dangerously high resistance levels and the creation of superbugs.

A review into antimicrobial resistance commissioned by the UK Government in 2014 found that if left untreated, antibiotic resistance could lead to 10 million deaths a year worldwide by 2050 — costing the world roughly $1.3 trillion.

One of the main types of multi-resistant organisms found in Australia are the bugs that cause staph infections, which can be found both in hospitals and in the community.

But fortunately, so far Australia has managed to avoid some of the other superbugs that have become prevalent overseas. One type of superbug Australia has managed to keep under control is multidrug-resistant tuberculosis.

Once considered manageable with antibiotics, drug-resistant strains are on the rise again in developing nations, particularly in sub-Saharan Africa.

But superbugs have even become an issue in developed countries like the United States, where some types of multi-resistant bacteria are a bigger problem than in Australia.

"In the USA ... they've been much more liberal with the use of antibiotics in animals, whereas we've banned quite a few in the last 20 to 30 years in Australia, and so we haven't had such a problem," Professor Gilbert said.

She said in developing countries, a lack of antibiotic regulation and poor sanitation meant super bugs were more common than in Australia.

"In places like India and many South-East Asian countries there's ... wide availability of antibiotics over the counter and often poor quality," she said. "But poor sanitation just means that the water gets contaminated and multi-resistant organisms spread from people to people."

Doctors rely on antibiotics for major surgeries

Professor Cheng agreed Australia does not have high rates of antibiotic resistance compared to many other countries.

"But that doesn't mean that we can't do better and prevent this being a problem in the future," he said.

Professor Cheng said in a hospital environment doctors used antibiotics for a variety of reasons — and not just to treat patients who presented with infections.

"There are a lot of things that are done to patients that we rely on antibiotics ... for example having a hip joint replacement or a knee joint replacement," he said.

"All that is possible because we have antibiotics that can prevent or treat infections that may be a consequence of that. The same with transplants and cancer chemotherapy."

He said one big worry with superbugs is that if doctors don't have antibiotics at their disposal, things like hip replacements are suddenly much more dangerous than they would otherwise be — which is why it is so important to antibiotics responsibly.

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