Multidrug Resistant Tuberculosis

The incidence of multidrug-resistant tuberculosis (MDR TB) peaked during the resurgence of tuberculosis. The majority of cases involved those coinfected with HIV and was associated with a high mortality rate. With the increased surveillance of high-risk groups, the incidence of drug resistance has stabilized. 3 MDR TB continues to be a concern, however, especially to health care workers assigned to patients with resistant strains. Mycobacterium tuberculosis becomes resistant by spontaneous genetic mutation, often as a result of inadequate drug therapy or noncompliance with initial treatment. 29 The most powerful predictor of drug resistance remains a history of previous tuberculosis.9

The vast majority of MDR TB outbreaks have been in the HIV population. Clinically, the most common pattern is resistance to isoniazid and rifampin. 4 Available data suggest no difference in isoniazid resistance among those patients with or without HIV. Rifampin monoresistant tuberculosis has become a problem, especially in those with AIDS.10 Cases with rifampin monoresistance were more commonly seen in patients who had previously had tuberculosis, a history of diarrhea, rifabutin use, or antifungal therapy.10

For those HIV-negative patients who acquire MDR TB strains, or who are noncompliant with therapy, the course is less well defined. A study prior to the HIV epidemic reported a long-term response rate of 56 percent and a mortality rate of 22 percent.11 The patient population in this study had tuberculosis for a long period and were heavily pretreated for the disease by the community physician prior to referral. A more recent study from New York demonstrated a more promising course. 12 MDR TB was diagnosed more quickly (mean, 44 days) and, therefore, appropriate treatment started earlier. There were 25 HIV-negative patients in this group: eight were health care workers, and eight had a previous tuberculosis history. Overall, 96 percent had a good clinical response, with 64 percent completing a full course of therapy without relapse.12

Treatment of MDR TB remains challenging and depends on the sensitivity patterns from culture. The majority of regimens include four to six drugs with treatment as long as 18 to 24 months after sputum conversion. The fluoroquinolones have been used successfully in treatment of MDR TB. 912 Side effects of multiple-drug regimens are a common problem. When drug therapy fails, resectional surgery is considered to eradicate the disease.

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