Evolution of antibiotic resistance in bacteria
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Antibiotics and antifungals save lives, but their use can contribute to the development of resistant germs. Antimicrobial resistance is accelerated when the presence of antibiotics and antifungals pressure bacteria and fungi to adapt. Show Antibiotics and antifungals kill some germs that cause infections, but they also kill helpful germs that protect our body from infection. The antimicrobial-resistant germs survive and multiply. These surviving germs have resistance traits in their DNA that can spread to other germs. Spread of Germs & Resistance MechanismsTo survive, germs can develop defense strategies against antibiotics and antifungals called resistance mechanisms. DNA tells the germ how to make specific proteins, which determine the germ’s resistance mechanisms. Bacteria and fungi can carry genes for many types of resistance. When already hard-to-treat germs have the right combination of resistance mechanisms, it can make all antibiotics or antifungals ineffective, resulting in untreatable infections. Alarmingly, antimicrobial-resistant germs can share their resistance mechanisms with other germs that have not been exposed to antibiotics or antifungals. This table gives a few examples of defense strategies used to resist the effects of antibiotics or antifungals. Mutations can result in antibiotic resistance in bacteria. Resistant bacteria survive antibiotic treatment and can increase in numbers by natural selection. MutationsBacteria grow and multiply fast and can reach large numbers. When bacteria multiply, one cell divides into two cells. Before the bacterium can divide, it needs to make two identical copies of the DNA in its chromosome; one for each cell. Every time the bacterium goes through this process there is a chance (or risk, depending on the end result) that errors occur; so-called mutations. These mutations are random and can be located anywhere in the DNA. Mutations can also form due to external factors like radiation or harmful chemicals. Natural selectionWhile some mutations are harmful to the bacteria, others can provide an advantage given the right circumstances. Here, Darwin’s theory of natural selection comes in. If a mutation gives the bacterium an advantage in a particular environment, this bacterium will grow better than its neighbors and can increase in numbers – it is selected for. Mutations can provide resistance to antibioticsMutations are one way for bacteria to become resistant to antibiotics. Some spontaneous mutations (or genes that have been acquired from other bacteria through horizontal gene transfer) may make the bacterium resistant to an antibiotic (See: Resistance mechanisms for information about how bacteria resist antibiotic action). If we were to treat the bacterial population with that specific antibiotic, only the resistant bacteria will be able to multiply; the antibiotic selects for them. These bacteria can now increase in numbers and the end result is a population of mainly resistant bacteria.  It is important to understand that selection of antibiotic resistant bacteria can occur anywhere an antibiotic is present at a selective concentration. When we treat an infection, selection can occur at any site in the body to which the antibiotic reaches. Thus, the antibiotic can select for resistance genes and mechanisms in both pathogenic bacteria and in commensal bacteria living in the body that have nothing to do with the infection in question. By using narrow-spectrum antibiotics (when possible), the risk of selecting for antibiotic resistance in the commensal flora decreases. Short video that explains natural selection of antibiotic resistanceSelected ResourcesResourceDescriptionEmergence and spread of antibiotic-resistant bacteriaVideo. Narrated presentation from ReAct that describes how bacteria develop resistance and how bacteria can spread.A cinematic approach to drug resistanceVideo that visualizes the development and spread of antibiotic resistant bacteria in real time, using a giant petri dish with different concentrations of antibiotics. With explanatory article.The rise in antibiotic resistanceAnimation of selection of resistant bacteria in the body, some resistance mechanisms and how they may spread.What causes antibiotic resistance?Video. This animated TED-Ed video gives an overview of how antibiotics function, how bacteria evolve to resist their action and how selection of resistant bacteria works (5 min). Also available in Spanish.Antibiotic Resistance ExplainedVideo that explains selection and spread of antibiotic resistance in an easy to understand manner.Natural Selection and the Rock Pocket MouseVideo from HHMI BioInteractive about a real-life example of natural selection (11 min).Mutations – selection: the bacteria resistVideo about natural selection of antibiotic resistant bacteria (5 min). Also embedded in text above. How does antibiotic resistance evolve in bacteria?Antimicrobial resistance is accelerated when the presence of antibiotics and antifungals pressure bacteria and fungi to adapt. Antibiotics and antifungals kill some germs that cause infections, but they also kill helpful germs that protect our body from infection. The antimicrobial-resistant germs survive and multiply.
What is the history of resistance to bacteria?Resistance was first recorded in the bacterial species of streptococci and gonococci. Resistance first presented a major issue to antibiotic use with the treatment of tuberculosis (TB). Currently, antibiotic resistance remains a major public health threat and a contributor to antimicrobial resistance worldwide.
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