Tag Archives: antimicrobial resistance

“No Pressure”

Have you ever taken yourself, or one of your children, along to a doctor and then either exaggerated the presenting symptoms in order to increase the chances of being prescribed an antibiotic?

Or have you ever directly asked the doctor to prescribe an antibiotic, either subtly or not so subtly…?

I am guilty as charged, because I am human like everyone else. However I am improving now that a large part of my job is anti-microbial stewardship!

And because doctors are human as well, they often give in to such demands, because they want the patient to leave the consultation having had a positive opinion of them, even if the antibiotic itself will make no difference to the outcome or speed of resolution of infection.

This week is World Antibiotic Awareness Week, an initiative by the World Health Organisation to make people aware of the potential dangers of overuse of antibiotics. There is plenty of useful promotional material available on their website to promote this message.

However, I believe that creating a “No pressure” culture is one of the key elements of antibiotic awareness amongst the general public. This is the concept of allowing your doctor to make an objective decision as to whether an antibiotic is required. I.e. you go to your doctor, relate the symptoms to them as honestly as possible, you do not pressurise the doctor for any particular type of treatment , and accept whatever treatment choices that the doctor makes.

As most of you are aware, antibiotics are completely futile for many of the conditions that a family doctor will see each day.

An antibiotic prescription in general practice should be the exception, not the norm.

Amidst all the various components of antimicrobial stewardship, I believe the key is reducing antibiotic usage by reducing inappropriate or unnecessary antibiotic prescriptions.

This is not just the responsibility of doctors, but of patients as well.

By all means, go to your doctor, but don’t go in the expectation that you will receive an antibiotic. If you end up getting one, so be it, but don’t push for it.

No pressure…



I get the occasional anxious phone call from clinicians concerned about the “rising rates ” of trimethoprim resistance to E. coli…

Not being entirely convinced, I did a (20 year) search for E. coli resistance to trimethoprim at my lab, analysing over 2 million isolates, and came up with the following graph.



I couldn’t work out how to insert a trendline into the graph (I am so useless…), but I think you will agree that it is going to be fairly flat.

The antibiotic apocalypse is not arriving in New Zealand anytime soon. In fact the whole concept of “antibiotic resistance” as perceived by the public is horribly generic and oversimplified…

This example above of course is just one microbe/antimicrobial combination out of many hundreds that could have been analysed, but the observation did highlight a couple of things to me:

  • If antibiotic usage is relatively constant in a population over a prolonged period of time, then antimicrobial resistance does not necessarily rise inexorably. (q.e.d.)
  • Always back your claims up with objective data wherever possible. It is the trends which are critical in the surveillance of antibiotic resistance. We are lucky that at my lab we can now search back through 20 years of electronic data. Before 1996 the data was paper based (and likely lost in a basement or incinerated by now!)

If you did a similar exercise for all the possible microbe/anti-microbial combinations (I just might if the Christmas holidays are quiet!), you will find some trends that are upwards, some that are static, and some where the resistance rate is trending downwards.

A bit like Twitter really….

So when someone says to you. “Antibiotic resistance is increasing all the time. In 10 years time, all infections will essentially be untreatable” (I really detest this type of generic, off the cuff, unsubstantiated statement…)

…you should respond with something along the lines of “Exactly which microbe and antimicrobial combination are you talking about?” and “Show me your data…”.

Some infections will be, and already are, untreatable (mostly due to extreme and focused selection pressure), but the chances of a whole bacterial species becoming pan-resistant are remote. There are two main reasons for this. i) Bacteria survive in open systems, and ii) Bacteria need to expend energy to become resistant.

But these are other stories altogether…


“Defying Nature”


I occasionally hear people/experts saying that antibiotic resistance can be acquired by bacteria without any cost to the ‘fitness’ of the organism (i.e. it’s ability to replicate and survive in a competitive environment)

I could not disagree more…

If antibiotic resistance could be acquired without any cost to fitness, I think all the human bacteria (as well as all the environmental ones) would be pan-resistant already. It just doesn’t make sense to me.

Bacteria are masters of survival. They are also hyper-efficient, and need to carefully budget their energy quota not only on defence, but also on attack and redeployment, not to mention communication. If the bacterial population does not need to be resistant in a particular environment, it will not waste its precious energy on resistance genes for a “Just in case” scenario.

Most in-vitro studies show that acquisition of antibiotic resistance does indeed have a fitness cost. A few don’t. For those exceptions I would offer the following explanations:

  • Just like anti-microbial susceptibility testing, I suspect that in-vitro bacterial fitness correlates only roughly with in-vivo fitness.
  • The fitness cost may be so miniscule, that it is impossible to demonstrate in the laboratory setting.

So in an antibiotic free environment, the susceptible strain will eventually win out over the resistant one. This might take days, or it might take decades, depending on the relative fitness difference. The fitness gap between susceptible and resistant strains might also be narrowed by compensatory mutations, but it will never be zero. It is all just a matter of time, evolutionary time…

If a bacterium doesn’t need to be resistant, then it won’t be, and it will eventually dispose of the means to be resistant.

Bacteria are lean, mean, replicating machines. They are also highly obedient to the Laws of Evolution…


For a nice article on the above concept, with a few references attached, click here. About a 5 minute read.