Background: Since the first years of antituberculosis chemotherapy, there has been controversy regarding the transmissibility, infectiousness, virulence and pathogenicity of susceptible and drug-resistant strains of Mycobacterium tuberculosis. Objective: To determine the incidence of active tuberculosis (TB) among individuals cohabiting with patients infected with susceptible and multidrug-resistant tuberculosis (MDR-TB). Methods: A case-control study was conducted. Cases of MDR-TB were defined as those infected with M. tuberculosis strains resistant to at least rifampin and isoniazid. Susceptible TB cases (controls) were defined as those first treated at approximately the same time as the first treatment of the MDR-TB cases - and cured by the time of the interview. Study cases were selected on the basis of the results of susceptibility tests, using the proportion method, carried out at the Central Laboratory of Public Health of the State of Ceará. The control group consisted of patients enrolled in the Tuberculosis Control Program between 1990 and 1999. Results: We evaluated 126 patients and 176 controls. The number of individuals sharing the household with patients was 557 in the MDR-TB group and 752 in the controls. The average number of exposed individuals per index case was 4.42 and 4.27 among patients and controls, respectively. Of the 557 MDR-TB-exposed individuals, 4.49% (25)received antituberculosis treatment after the respective index case had begun treatment, compared to 5.45% (41/752) among the controls ( p = 0.4468). Microepidemics of MDRTB were confirmed in eight families. Conclusion: Our results suggest that the incidence of active TB is comparable between households inhabited by MDRTB patients and those inhabited by susceptible-TB patients.

Keywords: Tuberculosis, multidrug-resistant/epidemiology. Tuberculosis/trasmission.

Background: Multidrug resistant tuberculosis is a threat to tuberculosis control worldwide. In many studies, it has been suggested that inadequate treatment is a risk factor for the development of multidrug resistent tuberculosis. Objective: To identify the factors associated with inadequate treatment in a group of patients with multidrug resistent tuberculosis. Method: The authors identified all drug sensitivity test for tuberculosis performed at the Central Laboratory of the state of Ceará from 1990 to 1999. Retrospective and prospective analysis was performed, comparing the characteristics of adequately treated patients with those of inadequately treated patients. Multidrug resistance was defined as resistance to 2 drugs (rifampin and isoniazid) or more, using the Cox proportional hazards model. Results: Of the 1,500 sensitivity test performed at the Central Laboratory of Public Health of the state of Ceará, 266 revealed multidrug-resistant strains. Of those 266 patients, the authors were able to identify only 153, of whom 19 were excluded. Thus, our sampling consisted of 134 patients. Univariate analysis demonstrated that the significant factors associated with inadequate treatment were: noncompliance with the treatment, extreme poverty, drug intolerance, mistakes in the management of the patients, lack of medication being supplied by the health service, two or more previous treatments, pronounced lung cavities and bilateral lesions on chest X-rays. They found a further association (p < 0.0010) between alcoholism or smoking and noncompliance with the treatment. In the multivariate analysis, the factors associated with an outcome of inadequate treatment were: two or more previous treatments (p < 0.0001, OR = 5.9; CI 95%: 2.5-13.7), pronounced cavitation (p < 0.0217, OR = 2.7; CI 95%: 1.2-6.1) and bilateral chest X-ray lesions (p < 0.0226, OR = 3.2; CI 95%: 1.4-7.4) Conclusion: In the study, the authors observed that factors related to inadequate treatment are wide-ranging. An attempt at better control of the disease is warranted, especially in those patients with pronounced cavitation or bilateral lesions in chest X-rays. And those with 2 or more previous treatments.

Keywords: Tuberculosis, multidrug-resistant. Risk factors.