Antibiotic resistance is becoming common among organisms that cause a variety of human diseases. All of the following strategies help reduce the risk of antibiotic resistance evolving in a susceptible bacterial population except                  . a. using antibiotics only when appropriate, for bacterial infections that are not clearing up naturally; b. using the drugs as directed, taking all the antibiotic over the course of days prescribed; c. using more than one antibiotic at a time for difficult-to-treat organisms; d. preventing natural selection by reducing the amount of evolution the organisms can perform; e. reducing the use of antibiotics in non–health-care settings, such as agriculture

Video transcript

Hi everyone. Let's look at our next question. It says antibiotic resistance. A classic example of directional selection is exacerbated by the and our choices. Our overuse of antibiotics, limited use of antibiotics. Non use of antibiotics or restricted use of antibiotics. So let's think about what directional selection is. We can recall from our content video that it's when the average being a type of a population shifts in one direction over time usually favoring an extreme genotype. So you've got different phenotype is caused by different genes. But some sort of pressure causes the average phenotype of the population to shift toward the extreme. And antibiotic resistance is an example of this because you have population of bacteria that in general are vulnerable to antibiotics. And over time we see this um the phenotype of this population shift towards antibiotic resistance. More and more bacteria become resistant to an antibiotic. So let's think about what kind of use of antibiotics would cause this selection pressure. And the answer is the more that the bacteria exposed antibiotics. So if we have um more usage of antibiotics that leads to more bacteria being exposed. Well then what happens is we see that the vulnerable bacteria are eliminated. They're killed by the antibiotics. But the resistance bacteria survive and proliferate. So lots of usage of antibiotic. We see more as we saw here the average phenotype of the population as more and more vulnerable bacteria are eliminated by heavy antibiotic usage. We have more and more strained more and more the surviving bacteria are resistant to the antibiotics. So over time the entire population of bacteria that survives um shifts towards antibiotic resistance. So as we see, we're talking about more usage of antibiotics. So when we look at our choices choice, a overuse of antibiotics is what we want here. When we look at our remaining choices, we have B is limited use of antibiotics. C. Is non use and D. Is restricted use of antibiotics. All those choices involve using fewer antibiotics, so they are not correct because we're talking about a situation where the bacteria exposed to more antibiotics. So antibiotic resistance exacerbated made worse by the a overuse of antibiotics. See you in the next video.