An antibiotic is a type of antimicrobial [抗微生物的] substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of such infections. They may either kill or inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal [抗原生动物的] activity. Antibiotics are not effective against viruses such as the common cold or influenza; drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics.
Sometimes, the term antibiotic—literally "opposing life", from the Greek roots "against" and "life"—is broadly used to refer to any substance used against microbes, but in the usual medical usage, antibiotics (such as penicillin) are those produced naturally (by one microorganism fighting another), whereas nonantibiotic antibacterials (such as sulfonamides [磺胺类] and antiseptics) are fully synthetic. Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction [腐烂]. Sepsis is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is followed by suppression of the immune system. Sepsis is also called blood poisoning.
Antibiotics have been used since ancient times. Many civilizations used topical application of mouldy bread, with many references to its beneficial effects arising from ancient Egypt, Nubia [努比亚], China, Serbia [塞尔维亚], Greece, and Rome. The first person to directly document the use of molds to treat infections was John Parkinson (1567–1650). Antibiotics revolutionized medicine in the 20th century. Alexander Fleming (1881–1955) discovered modern day penicillin in 1928, the widespread use of which proved significantly beneficial during wartime. However, the effectiveness and easy access to antibiotics have also led to their overuse and some bacteria have evolved resistance to them. The World Health Organization has classified antimicrobial resistance as a widespread "serious threat [that] is no longer a prediction for the future, it is happening right now in every region of the world and has the potential to affect anyone, of any age, in any country".
There are many different routes of administration for antibiotic treatment. Antibiotics are usually taken by mouth. In more severe cases, particularly deep-seated systemic infections, antibiotics can be given intravenously [through or into a vein] or by injection. A deep-seated attitude, feeling, or idea is strong and is very difficult to change. Where the site of infection is easily accessed, antibiotics may be given topically in the form of eye drops onto the conjunctiva for conjunctivitis [结膜炎] or ear drops for ear infections and acute cases of swimmer's ear. 在水温较高的泳池和温泉中，绿脓杆菌能感染人的耳部和皮肤，导致游泳性耳炎和毛囊炎的发生。
Antibiotics are screened for any negative effects before their approval for clinical use, and are usually considered safe and well tolerated. However, some antibiotics have been associated with a wide extent of adverse side effects ranging from mild to very severe depending on the type of antibiotic used, the microbes targeted, and the individual patient. Taking probiotics [益生菌] during the course of antibiotic treatment can help prevent antibiotic-associated diarrhea.
Exposure to antibiotics early in life is associated with increased body mass in humans and mouse models.
Interactions between alcohol and certain antibiotics may occur and may cause side effects and decreased effectiveness of antibiotic therapy. While moderate alcohol consumption is unlikely to interfere with many common antibiotics, there are specific types of antibiotics, with which alcohol consumption may cause serious side effects. 很多头孢类药物在体内和酒精产生双硫仑样作用，会产生很严重的毒副作用。
Antibiotics are commonly classified based on their mechanism of action, chemical structure, or spectrum of activity. Most target bacterial functions or growth processes. Those that target the bacterial cell wall (penicillins and cephalosporins [先锋霉素]) or the cell membrane, or interfere with essential bacterial enzymes have bactericidal activities. Protein synthesis inhibitors are usually bacteriostatic [抑菌剂]. "Narrow-spectrum" antibiotics target specific types of bacteria, such as gram[革兰氏]-negative or gram-positive, whereas broad-spectrum antibiotics affect a wide range of bacteria. 在21世纪末和21世纪初，四种新的抗生素被引入临床使用：环脂肽(如达托霉素)、甘氨酰环素(如替加环素)、恶唑烷酮(如利奈唑啉)和脂酰霉素(如非达沙霉素)。百度翻译处理这样的句子还是很强很方便滴。
Anti- is used to form adjectives and nouns that describe sb/sth that is opposed to a particular system, practice, or group of people. Anti- is also used to describe things that are intended to destroy sth harmful or to prevent sth from happening. antibody:抗体。
六级/考研单词: antibiotic, bacteria, infect, medicare, inhibit, virus, influenza, literal, usage, synthesis, tissue, injure, suppress, immune, poison, mold, evolve, heal, classify, affection, administer, inject, acute, tolerate, adverse, mild, decrease, therapy, moderate, interfere, spectrum, indispensable