📚 Antibiotic Resistance in Bacteria | 细菌的抗生素耐药性
Antibiotics revolutionised medicine in the 20th century, saving millions of lives by treating bacterial infections that were once fatal. Today, however, a growing crisis threatens to undo this progress: antibiotic resistance. Bacteria are evolving rapidly to survive the drugs designed to kill them, making common infections harder to treat and increasing the risk of disease spread, severe illness and death. Understanding how resistance develops and what we can do to slow it down is a core topic in IGCSE Edexcel Biology, linking natural selection to real-world public health.
抗生素在 20 世纪彻底改变了医学，挽救了无数生命，让曾经致命的细菌感染得以治愈。然而，如今一场日益严重的危机正威胁着这一成果：抗生素耐药性。细菌正在快速演化，以对抗那些旨在杀死它们的药物，这使得常见感染更难治疗，并增加了疾病传播、重症和死亡的风险。了解耐药性如何产生以及我们如何减缓其发展是 IGCSE Edexcel 生物学的核心课题，它将自然选择与现实世界的公共卫生联系起来。
1. What Are Antibiotics? | 什么是抗生素？
Antibiotics are chemical substances that kill bacteria or stop them from reproducing. They are produced naturally by fungi and bacteria in the environment, but many are now synthesised in laboratories. Antibiotics target structures and processes that are specific to bacterial cells, which is why they are generally harmless to human cells. Examples include penicillin, which attacks the bacterial cell wall, and tetracycline, which inhibits protein synthesis in bacteria.
抗生素是能够杀死细菌或阻止其繁殖的化学物质。它们由环境中的真菌和细菌自然产生，但现在许多是在实验室中合成的。抗生素靶向细菌细胞特有的结构和过程，因此它们通常对人体细胞无害。例如，青霉素攻击细菌细胞壁，而四环素抑制细菌中的蛋白质合成。
It is crucial to remember that antibiotics are ineffective against viruses, such as those causing the common cold, flu and COVID-19. Misusing antibiotics for viral infections is one of the key drivers of resistance.
必须牢记，抗生素对病毒无效，例如引起普通感冒、流感和 COVID-19 的病毒。将抗生素滥用于病毒感染是导致耐药性产生的主要因素之一。
2. How Do Antibiotics Kill Bacteria? | 抗生素如何杀死细菌？
Antibiotics work by interfering with vital bacterial functions without harming human cells. Common mechanisms include preventing the formation of peptidoglycan cell walls, blocking essential enzymes for DNA replication, or binding to bacterial ribosomes to halt protein production. Because human cells lack cell walls and have structurally different ribosomes, these drugs are selectively toxic.
抗生素通过干扰细菌的重要功能来发挥作用，同时不伤害人体细胞。其常见机制包括阻止肽聚糖细胞壁的形成、阻断 DNA 复制所需的关键酶，或与细菌核糖体结合以停止蛋白质生产。由于人体细胞没有细胞壁，且核糖体结构不同，这些药物具有选择毒性。
An analogy often used is a lock and key: the antibiotic molecule fits precisely into a bacterial target, disabling it. When resistance evolves, the 'lock' changes shape, and the drug no longer fits.
一个常用的类比是锁与钥匙：抗生素分子精确地嵌入细菌靶点，使其失活。当耐药性演化时，“锁”的形状发生改变，药物便不再适配。
3. Genetic Variation in Bacterial Populations | 细菌种群的遗传变异
Bacteria reproduce asexually by binary fission, producing genetically identical clones. However, variation does arise through random mutations during DNA replication. A mutation is a change in the nucleotide sequence of an organism's DNA. Most mutations are neutral or harmful to the bacterium, but by chance, a mutation may give the bacterium the ability to survive exposure to an antibiotic.
细菌通过二分裂无性繁殖，产生遗传上完全相同的克隆。然而，在 DNA 复制过程中通过随机突变会产生变异。突变是生物体 DNA 中核苷酸序列的改变。大多数突变对细菌而言是中性或有害的，但偶然之下，某个突变可能赋予细菌在抗生素环境中存活的能力。
In addition, bacteria can acquire resistance genes from other bacteria through horizontal gene transfer – by taking up free DNA from their environment, by conjugation (direct cell-to-cell transfer of plasmids), or by transduction (virus-mediated transfer). This means resistance can spread rapidly within a population without waiting for new mutations.
此外，细菌还能通过水平基因转移从其他细菌获得耐药基因——通过从环境中摄取游离 DNA、通过接合（细胞间质粒的直接转移）或通过转导（病毒介导的转移）。这意味着耐药性可以在种群中迅速传播，而无需等待新的突变。
4. Natural Selection and Antibiotic Resistance | 自然选择与抗生素耐药性
Charles Darwin's theory of evolution by natural selection explains how antibiotic resistance becomes common. In a population of bacteria, there is variation. If a patient takes an antibiotic, most susceptible bacteria are killed. However, if any bacteria possess a mutation or plasmid that confers resistance, they survive.
查尔斯·达尔文的自然选择进化论解释了抗生素耐药性如何变得普遍。在一个细菌种群中，存在变异。如果患者服用抗生素，大多数敏感的细菌会被杀死。然而，如果某些细菌拥有能产生耐药性的突变或质粒，它们就会存活下来。
These resistant bacteria then face less competition for resources and can reproduce rapidly, passing their resistant alleles to daughter cells. Over time, the proportion of resistant bacteria in the population increases. This is natural selection in action: the environmental pressure (antibiotic) selects for individuals with the advantageous characteristic.
这些耐药细菌随后面临较少的资源竞争，并能迅速繁殖，将耐药等位基因传递给子细胞。随着时间的推移，种群中耐药细菌的比例增加。这就是自然选择的作用：环境压力（抗生素）选择了具有有利特征的个体。
5. Step-by-Step Evolution of Resistance | 耐药性演化的逐步过程
Understanding the stages helps clarify the concept:
理解各个阶段有助于厘清这个概念：
- Stage 1: Variation – Within a large bacterial population, random mutations produce a few bacteria with genes that give them reduced susceptibility to a specific antibiotic.
第一步：变异——在一个大的细菌种群中，随机突变产生少数细菌，其基因使它们对某种特定抗生素的敏感性降低。 - Stage 2: Selection pressure – When the antibiotic is introduced, it acts as a selective agent.
第二步：选择压力——当引入抗生素时，它充当选择剂。 - Stage 3: Survival of the fittest – Non-resistant bacteria die, but the resistant ones survive and continue to divide.
第三步：适者生存——非耐药细菌死亡，但耐药细菌存活并继续分裂。 - Stage 4: Increase in allele frequency – The resistance allele becomes much more common in subsequent generations. Eventually, the entire strain may become resistant to that drug.
第四步：等位基因频率增加——耐药等位基因在后续世代中变得更为常见。最终，整个菌株可能对该药物产生耐药性。
6. How Resistant Bacteria Spread | 耐药菌如何传播
Resistant bacteria do not only pass on resistance to their offspring; they can also spread from person to person through direct contact, contaminated surfaces, food, water and airborne droplets. In hospitals, poor hygiene practices can transmit these 'superbugs' between patients, especially those with weakened immune systems.
耐药细菌不仅将耐药性传递给后代，还能通过直接接触、受污染的表面、食物、水和飞沫在人与人之间传播。在医院里，不良的卫生操作可能将这些“超级细菌”传播给患者，尤其是那些免疫系统较弱的人。
Global travel and the overuse of antibiotics in agriculture contribute significantly to the worldwide spread of resistant strains. Bacteria know no borders, making antibiotic resistance a global health emergency.
全球旅行和农业中抗生素的过度使用极大地助长了耐药菌株在世界范围内的传播。细菌不分国界，这使得抗生素耐药性成为全球卫生紧急事件。
7. Consequences: Hard-to-Treat Infections | 后果：难以治疗的感染
When a bacterial strain becomes resistant to one or more antibiotics, common infections such as pneumonia, tuberculosis, gonorrhoea and urinary tract infections become much harder to treat. Patients may require longer hospital stays, more expensive second-line or third-line drugs with severe side effects, and face an increased risk of death.
当一种细菌菌株对一种或多种抗生素产生耐药性时，肺炎、结核病、淋病和尿路感染等常见感染就变得更加难以治疗。患者可能需要更长的住院时间，使用更昂贵且副作用严重的二线或三线药物，并面临更高的死亡风险。
Routine medical procedures such as surgeries, cancer chemotherapy and organ transplants also become more dangerous because they rely on effective antibiotics to prevent and treat subsequent infections.
常规医疗程序，如外科手术、癌症化疗和器官移植，也会变得更加危险，因为它们依赖有效的抗生素来预防和治疗随之而来的感染。
8. Examples: MRSA and Multidrug-Resistant TB | 实例：MRSA 与多重耐药结核病
MRSA (Methicillin-resistant Staphylococcus aureus) is a bacterium that has become resistant to several widely used penicillin-class antibiotics. It frequently causes skin infections, bloodstream infections and pneumonia, particularly in hospital settings. MRSA infections are difficult to treat and require careful antibiotic choice and strict isolation protocols.
MRSA（耐甲氧西林金黄色葡萄球菌）是一种已对若干广泛使用的青霉素类抗生素产生耐药性的细菌。它常引起皮肤感染、血流感染和肺炎，尤其是在医院环境中。MRSA 感染难以治疗，需要谨慎选择抗生素并执行严格的隔离方案。
Multidrug-resistant tuberculosis (MDR-TB) is caused by Mycobacterium tuberculosis that is resistant to at least isoniazid and rifampicin, the two most powerful first-line anti-TB drugs. MDR-TB requires extended treatment with less effective, more toxic drugs and has a much lower cure rate.
多重耐药结核病 (MDR-TB) 由至少对异烟肼和利福平这两种最强大的一线抗结核药物产生耐药性的结核分枝杆菌引起。MDR-TB 需要使用疗效较差、毒性更大的药物进行延长治疗，且治愈率低得多。
| Characteristic 特点 | Susceptible TB 敏感结核病 | MDR-TB 多重耐药结核病 |
|---|---|---|
| Effective standard drugs 有效标准药物 | Isoniazid, rifampicin 异烟肼、利福平 | Resistant to both 对两者均耐药 |
| Treatment duration 治疗时长 | ~6 months 约6个月 | Up to 2 years 长达2年 |
| Cure rate 治愈率 | >95% if completed 完成则>95% | ~50% 约50% |
9. Practical Measures to Reduce Antibiotic Resistance | 减少抗生素耐药性的实际措施
Slowing the development of antibiotic resistance requires coordinated action at individual, healthcare and government levels. Everyone can contribute:
减缓抗生素耐药性的发展需要个人、医疗和政府层面的协调行动。每个人都能作出贡献：
- Only take antibiotics when prescribed by a medical professional for a confirmed or strongly suspected bacterial infection.
仅在医疗专业人员针对确诊或高度疑似的细菌感染开具处方时使用抗生素。 - Never demand antibiotics for viral illnesses such as colds and flu.
切勿因感冒和流感等病毒性疾病而要求使用抗生素。 - Practise good hygiene – regular hand washing, proper wound care, and safe food handling reduce the need for antibiotics in the first place.
保持良好的卫生习惯——勤洗手、妥善处理伤口和安全处理食物，能从源头上减少对抗生素的需求。 - Maintain up-to-date vaccinations to prevent bacterial infections.
按期接种疫苗以预防细菌感染。
10. The Importance of Completing Antibiotic Courses | 完成抗生素疗程的重要性
Patients often stop taking antibiotics when they begin to feel better, but this dangerous practice encourages resistance. A course of antibiotics is designed to last long enough to kill all the disease-causing bacteria. If treatment is stopped early, some bacteria may survive – particularly those that are partially resistant – and they can multiply, causing a relapse that is harder to treat.
患者常常在开始感觉好转时停止服用抗生素，但这种危险的做法会助长耐药性。抗生素疗程的设计时长足以杀死所有致病细菌。如果治疗提前终止，一些细菌——尤其是那些部分耐药的细菌——可能存活下来并繁殖，导致更难治疗的复发。
Doctors provide specific instructions: 'Finish the course, even if you feel better.' The goal is to eliminate the entire population of infecting bacteria, leaving none behind to develop full resistance.
医生会给出明确指示：“完成整个疗程，即使您感觉好转。” 目标是清除所有感染细菌种群，不让任何细菌留下以发展为完全耐药。
11. Antibiotic Stewardship in Healthcare | 医疗中的抗生素管理
Hospitals and healthcare authorities implement antibiotic stewardship programmes to optimise the use of antibiotics. These include prescribing the right drug at the right dose for the right duration, using narrow-spectrum antibiotics whenever possible, and relying on culture and sensitivity testing to identify the most effective treatment.
医院和卫生当局实施抗生素管理计划，以优化抗生素的使用。这包括在正确的时间使用正确的药物、正确的剂量和正确的疗程，尽可能使用窄谱抗生素，并依赖细菌培养和药敏测试来确定最有效的治疗方法。
Surveillance systems track resistance patterns globally, allowing public health organisations to issue warnings and update treatment guidelines. Education of both clinicians and the public is a continuous process that stresses that antibiotics are precious, finite resources.
监测系统在全球范围内追踪耐药模式，使公共卫生组织能够发布警告并更新治疗指南。对临床医生和公众的教育是一个持续的过程，它强调抗生素是宝贵而有限的资源。
12. Conclusion: A Shared Responsibility | 结论：共同的责任
Antibiotic resistance is a textbook example of evolution by natural selection observable within a human lifetime. It originates from genetic variation through mutation and horizontal gene transfer, and is driven by the selective pressure exerted by antibiotic use. Without effective antibiotics, modern medicine would crumble. Combating this threat demands that we understand the mechanisms, adhere to prescribed treatments, and favour prevention over misuse. Every dose of antibiotics saved today is a life that can still be saved tomorrow.
抗生素耐药性是自然选择进化的一个教科书范例，可在人类一生中直接观察得到。它源于通过突变和水平基因转移产生的遗传变异，并受到抗生素使用所带来的选择压力的驱动。没有有效的抗生素，现代医学将坍塌。应对这一威胁要求我们理解其机制，遵守处方治疗，并以预防代替滥用。今天每节省一剂抗生素，明天就仍能挽救一条生命。
Published by TutorHao | Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图