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The question is based on an intuition that antibiotic resistance can't come along. This mutation will probably make bacteria less tenacious. Is there any research how AR bacteria compete with normal one in an antibiotic free environment? Because if them generally lose to normal bacteria then AR bacteria is not a big threat and they can't spread to much.

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They CAN spread like wild fire when an antibiotic is introduced in their environment. – biogirl Jan 9 '14 at 7:45
up vote 4 down vote accepted

The antibiotic resistance adds to growth cost. In an antibiotic free medium the antibiotic-susceptible strains will outgrow the resistant ones. See this

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So it is a myth that antibiotic resistant bacteria is somehow dangerous? You will not catch this AR infection if you are not using antibiotic. Normal bacteria will outgrow it. – ZAB Jan 9 '14 at 11:22 Your immune system acts as a barrier to both strains (both are pathogenic)... Then you take antibiotics to control the infection. In this condition the resistant ones thrive. – WYSIWYG Jan 9 '14 at 12:44
AR bacteria is less viable it will not be present if I didn't use antibiotic. Both this infections fight not only with immune system but also with eachother and AR lose. – ZAB Jan 9 '14 at 12:48
We are talking about the condition in which the immune system requires drug supplementation. For example in the case of tuberculosis.. The drug resistant strains are a major issue of concern – WYSIWYG Jan 9 '14 at 12:54
I am interesting how AR strains are able to spread. If they can't compete with normal bacteria then worst possible scenario is to ban antibiotics worldwide for a year. Wait while AR bacteria instinct in a competition with normal one and remove the ban. Or better to switch between two types of antibiotics on odd and even years. If AR bacteria really lose to normal one then the issue is not as bad as it depicted in mass media. – ZAB Jan 9 '14 at 13:35

In short, yes. Perhaps the best way of thinking about antibiotic resistance is not to think of there being 'antibiotic resistance' genes at all, but rather ordinary alleles that are vertically transferred in the typical fashion until at a certain time a deleterious chemical agent is introduced and one specific allele just happens to mitigate the effects of that chemical. It is less a matter of competition than it is of blind chance. Now of course, in principle, the lucky genetic element that will ensure survival may come with an increased energy cost as opposed to the 'wild-type' genome expression, but considering the general mechanisms of antibiotic resistance, one or two extra gene products, maybe a slightly less active enzyme, an extra membrane transporter, the cost is typically not excessive. In culture, antibiotic-resistant bacterial strains grow essentially as fast as non-resistant strains.

Now concerning the retaining of the resistance after removal of the antibiotic, if the gene is integrated into the genome with the proper regulatory apparatus, it can remain in the species essentially forever. In the case of plasmids or other mobile genetic elements, bacteria do tend to lose these through random processes between divisions, however, many of these elements do have mechanisms to preserve (plasmid addiction) and propagate themselves (horizontal gene transfer).

The most important thing to remember about resistance, however, is that only an infinitesimally small proportion of the population actually needs the resistance genetic element to actually start a new resistant population upon antibiotic introduction.

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" In culture, antibiotic-resistant bacterial strains grow essentially as fast as non-resistant strains.".. Antibiotic resistance does pose and additional cost on growth.. It might be difficult to observe it in a gross scale.. However it is true that that resistant strains must have optimized the protein synthesis machinery as much as possible to minimize cost. – WYSIWYG Jan 9 '14 at 18:04

In general, antibiotic resistant strains may be a little less fit than sensitive strains in the absence of the antibiotic. But that doesn't mean they are at all times and places instantly competed out of existence. Once you apply the antibiotic, the resistant organisms grow from resistant organisms that were in the population to start with.

Ad of course once you have a large number of resistant organisms in the population, selection might encourage the increase in organisms bearing compensatory mutations, such that the growth of those organisms is closer to the growth level of sensitive organisms.

Your premise is a little weird. Resistant organisms are out there. XDR tuberculosis, MSRA Staph...why would you assert that those can't be problems when empirically, they obviously are?

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Totally agree with the last sentence. They ARE there and they ARE bad. – biogirl Jan 10 '14 at 16:56
How long will XDR tuberculosis and MSRA Staph last if we ban antibiotics or if we will globally alter one antibiotic with another once in a decade? That is a question. If resistant stains are less fit then normal stains then they will extinct. – ZAB Jan 29 '14 at 13:43
Ban all antibiotics all together? Do you understand that the idea is for people to not die from infectious diseases? Sitting back and watching someone die from a drug-sensitive strain because you are banned from using antibiotics is not an improvement over watching someone die because you don't have a useful antibiotic to use. – swbarnes2 Jan 29 '14 at 17:39
You do not listen. Ban penicillin worldwide and treat people with metronidazole. Then switch. Stain resistant to both of them will not survive in competition. After a year of penicillin treatment all metronidazole resistant stains will extinct. And so on. – ZAB Feb 5 '14 at 13:12
You can't treat everything with one antibiotic. For one thing, there are people who are allergic to penicililn. And I'm sorry, but there are such things as compensatory mutations, it certainly is possible for resistant organism to compete with sensitive ones. Just repeating over and over again that that's not true isn't helpful. – swbarnes2 Feb 5 '14 at 19:45

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