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Fears about antibiotic resistance have opened up a can of germs

We’re frequently confronted with doom and gloom stories about the antibiotic crisis. As antimicrobial resistance grows, and the pipeline of new antibiotics shrinks, there may soon be nothing left on pharmacists’ shelves to treat some infections.

Overuse of antibiotics is to blame. A report published in 2016 by the Australian Commission on Safety and Quality in Health Care claimed Australia has among the world’s highest antibiotic prescribing rates along with very high rates of community resistance to vancomycin, one of the last lines of antibiotic defence.

So something needs to be done.

There’s the traditional advice. Doctors need to desist from prescribing antibiotics for viral infections (they don’t work) and restrict prescriptions to clear bacterial infections. They should prescribe the oldest, cheapest antibiotics, which are actually still effective for most infections. Given resistance inevitably emerges a few years after a new antibiotic is introduced, the latest weapons in the arsenal, like vancomycin, need to be held in reserve for as long as possible.

But now there’s a new piece of advice – and it’s contentious. In the July 2017 edition of the British Medical Journal, some experts argued that patients should stop following the time-honoured instruction to “complete the course” of prescribed antibiotics.

The idea you should chuck the antibiotics once you’re feeling better, though, has riled other experts who say there is still good reason to follow the traditional advice.

The original idea of staying the course on antibiotics, paradoxically, was to prevent resistance by killing off every last offending germ. According to this view, the germs that took the longest to die were likely to be the most resistant.

The proponents of “not finishing the course” say it is the exact opposite. There is little evidence that the longer you stay on the course the more likely you are to kill off all the germs. Instead, it is the prolonged exposure to antibiotics that fosters the evolution of resistance in the microbial communities we host. As sensitive bacteria are quickly killed off, it is the microbes with inherent resistance that gain the advantage and multiply. So stopping early is good, proponents say, because it removes the evolutionary pressure on the microbial communities.

The traditionalists say that only taking antibiotics till you feel better is simplistic and risky for a variety of reasons. For one thing, for some conditions there is evidence the bugs can bounce back if the course of treatment is too short. Tuberculosis, for example, needs months of treatment. The same may be true for Staphylocuccus aureus (golden staph). For another, a blanket recommendation to stop taking antibiotics earlier doesn’t take account of variations in the effectiveness of different antibiotics that work in different ways over various time spans.

For several conditions the needed antibiotic treatment duration is actually shorter than what we once thought.

As is often the case in medicine, debates like this leave you and me confused about the right thing to do. The trouble is there is not enough data to enlighten us. There is, though, some evidence that can be brought to bear.

It turns out that for several conditions the necessary treatment duration is actually shorter than what we once thought. For instance, while the vast majority of sore throats are viral and therefore not helped by antibiotics, a small proportion are caused by bacteria such as streptococci (strep). When I was a medical student we were taught you needed at least 10 days of penicillin to treat a strep throat. Now the evidence with newer antibiotics is that three to six days are enough in otherwise healthy kids.

Another example is a lower urinary (bladder) infection. A review of the evidence suggests three to six days are as effective as longer courses. In children it is even shorter – two to four days.

Experiments in piglets have found that such a reduction in antibiotic duration could reduce the excretion of resistant germs in faeces by 75%.

With otitis media (middle ear infection) there is questionable evidence that the routine use of antibiotics is beneficial at all.

On the other side, the evidence suggests that the ulcer germ Helicobacter pylori (which increases the risk of stomach cancer) requires 14 days of antibiotic therapy to be eliminated. So rather than blanket pronouncements on finishing or not finishing a course, doctors and patients need better evidence and confidence as to what length of course is actually effective for a particular illness.

This article appeared in Cosmos 76 – Spring 2017 under the headline “Staying the antibiotic course”

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