I guess bacteria antibiotic resistance is a product of the modern world we now live in. But there is one thing I don’t understand about this phenomenon: Penicillin. Penicillin is a natural antibiotic derived from the natural fungus, penicillium. Penicillium has presumably been using its penicillin by-product for thousands, if not millions of years, I’m sure. Why does it just become eventually useless against bacteria when humans use it? How does the Penicillium deal with this phenomenon, and if it does have a way, why can’t humans just take a lesson from penicillium?
My guess would be that over time the natural version changes, so as to keep up with bacteria’s evolution of resistance. We can’t do that as easily, because randomly changing the formula is a good way to either kill the patient or render the result worthless; evolution works fine with that kind of approach, but doctors and patients tend to dislike cures that kill on a regular basis.
As well, we’ve often been using it wrong. Either on viral diseases that it can’t effect, or on people who might be sick and aren’t, or with people who take it until they feel better then stop, letting the bacteria survive and breed. And we gather the sick together in hospitals, which let’s resistant diseases spread resistance-genes more easily.
My WAG: Human use has exposed many more types and number of bacteria to the penicillium toxin than ever before.
Also, the resistance we are talking about specifically refers to bugs that cause disease in humans. I imagine there are lots of bugs that are naturally resistant to penicillium (when they have the right biology to be effected by penicillium in the first place). But we don’t care that they are resistant because they don’t cause disease in us.
Pretty much what Pullet said. Back before the use of penicillin as an antibiotic, there wasn’t much chance for the tuberculosis bacteria, for instance, to come into contact with the penicillum mold. It certainly didn’t happen enough for penicillin restant strains to evolve.
I think the major cause is the large evolutionary pressure caused by the massive human use of antibiotics. Especially the selection for the most resistant strains by people who discontinue treatment before they kill all the bacteria in their system. The fungi never applied such a magnitude of genetic pressure.
It is worth noting that bacteria evolve in a different way than us eukaryotes. They have much larger mutation rates, and they can pass on their genes not just to their progeny, but also to other bacteria in their environment through transformation and transjugation. And that’s another major reason that we cant just try to randomly change the formulaes to try and hit something that works. This is what the bacteria excell at. It would be like choosing the rapier as a weapon when challenging d’Artagnan to a duel.
Wide-scale resistance, sure. But the arms race between bacteria and things that want to kill them has been going on forever. There were naturally resistant strains before humans ever figured it out.
I have been to many 3rd-World nations, where local doctors prescribe antibiotics for everything-including colds! This use of antibiotics must also be a factor, in the emergence of resistant strains.My question: could we genetically engineer harmless disease strains, and introduced these into the environment? Then the harmless strains could crowd out the deadly ones…and we would have a situation where deadly germs would be replaced by harmless ones.
I’m a microbiology instructor, here is my opinion.
I’d say it’s more of a length of exposure/dose issue. The fungus kills those bacterium nearby, but as a species does it really affect the bacteria that much? There’s no selective pressure for them to develop a major resistance to penicillin, and those that do (via the sharing of plasmids that encode b-lactamase) only have to work that much harder to keep this resistance around in the absence of the fungus.
Fungi aren’t exactly taking over every corner of the world, and it’s probably not something the bacteria have to worry about too much. So, those that do not keep the resistant gene around will out-compete those bacteria that must invest energy into copying plasmids and expressing extra proteins. The doubling time of the non-resistant bacteria will be much faster in the absence of this specific fungus, allowing them to reproduce more than resistant strains.
Now, take humans. We expose bacteria to penicillin, and occasionally one obtains or develops a resistance. In the wild - big deal, that single fungus doesn’t kill that bacterium, but in reality neither species as a whole will be greatly affected. But on the other hand, in the human body, if just one survives (due to lack of finishing prescriptions, usually), that one will now be resistant to penicillin, as will all of its offspring. This resistant strain can now out-compete those bacteria that are not resistant to penicillin in this nutrient-rich environment. And the selective pressure is kept on that bacterium to keep the resistance genes around as antibiotics are continuously being introduced into the patient. Now an entire crop of bacteria has just become resistant in a patient, who can spread it to the next person.
Bonus fact: over 2/3rds of our antibiotics are actually produced by a bacterium of the genus Streptomyces, not a fungus. It naturally lives in the soil and uses these to out-compete over species.
In theory, yes, and there’s work being done in that direction. Although the idea generally is to introduce the harmless versions into humans, not the environment in general.
Interestingly, there’s a theory I’ve heard that we’ve already, inadvertantly done what you propose ( sort of ). The idea is that because of modern sanitation and germ theory, it’s much harder for obvious infectious diseases to spread. Not impossible, obviously, but not as easy as when people drank unsafe feces ( or worse ) contaminated water and thought that prayer was a protection against infection instead of washing your hands. As the theory goes, this creates selective pressure favoring diseases that are more mild, less visible; you won’t avoid kissing your girlfriend if she doesn’t seem to be infected with something.
I think there’s always been that pressure, though. It’s why there’s a worldwide AIDS epidemic and not a worldwide Ebola epidemic. Ebola is too fast acting and immediately cripling to perpetuate itself, while somebody can have HIV for years before developing AIDS.
But consider diseases that can spread by contaminated water, for example. Modern sanitation means they can’t spread by public water. And modern knowledge of germs means that we take care when dealing with someone who has diarrhea, vomiting, etc. We wash clothes and bedding and hands, and so on. Before modern sanitation, diseases could spread by contaminated water even if everyone avoided the obviosly sick person, and the people who actually tried to care for them didn’t know to take even simple precautions. So diseases that used that particular vector could be very obvious and lethal, without hurting their chances of success. They didn’t suffer from the pressure you speak of.
Now, diseases that spread by water ( for example ), at least in more developed countries, have to be more subtle. They can’t spread via the public water, which pretty much means they need personal contact, which means if they make people seriously ill, they likely won’t spread at all. Now, they ARE subjected to evolutionary pressure against dramatic symptoms. Which means that over the decades the more obvious and lethal strains are being outcompeted by the mild versions that you may not even notice.
