Infection and disease among household contacts of patients with multidrug-resistant tuberculosis

SETTING: Urban public teaching and referral hospital in Espirito Santo, Bra zil. OBJECTIVE: To assess whether rates of infection and progression to active t uberculosis (TB) differed between household contacts of patients with multi drug-resistant (MDR) and drug susceptible (DS) pulmonary tuberculosis. DESIGN: Household contacts were assessed for evidence of TB infection and d isease by purified protein derivative (PPD) skin testing, physical examinat ion, chest X-ray, and sputum smear and culture. RESULTS: Among 133 close contacts of patients with MDR-TB, 44% were PPD-pos itive (greater than or equal to 10 mm) compared to 37% of 231 contacts of t he DS-TB cases (P = 0.18, chi (2) test, or 1.2, 95%CI 0.8-2). In a multivar iate logistic regression analysis, after allowance for between-household va riation in PPD responses, PPD positivity among household contacts of patien ts with MDR-TB remained comparable to PPD positivity in contacts of patient s with DS-TB (OR 2.1, 95%CI 0.7-6.5). Respectively six (4%) and 11 (4%) con tacts of the MDR- and DS-TB cases were found to have active TB at the time of initial evaluation or during follow-up (P = 0.78, chi (2) test). Five of six contacts of MDR-TB cases and nine of nine contacts of DS-TB cases who developed TB, and for whom drug susceptibility test results were available, had the same bacterial susceptibility profiles as their index cases. DNA f ingerprinting analysis of Mycobacterium tuberculosis isolates was identical between household contacts with active TB and the index MDR or DS-TB case for all 14 pairs compared. CONCLUSION: Our data suggest that the prevalence of tuberculous infection a nd progression to active TB among household contacts exposed to DS and MDR- TB cases is comparable, despite a longer duration of exposure of contacts t o the index case in patients with MDR-TB.