An antibiotic is a type of antimicrobial substance active against bacteria and is the most important type of antibacterial agent for fighting bacterial infections.
Antibiotic medications are widely used in the treatment and prevention of such infections. A limited number of antibacterial method also possess antiprotozoal activity. Sometimes the term antibiotic which means "opposing life", from New Latin based on ancient Greek roots is broadly used to refer to any substance used against microbesbut in the usual medical usage, antibiotics such as penicillin are those produced naturally by one microorganism fighting anotherwhereas nonantibiotic antibacterials such as sulfonamides and antiseptics are fully synthetic, antibacterial method.
However, both classes have the same goal of killing or preventing the growth of microorganisms, antibacterial method, and both are included in antimicrobial chemotherapy. Antibiotics revolutionized medicine in the 20th century.
Antibiotics are used to treat or prevent bacterial infections, antibacterial method,  and sometimes protozoan infections.
Metronidazole is effective against a number of parasitic diseases. When an infection is suspected of being responsible for an illness but the responsible pathogen has not been identified, antibacterial method, an empiric therapy is adopted. When the responsible pathogenic microorganism is already known or has been identified, definitive therapy can be started. This will usually involve the use of a narrow-spectrum antibiotic. The choice of antibiotic given will also be based on its cost.
Identification is critically important as it can reduce the cost and toxicity of the antibiotic therapy and also reduce the possibility of the emergence of antimicrobial resistance, antibacterial method. Antibiotics may be given as a preventive measure and this is usually limited to at-risk populations such as those with a weakened immune system particularly in HIV cases to prevent pneumoniathose taking immunosuppressive drugscancer patients, and those having surgery.
They antibacterial method an important role in dental antibiotic prophylaxis where their use may prevent bacteremia and consequent infective endocarditis. Antibiotics are also used to prevent infection in cases of neutropenia particularly cancer-related. There are many different routes of administration for antibiotic treatment. Antibiotics are usually taken by mouth.
In more severe cases, particularly deep-seated systemic infectionsantibiotics can be antibacterial method intravenously or by injection. Topical use is also one of the treatment options for some skin conditions including acne and cellulitis, antibacterial method.
Some systemic absorption of the antibiotic may occur; the quantity of antibiotic applied is difficult to accurately dose, and there is also antibacterial method possibility of local hypersensitivity reactions or contact dermatitis occurring, antibacterial method.
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. Common side-effects include diarrheaantibacterial method, resulting from disruption of the species composition in the intestinal floraresulting, for example, in overgrowth of pathogenic bacteria, such as Clostridium difficile, antibacterial method.
Exposure to antibiotics early in life is associated with increased body mass in humans and mouse models. Although there is a correlation between antibiotic use in early life and obesity, the effect of antibiotics on obesity in humans needs to be weighed against the beneficial effects of clinically indicated treatment with antibiotics in infancy, antibacterial method. There are few well controlled studies on whether antibiotic use increases the risk of oral contraceptive failure.
Gastrointestinal disorders or interpatient variability in oral contraceptive absorption affecting ethinylestradiol serum levels in the blood. If patient-specific risk factors antibacterial method reduced oral contraceptive efficacy are antibacterial method, backup contraception is recommended.
Interactions between alcohol and certain antibiotics may occur and may cause side-effects and decreased effectiveness of antibiotic therapy. Antibiotics such as metronidazoleantibacterial method, tinidazolecephamandolelatamoxefcefoperazone antibacterial method, cefmenoximeand furazolidonecause a disulfiram -like chemical reaction with alcohol by inhibiting its breakdown by acetaldehyde dehydrogenasewhich may result in vomiting, antibacterial method, nausea, and shortness of breath.
The successful outcome of antimicrobial therapy with antibacterial compounds depends on several factors, antibacterial method.
These include host defense mechanismsthe location of infection, and the pharmacokinetic and pharmacodynamic properties of the antibacterial. In important infectious diseases, including tuberculosis, combination therapy i, antibacterial method. In acute bacterial infections, antibacterial method, antibiotics as part of combination therapy are prescribed for their synergistic effects to improve treatment outcome as the combined effect of both antibiotics is better than their individual effect.
However, this can vary depending on the species of bacteria. Antibiotics are commonly classified based on their mechanism of actionchemical structure anti cancer phytonutrient program, or spectrum of activity. Most target bacterial functions or growth processes. Protein synthesis inhibitors macrolideslincosamidesand tetracyclines are usually bacteriostatic with the exception of bactericidal aminoglycosides.
Following a year break in discovering new classes of antibacterial compounds, four new classes of antibiotics have been brought into clinical use in the late s and early s: With advances in medicinal chemistrymost modern antibacterials are semisynthetic modifications of various natural compounds.
Compounds that are still isolated from living organisms are the aminoglycosideswhereas other antibacterial method example, antibacterial method, the sulfonamidesthe quinolonesand the oxazolidinones —are produced solely by antibacterial method synthesis.
Since the first pioneering efforts of Howard Florey and Chain inthe importance of antibiotics, including antibacterials, antibacterial method, to medicine has led to intense research into producing antibacterials at large scales. Following screening of antibacterials against a wide range of bacteria, production of the active compounds antibacterial method carried out using fermentationantibacterial method in strongly aerobic conditions.
The emergence of resistance of bacteria to antibiotics is a common phenomenon. Antibacterial method of resistance often reflects evolutionary processes that take place during antibiotic therapy, antibacterial method. The antibiotic treatment may select for bacterial strains with physiologically or genetically enhanced capacity to survive high doses of antibiotics.
Under certain conditions, it may result in preferential growth of resistant bacteria, while growth of susceptible bacteria is inhibited by the drug. Resistance may take the form of biodegredation of pharmaceuticals, such as sulfamethazine-degrading soil bacteria introduced to sulfamethazine through medicated pig feces, antibacterial method. Horizontal transfer is more likely to happen in locations of frequent antibiotic use.
Antibacterial resistance may impose a biological cost, antibacterial method, thereby reducing fitness of resistant strains, which can limit the spread of antibacterial-resistant bacteria, for example, in the absence of antibacterial compounds. Additional mutations, however, antibacterial method, may compensate for this fitness cost and can aid the survival of these bacteria.
Paleontological data show that both antibiotics and antibiotic resistance are ancient compounds and mechanisms. Several molecular mechanisms of antibacterial resistance exist. Intrinsic antibacterial resistance may be part of the genetic makeup of bacterial strains, antibacterial method.
Acquired resistance results from a mutation in the bacterial chromosome or the acquisition of extra-chromosomal DNA. Antibacterial-resistant strains and species, sometimes referred to as antibacterial method, now contribute to the emergence of diseases that were for a while well controlled.
For example, antibacterial method, emergent bacterial strains causing tuberculosis that are resistant to previously effective antibacterial treatments pose many therapeutic challenges.
Every year, nearly half a million new cases of multidrug-resistant tuberculosis Antibacterial method are estimated to occur worldwide. Per The ICU Book "The first rule of antibiotics is try not to use them, and the second rule is try not to use too many of them. Self-prescribing of antibiotics is an example of misuse. Also, incorrect or suboptimal antibiotics are prescribed for certain bacterial infections. Other forms of misuse include failure to take the entire prescribed course of the antibiotic, incorrect dosage and administration, or failure to rest for sufficient recovery.
Inappropriate antibiotic treatment, antibacterial method, for example, is their prescription to treat viral infections such as the common cold. One study on respiratory tract antibacterial method found "physicians were more likely to prescribe antibiotics to patients who appeared to expect them".
Several organizations concerned with antimicrobial resistance are lobbying to eliminate the unnecessary use of antibiotics. The emergence of antibiotic resistance has prompted restrictions on their use in the UK in Swann reportand the Antibacterial method has banned the use of antibiotics as growth-promotional agents since Food and Drug Administration have advocated restricting the amount of antibiotic use in food animal production.
Two federal bills S, antibacterial method. Despite pledges by food companies and restaurants to reduce or eliminate meat that comes from animals treated with antibiotics, the purchase of antibiotics for use antibacterial method farm animals has been increasing every year.
There has been extensive use of antibiotics in animal husbandry. In the United States, antibacterial method, the question of emergence of antibiotic-resistant bacterial strains due to use of antibiotics in livestock was raised antibacterial method the US Food and Drug Administration FDA in Before the early 20th century, treatments for infections were based primarily on medicinal folklore, antibacterial method. Mixtures with antimicrobial properties that antibacterial method used in treatments of infections were described over years ago.
The use of antibiotics in modern medicine began with the discovery of synthetic antibiotics derived from dyes. Synthetic antibiotic chemotherapy as a science and development of antibacterials began in Germany with Paul Ehrlich in the late s. He then proposed the idea that it might be possible to create chemicals that would act as a selective drug that would bind to and kill bacteria without harming the human host, antibacterial method. After screening hundreds of dyes against various organisms, antibacterial method, antibacterial methodhe discovered a medicinally useful drug, strawberries and vitamin c oranges first synthetic antibacterial salvarsan    now called arsphenamine.
The vitamin a and sebum of antibacterial treatment began with the discoveries of arsenic-derived synthetic antibiotics by Alfred Bertheim and Ehrlich in While their early compounds were too toxic, Ehrlich and Sahachiro Hataa Japanese bacteriologist working with Erlich in the quest for a drug to treat uses cephalexin for skin and muscleachieved success with the th compound in their series of experiments.
In Ehrlich and Hata announced their discovery, which they called drug "", at the Congress for Internal Medicine at Wiesbaden. This drug is now known as arsphenamine, antibacterial method. InEhrlich received the Nobel Prize in Physiology or Medicine for his contributions to immunology. The first sulfonamide and the first systemically active antibacterial drug, Prontosilwas developed by a research team led by Gerhard Domagk in or at the Bayer Laboratories of the IG Farben conglomerate in Germany,    for which Domagk received the Nobel Prize in Physiology or Medicine.
Research was stimulated apace by its success, antibacterial method. The discovery and development of this sulfonamide drug opened the era of antibacterials. Observations about the growth of rheumatoid and arthritis microorganisms inhibiting the growth of other microorganisms have been reported since the late 19th century. These observations of antibiosis between microorganisms led to the discovery of natural antibacterials.
Louis Pasteur observed, "if antibacterial method could intervene in the antagonism observed between some bacteria, it would offer perhaps the greatest hopes for therapeutics". Inphysician Sir William Roberts noted that cultures of the mold Penicillium glaucum that is used in the making of some types of blue cheese did not display bacterial contamination.
In Vincenzo TiberioItalian physician, published a paper on the antibacterial power of some extracts of mold. In his thesis, Duchesne proposed that bacteria and molds engage in a perpetual battle for survival. Duchesne observed that E. He also observed that when he inoculated laboratory animals with lethal doses of antibacterial method bacilli together with Penicillium glaucumthe animals did not contract typhoid. InSir Alexander Fleming postulated the existence of penicillinantibacterial method, a molecule produced by certain molds that kills or stops the growth of certain kinds of bacteria.
Fleming was working on a culture of disease-causing bacteria when he noticed the spores of a green mold, antibacterial method, Penicillium chrysogenumin one of his culture plates.
He observed that the presence of the mold killed or prevented the growth of the bacteria. Fleming believed that its antibacterial properties could be exploited for chemotherapy.
He initially characterized some of its biological properties, and attempted to use a crude preparation to treat some infections, but he was unable to pursue its further development without the aid of trained chemists.