|
Drug resistance is the reduction in effectiveness of a drug such as an antimicrobial, anthelmintic or an antineoplastic in curing a disease or condition. When the drug is not intended to kill or inhibit a pathogen, then the term is equivalent to ''dosage failure'' or drug tolerance. More commonly, the term is used in the context of resistance that pathogens have "acquired", that is, resistance has evolved. Antimicrobial resistance and antineoplastic resistance challenge clinical care and drive research. When an organism is resistant to more than one drug, it is said to be multidrug-resistant. Even the immune system of an organism is in essence a drug delivery system, albeit endogenous, and faces the same arms race problems as external drug delivery. The development of antibiotic resistance in particular stems from the drugs targeting only specific bacterial molecules (almost always proteins). Because the drug ''is'' so specific, any mutation in these molecules will interfere with or negate its destructive effect, resulting in antibiotic resistance.〔(【引用サイトリンク】title=Antibiotic Resistance and Evolution )〕 Bacteria are capable of not only altering the enzyme targeted by antibiotics, but also by the use of enzymes to modify the antibiotic itself and thus neutralise it. Examples of target-altering pathogens are ''Staphylococcus aureus'', vancomycin-resistant enterococci and macrolide-resistant ''Streptococcus'', while examples of antibiotic-modifying microbes are ''Pseudomonas aeruginosa'' and aminoglycoside-resistant ''Acinetobacter baumannii''. In short, the lack of concerted effort by governments and the pharmaceutical industry, together with the innate capacity of microbes to develop resistance at a rate that outpaces development of new drugs, suggests that existing strategies for developing viable, long-term anti-microbial therapies are ultimately doomed to failure. Without alternative strategies, the acquisition of drug resistance by pathogenic microorganisms looms as possibly one of the most significant public health threats facing humanity in the 21st century.〔(【引用サイトリンク】title=Reading: The Resistance Phenomenon in Microbes and Infectious Disease Vectors: Implications for Human Health and Strategies for Containment -- Workshop Summary - The National Academies Press )〕 Resistance to chemicals is only one aspect of the problem, another being resistance to physical factors such as temperature, pressure, sound, radiation and magnetism, and not discussed in this article, but found at Physical factors affecting microbial life. ==Introduction== Drug, toxin, or chemical resistance is a consequence of evolution and is a response to pressures imposed on any living organism. Individual organisms vary in their sensitivity to the drug used and some with greater fitness may be capable of surviving drug treatment. Drug-resistant traits are accordingly inherited by subsequent offspring, resulting in a population that is more drug-resistant. Unless the drug used makes sexual reproduction or cell-division or horizontal gene transfer impossible in the entire target population, resistance to the drug will inevitably follow. This can be seen in cancerous tumors where some cells may develop resistance to the drugs used in chemotherapy.〔(【引用サイトリンク】title=Tolerance and Resistance to Drugs )〕 Chemotherapy causes fibroblasts near tumors to produce large amounts of the protein WNT16B. This protein stimulates the growth of cancer cells which are drug-resistant.〔("Chemo 'Undermines Itself' Through Rogue Response" ),''BBC News'', 5 August 2012.〕 Malaria in 2012 has become a resurgent threat in South East Asia and sub-Saharan Africa, and drug-resistant strains of ''Plasmodium falciparum'' are posing massive problems for health authorities.〔(【引用サイトリンク】title=Resistance spread 'compromising' fight against malaria )〕 Leprosy has shown an increasing resistance to dapsone. A rapid process of sharing resistance exists among single-celled organisms, and is termed horizontal gene transfer in which there is a direct exchange of genes, particularly in the biofilm state. A similar asexual method is used by fungi and is called "parasexuality". Examples of drug-resistant strains are to be found in microorganisms〔(【引用サイトリンク】title=Mechanisms of drug action and resistance )〕 such as bacteria and viruses, parasites both endo- and ecto-, plants, fungi, arthropods,〔http://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_5/b_fdi_12-13/15697.pdf〕 mammals, birds, reptiles,〔(【引用サイトリンク】title=Reptiles Magazine, your source for reptile and herp care, breeding, and enthusiast articles )〕 fish, and amphibians.〔 In the domestic environment, drug-resistant strains of organism may arise from seemingly safe activities such as the use of bleach,〔(【引用サイトリンク】title=How household bleach works to kill bacteria )〕 tooth-brushing and mouthwashing,〔http://www.healthstores.com/dentists/new_dental_products.htm〕 the use of antibiotics, disinfectants and detergents, shampoos, and soaps, particularly antibacterial soaps,〔(【引用サイトリンク】title=Should antibacterial soap be outlawed? )〕 hand-washing, surface sprays, application of deodorants, sunblocks and any cosmetic or health-care product, insecticides, and dips. The chemicals contained in these preparations, besides harming beneficial organisms, may intentionally or inadvertently target organisms that have the potential to develop resistance.〔http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Antibacterial_cleaning_products〕 "Drug resistance develops naturally, but careless practices in drug supply and use are hastening it unnecessarily." (- Center for Global Development ) "The overuse of antibacterial cleaning products in the home may be producing strains of multi-antibiotic-resistant bacteria." - (Better Health Channel - Australian Government ) "The use and misuse of antimicrobials in human medicine and animal husbandry over the past 70 years has led to a relentless rise in the number and types of microorganisms resistant to these medicines - leading to death, increased suffering and disability, and higher healthcare costs." - (World Health Organisation 2010 ) "Deaths from acute respiratory infections, diarrhoeal diseases, measles, AIDS, malaria, and tuberculosis account for more than 85% of the mortality from infection worldwide. Resistance to first-line drugs in most of the pathogens causing these diseases ranges from zero to almost 100%. In some instances resistance to second- and thirdline agents is seriously compromising treatment outcome. Added to this is the significant global burden of resistant, hospital-acquired infections, the emerging problems of antiviral resistance and the increasing problems of drug resistance in the neglected parasitic diseases of poor and marginalized populations." - (WHO Global Strategy for Containment of Antimicrobial Resistance 2010 ) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「drug resistance」の詳細全文を読む スポンサード リンク
|