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Multi-drug-resistant tuberculosis (MDR-TB) is defined as a form of TB infection caused by bacteria that are resistant to treatment with at least two of the most powerful first-line anti-TB drugs,〔(【引用サイトリンク】website=WHO MDR TB Factsheet )〕 isoniazid (INH) and rifampicin (RMP).〔 Five percent (5%) of all TB cases across the globe in 2013 were estimated to be MDR-TB cases, including 3.5% of newly diagnosed TB cases, and 20.5% of previously treated TB cases.〔 While rates of MDR-TB infections are relatively low in North America and Western Europe, they are an increasingly serious problem worldwide, in particular in areas of the Russian Federation, the former Soviet Union and other parts of Asia.〔(【引用サイトリンク】url=https://extranet.who.int/sree/Reports?op=vs&path=/WHO_HQ_Reports/G2/PROD/EXT/MDRTB_Indicators_map )〕 MDR-TB infection may be classified as either primary or acquired. Primary MDR-TB occurs in patients who have not previously been infected with TB but who become infected with a strain that is resistant to treatment. Acquired MDR-TB occurs in patients during treatment with a drug regimen that is not effective at killing the particular strain of TB with which they have been infected. Rates of primary MDR-TB are low in North America and Western Europe: in the US in 2000, the rate of primary MDR-TB was 1% of all cases of TB nationally.〔 Most cases of acquired MDR-TB are due to inappropriate treatment with a single anti-TB drug, usually INH. This can occur due to a medical provider, such as a doctor or nurse, improperly prescribing ineffective treatment, but may also be due to the patient not taking the medication correctly, which can be due to a variety of reasons, including expense or scarcity of medicines, patient forgetfulness, or patient stopping treatment early because they feel better. Treatment of MDR-TB requires treatment with second-line drugs, usually four or more anti-TB drugs for a minimum of 6 months, and possibly extending for 18–24 months if rifampin resistance has been identified in the specific strain of TB with which the patient has been infected.〔 In general, second-line drugs are less effective, more toxic and much more expensive than first-line drugs. Under ideal program conditions, MDR-TB cure rates can approach 70%.〔 ==Epidemiology== Cases of MDR tuberculosis have been reported in every country surveyed. MDR-TB most commonly develops in the course of TB treatment, and is most commonly due to doctors giving inappropriate treatment, or patients missing doses or failing to complete their treatment. Because MDR tuberculosis is an airborne pathogen, persons with active, pulmonary tuberculosis caused by a multidrug-resistant strain can transmit the disease if they are alive and coughing.〔 TB strains are often less fit and less transmissible, and outbreaks occur more readily in people with weakened immune systems (e.g., patients with HIV). Outbreaks among non immunocompromised healthy people do occur, but are less common.〔 As of 2013, 3.7% of new tuberculosis cases have MDR-TB. Levels are much higher in those previously treated for tuberculosis - about 20%. WHO estimates that there were about 0.5 million new MDR-TB cases in the world in 2011. About 60% of these cases occurred in Brazil, China, India, the Russian Federation and South Africa alone. In Moldova, the crumbling health system has led to the rise of MDR-TB. In 2013, the Mexico–United States border was noted to be "a very hot region for drug resistant TB", though the number of cases remained small. It has been known for many years that INH-resistant TB is less virulent in guinea pigs, and the epidemiological evidence is that MDR strains of TB do not dominate naturally. A study in Los Angeles, California found that only 6% of cases of MDR-TB were clustered. Likewise, the appearance of high rates of MDR-TB in New York City in the early 1990s was associated with the explosion of AIDS in that area. In New York City, a report issued by city health authorities states that fully 80 percent of all MDR-TB cases could be traced back to prisons and homeless shelters. When patients have MDR-TB, they require longer periods of treatment—about two years of multidrug regimen. Several of the less powerful second-line drugs, which are required to treat MDR-TB, are also more toxic, with side effects such as nausea, abdominal pain, and even psychosis. The Partners in Health team had treated patients in Peru who were sick with strains that were resistant to ten and even twelve drugs. Most such patients require adjuvant surgery for any hope of a cure. 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「Multi-drug-resistant tuberculosis」の詳細全文を読む スポンサード リンク
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