Antitubercular drugs are specific for mycobacteria. At usual doses, ethambutol and isoniazid are tuberculostatic, meaning that they inhibit the growth of M. tuberculosis. In contrast, rifampin is tuberculocidal, meaning that it destroys the mycobacteria. Because bacterial resistance to isoniazid and rifampin can develop rapidly, they should always be used with other antitubercular drugs.
The exact mechanism of action of ethambutol remains unclear, but it may be related to inhibition of cell metabolism, arrest of multiplication, and cell death. Ethambutol acts only against replicating bacteria.
乙胺丁醇的确切作用机理尚不明确。它可能跟细胞代谢、复制终止及细胞死亡有关，只对繁殖期细胞有效。
Breaking down walls 破坏细胞壁
Although isoniazid’s exact mechanism of action isn’t known, the drug is believed to inhibit the synthesis of mycolic acids, important components of the mycobacterium cell wall. This inhibition disrupts the cell wall. Only replicating, not resting, bacteria appear to be inhibited.
Rifampin inhibits RNA synthesis in susceptible organisms. The drug is effective primarily in replicating bacteria, but may have some effect on resting bacteria as well.
利福平抑制可疑生物的RNA合成。该药主要对繁殖期细菌有效，对静止期细菌也有些效果。
Acid based 呈酸性
The exact mechanism of action of pyrazinamide isn’t known, but the antimycobacterial activity appears to be linked to the drug’s conversion to the active metabolite pyrazinoic acid. Pyrazinoic acid, in turn, creates an acidic environment where mycobacteria can’t replicate.
Isoniazid usually is used with ethambutol, rifampin, or pyrazinamide. This is because combination therapy for TB and other mycobacterial infections can prevent or delay the development of resistance.
Ethambutol is used with isoniazid and rifampin to treat the patient with uncomplicated pulmonary TB. It’s also used to treat infections resulting from M. bovis and most strains of M. kansasii.
Although isoniazid is the most important drug for treating TB, bacterial resistance develops rapidly if it’s used alone. However, resistance doesn’t pose a problem when isoniazid is used alone to prevent TB in the patient who has been exposed to the disease, and no evidence exists of cross-resistance between isoniazid and other antitubercular drugs. Isoniazid is typically given orally, but may be given intravenously, if necessary.
Rifampin is a first-line drug for treating pulmonary TB with other antitubercular drugs. It combats many gram-positive and some gram-negative bacteria, but is seldom used for nonmycobacterial infections because bacterial resistance develops rapidly. It’s used to treat asymptomatic carriers of Neisseria meningitidis when the risk of meningitis is high, but it isn’t used to treat N. meningitidis infections because of the potential for bacterial resistance.
利福平是与其他抗结核病药物联用治疗肺结核的一线药物，可战胜很革兰氏阳性及一些革兰氏阴性细胞，但它很少用于治疗非分枝杆菌感染，这是由于细菌抗药性发展较快的缘故。该药还用于治疗无症状但脑膜炎风险较高的脑膜炎奈瑟球菌携带者，但不用于治疗脑膜炎奈瑟球菌感染，原因也是潜在的细菌抗药性。 On the TB front 结核病治疗
Pyrazinamide is currently recommended as a first-line TB drug in combination with ethambutol, rifampin, and isoniazid. Pyrazinamide is a highly specific drug that’s active only against M. tuberculosis. Resistance to pyrazinamide may develop rapidly when it’s used alone.
tuberculostatic – n. a. 抑制结核菌生长的（药）
tuberculocidal – a. n. 杀结核菌的（药）
antireplication station – 抗复制/繁殖配置
mycolic acids – 分枝菌酸
pyrazinoic acid – 吡嗪酸 N. meningitidis infections -- 脑膜炎奈瑟球菌感染
Test 1.A client with a positive skin test for TB isn’t showing signs of active disease. To help prevent the development of active TB, the client should be treated with isoniazid, 300 mg daily, for how long?
A. 10 to 14 days
B. 2 to 4 weeks
C. 3 to 6 months
D. 9 to 12 months
2.Which of the following family members exposed to TB would be at highest risk for contracting the disease?
A. 45-year-old mother
B. 17-year-old daughter
C. 8-year-old son
D. 76-year-old grandmother
Because of the increased incidence of resistant strains of TB, the disease must be treated for up to 24 months in some cases, but treatment typically lasts for 9-12 months. Isoniazid is the most common medication used for the treatment of TB, but other antibiotics are added to the regimen to obtain the best results.
2.D.76-year-old grandmother
Elderly persons are believed to be at higher risk for contracting TB because of decreased immunocompetence. Other high-risk populations in the US include the urban poor, AIDS, and minority groups.
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