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Antibiotics and resistant bacteria

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KMatey
867781.  Wed Nov 30, 2011 4:54 pm Reply with quote

In the 2nd book of General Ignorance, At the end of the section "What effect does drinking alcohol have on antibiotics?", the authors claim that over-prescription stops antibiotics from working. I think this is a myth, put about by someone who wants to save money in the short term for the NHS. If you think about Darwin's "natural selection" explantion of evolution, an organism cannot willfully change its genetic characteristics to adapt to its environment (except perhaps for humans nowadays). All it can do is generate random and spontaneous differences in its characteristics, and it is the environmental conditions (in this case the presence or not of various antibiotics) which do the selection, usually over a very long time. Because the mutations occur spontaneously and randomly, the emergence of a resistant strain will occur randomly on a date which although unpredictable, will just happen anyway and will not be hastened by having a larger amount of prescriptions written. In fact, the converse may be true, perhaps it would be better to flood the world with antibiotics in an attempt to kill off the evil bacteria before they can mutate sufficiently to resist. The more we can kill off now, the less of them there willl be around and so the less opportunities for mutation. The only drawback with my total anihilation idea is we might also kill off all the "good" bacteria. Perhaps some happy medium needs to be calculated, where we hinder the bad ones without harming the good ones too much. But I still think that "Over-prescription causes resistance" is nobut a myth. What say ye?

 
Posital
867784.  Wed Nov 30, 2011 5:03 pm Reply with quote

Not over prescription - but not completing the course.

 
aTao
867792.  Wed Nov 30, 2011 6:26 pm Reply with quote

Over prescription can accelerate development of resistant strains, in fact it is likely to cause such changes to happen.
Consider a mutation that provides resistance to an antibiotic. It is likely that such a mutation will have some overhead, making such a strain less viable in a neutral situation. However if the antibiotic is present then the new strain will dominate.

 
Droid
867849.  Thu Dec 01, 2011 7:05 am Reply with quote

It's not just new mutations that cause the problems. There are a large number of plasmids which carry genes for producing resistance. These plasmids can transfer from one species of bacteria to a different one and then the resistance genes will be expressed in a different species. The presence of antibiotics creates a huge organic petri dish (or person) for selecting for the new resistant strains. The resistant strains have an advantage over those without resistance and so they grow. You then have a population with antibiotic resistance.
Beta lactamase, which breaks down penicillins, was discovered before penicillin went into widespread use. There are now many penicillin resistant strains of many species of bacteria which have only come to exist in the last fifty or so years since antibiotics were given out by doctors to people who really only had a bit of a bad cold.

 
CB27
867988.  Thu Dec 01, 2011 9:38 pm Reply with quote

When we think of mutations in DNA, we think of our genes, and how they are inheirted down the family. This is known as Vertical Gene Transfer.

However, what we've discovered in the past few decades is that Horizontal Gene Transfer not only exists, but is dominant in single cell organisms.

This means that when a mutation is successful in one cell, it can transfer that mutation to other cells nearby very quickly.

 
Awitt
921210.  Tue Jul 03, 2012 4:44 am Reply with quote

I have a nursing friend (no longer in that career though)who told me that in Aust. 20 + years ago they used to pour unused doses down the drain, leaving these bacteria in the drainpipe to adjust to the half-dose of drugs.
And yes, not completing the full course of antibiotics from our doctors doesn't help. Golden staph. and other scary bugs are thought to have originated from misuse/overuse of antibiotics. some people don't seem to realise that drugs are no use on viruses.

 
Posital
921330.  Tue Jul 03, 2012 12:42 pm Reply with quote

Awitt wrote:
some people don't seem to realise that drugs are no use on viruses.
So are all these useless?

 
Iconoclast24601
922511.  Sat Jul 07, 2012 11:28 am Reply with quote

KMatey wrote:
What say ye?


Antibiotics are the main cause of antibiotic resistance. Evolution is not just about random mutations, but also the environment that selects among them. Mutations that cause antibiotic resistance cost resources and opportunities that could have been spent elsewhere. In absence of antibiotics, these mutations do not thrive because they are useless dead-weight, and will lose in competition with more unencumbered non-resistant strains. Antibiotics reverse the situation.

Save your antibiotics, because if you use them now while they're not needed, they may not work when you do need them.

Source: I am a doctor


Last edited by Iconoclast24601 on Mon Jul 09, 2012 8:15 am; edited 1 time in total

 
Spud McLaren
922525.  Sat Jul 07, 2012 1:39 pm Reply with quote

aTao wrote:
Over prescription can accelerate development of resistant strains, in fact it is likely to cause such changes to happen.
Consider a mutation that provides resistance to an antibiotic. It is likely that such a mutation will have some overhead, making such a strain less viable in a neutral situation. However if the antibiotic is present then the new strain will dominate.
Iconoclast24601 wrote:
The danger of a TV show/forum specialising in "quite interesting" and non-intuitive facts is that it becomes all too easy to drift into trivial hairsplitting and pointless technicalities, ultimately promoting rather than abating ignorance by merely replacing the "obvious but wrong" with the "more annoying but still wrong".
Only some of us are wrong. This is the case across all strata of society. Or was Andrew Wakefield a mere figment of the collective imagination?

BTW, welcome to the forums, Iconoclast!

 
Arcane
922680.  Sun Jul 08, 2012 9:45 am Reply with quote

I remember patients asking doctors for antibiotics to treat a cold.

 
gruff5
922730.  Sun Jul 08, 2012 3:12 pm Reply with quote

Awitt wrote:
I have a nursing friend (no longer in that career though)who told me that in Aust. 20 + years ago they used to pour unused doses down the drain, leaving these bacteria in the drainpipe to adjust to the half-dose of drugs.....


Hospital drainpipes may not only provide the curse, but also the cure.

In the USSR republic of Georgia, 20+ years ago, doctors first isolated bacteriophages from hospital drains, where they had evolved to feast on the bacteria-rich effluent.

Bacteriophages are viruses that devour bacteria and could provide relief to the possible end of the antibiotic age. They have the advantage that they are specific to the intended bacterial target (no side-effects to the patient) and evolve just as bacteria do and so can keep up with the bastards.

 
Iconoclast24601
922851.  Mon Jul 09, 2012 8:38 am Reply with quote

Quote:
Only some of us are wrong. This is the case across all strata of society. Or was Andrew Wakefield a mere figment of the collective imagination?

(Doctors were by no means intended to be exempt as targets of my overly offensive signature, written well after I should have been asleep. I daresay that Mr Wakefield's actions probably call for a different signature entirely...)
Quote:
Hospital drainpipes may not only provide the curse, but also the cure.

In the USSR republic of Georgia, 20+ years ago, doctors first isolated bacteriophages from hospital drains, where they had evolved to feast on the bacteria-rich effluent.

Bacteriophages are viruses that devour bacteria and could provide relief to the possible end of the antibiotic age. They have the advantage that they are specific to the intended bacterial target (no side-effects to the patient) and evolve just as bacteria do and so can keep up with the bastards.

Bacteriophages are quite interesting indeed, but it is unfortunate the human body will recognise them as foreign organisms and mount an adaptive immune response, essentially relegating bacteriophages to one-hit wonders. Furthermore, as natural organisms, it may be difficult for pharmaceutical companies to patent and commercialise such therapies.

 
Jenny
922883.  Mon Jul 09, 2012 10:25 am Reply with quote

Iconoclast24601 wrote:


Bacteriophages are viruses that devour bacteria and could provide relief to the possible end of the antibiotic age. They have the advantage that they are specific to the intended bacterial target (no side-effects to the patient) and evolve just as bacteria do and so can keep up with the bastards.

Bacteriophages are quite interesting indeed, but it is unfortunate the human body will recognise them as foreign organisms and mount an adaptive immune response, essentially relegating bacteriophages to one-hit wonders. Furthermore, as natural organisms, it may be difficult for pharmaceutical companies to patent and commercialise such therapies.[/quote]

I fear that it is the last sentence of your post that is the crucial one. However, difficult is not the same as impossible.

Bacteriophage therapy was being investigated heavily in the 1920s and 30s, but antibiotics promised more immediate usefulness, and bacteriophage research was then neglected. I suspect it will be the next thing to be explored when organisms become more resistant to antibiotics.

 
gruff5
1089871.  Sat Aug 16, 2014 5:49 am Reply with quote

I continue to be curious about the issue of AB resistance.

Surely maintaining resistance is costly to a bacterium (in genetic material, energy, biochemicals etc) and in the absence of the specific AB, those AB-resistant bacteria that mutate back to the original form will be more efficient and gain the advantage over the others.

So, I would think that with 22+ classes of antibiotics around for decades (which is like millions of years would 'feel' to mammals), then a steady-state situation would arise where resistance reaches a plateau and advances no further.

Thus, there would be no dramatic "age of end of antibiotics", just a generalised reduced effectiveness and a need to occasionally rotate around the AB classes to keep the germs on their toes.

Does such a concept of "resistance plateau" bear any resemblance to reality?

 
julesies
1090267.  Tue Aug 19, 2014 12:08 am Reply with quote

It is costly. If you do a simple competition experiment between one population that has antibiotic resistance and one that doesn't (in a non-selective environment, of course), the population without resistance will outcompete the population with it.

But there are a few reasons why a "resistance plateau" as you described wouldn't really occur.

First, a lot of antibiotic resistance genes are carried on mating plasmids. These plasmids are very easy to lose but also incredibly easy to gain and can spread through a population with selective pressure rather quickly.

Second, a lot of these resistance plasmids are present in bacteria in the soil because many of our antibiotics are fungal derived. So even if we rotate our antibiotics, resistance plasmids will be maintained by bacteria in the soil, and then could quickly spread through populations of pathogens. Also, a lot of the antibiotics we use end up in the soil and contribute to the problem.

Third, I don't think we really have enough antibiotics to rotate them. A lot of antibioitics are derived from each other, and some resistance mechanisms convey resistance to the entire group. Also, a lot of antibiotics are specific for a certain type of bacteria (Gram-negative, Gram-positive, or acid-fast), so that reduces your pool as well. Some antibiotics have terrible side-effects, too, so you wouldn't want to use them as a first resort. Take a MRSA infection as an example; you can use vancomycin, which is a great antibiotic, but it has potential side effects and must be taken intravenously, so a doctor wouldn't prescribe it for a non-resistance Staph infection.

Also, a major problem that this wouldn't address is the prophylactic use of antibiotics on a large scale in farm animals. This contributes hugely to the resistance problem.

These are the reasons I first thought of but there are probably more.

What we really need to do is develop new antibiotics. This isn't really profitable, though, compared to how profitable other drugs can be, so pharmaceutical companies don't put much effort into it.

 

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