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posted by Fnord666 on Tuesday December 05 2017, @02:51PM   Printer-friendly
from the deja-vu-all-before-again dept.

We've been told its all our fault that antibiotic drugs are losing the arms race to bacteria. We tend to over use the drugs, and the bacteria tend to develop immunity.

However, a story in Ars Technica suggests we aren't just one step ahead, we may actually be a couple steps behind the bacteria:

Genetic analyses of 288 bacterial isolates collected between 1911 and 1969 from 31 countries show that Salmonella developed resistance to an antibiotic several years before that drug even hit the market. The finding suggests that the diarrhea-causing bacteria were somehow primed to withstand the semi-synthetic antibiotic ampicillin before doctors could prescribe it in the early 1960s. Thus, overuse in humans didn't drive the emergence of that resistance.

Instead, the authors speculate that overuse of a related antibiotic—penicillin G—in animals may be to blame.

[...] "Although our study cannot identify a causal link between the use of penicillin G and the emergence of transmissible ampicillin-resistance in livestock, our results suggest that the non-clinical use of penicillins like [penicillin G] may have encouraged the evolution of resistance genes in the late 1950s," Weill said in a press statement.


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  • (Score: 1, Insightful) by Anonymous Coward on Tuesday December 05 2017, @04:08PM (1 child)

    by Anonymous Coward on Tuesday December 05 2017, @04:08PM (#605681)

    Cross-resistance is a problem. When a resistance to an antibiotic evolves, it often works decently with many antibiotics. Typically one of the molecular pumps that eliminates undesired molecules has gotten mutated to get rid of molecules with a certain feature, that feature being what matters. Other times, the thing upon which the drug acts will have changed, and this stops many drugs from targeting that thing.

    Cross-border organisms are a problem. It does us no good to go all organic when Mexico and China and India are using antibiotics on farm animals with wild abandon. Organisms do not stay put.

    An environment with antibiotics will very rapidly select for resistance. An environment without antibiotics will select for non-resistance, due to the cost of having resistance, but normally this is very slow. Once we screw up, getting the world back to a better state is not easy or fast. The best we could do is to spray non-resistant stuff everywhere, but there are so many types of organisms and they even share resistance plasmids.

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  • (Score: 4, Insightful) by HiThere on Tuesday December 05 2017, @05:17PM

    by HiThere (866) Subscriber Badge on Tuesday December 05 2017, @05:17PM (#605714) Journal

    Everything you say is correct, but you still don't understand the real problem. People talk as if these are "new mutations", but generally they aren't. Antibiotics evolved as bacteria-on-bacteria weapons, and defenses against them evolved in lock-step. The thing is, they used to be low frequency alleles. They didn't provide that much benefit. Once they start providing a lot of benefit (say you kill off their competition) their frequency increases markedly. And it doesn't quickly go down when the selection pressure eases. The things aren't generally that expensive to run, they just didn't provide much advantage. (Yes, there are exceptions to this rule.) So you need to remove the stressor for long enough for random mutation to disable it in most of the population, the way eyes degrade in cave fish...it's a genetic drunkards walk with a low mutational frequency. (Well, bacteria mutate a lot more frequently than mammals do, but there's also a huge population of them, and they don't undergo meiosis, so genes don't just get lost in the shuffle.)

    Another contributory factor is that many bacteria freely share genes...even across species, and probably across phyla. It also happens with larger animals and plants, but a *lot* less frequently, and usually a virus needs to act as an intermediary. But this means that lots of these defenses are mobile between species of bacteria.

    Note: I'm not a biologist. If you want details, talk to someone else. But the facts they tell you will include the ones I mentioned.

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