EFFICACY OF CONTROL MEASURES IN PREVENTING NOSOCOMIAL TRANSMISSION OF MULTIDRUG-RESISTANT TUBERCULOSIS TO PATIENTS AND HEALTH-CARE WORKERS

Objective: To assess the efficacy of control measures in decreasing nosocomial transmission of multidrug-resistant tuberculosis. Design: Retrospective cohort study. Setting: A teaching hospital in New York City. Population: 40 patients hospitalized with multidrug-resistant tuberculosis (case-patients) and health care workers receiving tuberculin skin testing. Interventions: Centers for Disease Control and Prevention (CDC) 1990 guidelines for preventing transmission of tuberculosis, including 1) prompt isolation and treatment of patients with tuberculosis; 2) rapid diagnostic techniques for processing Mycobacterium tuberculosis specimens; 3) negative-pressure isolation rooms; and 4) molded surgical masks for health care workers. Measurements: Proportion of case-patients with nosocomially acquired tuberculosis and rate of tuberculin skin test conversion among health care workers before and after implementation of control measures. Results: The proportion of patients with multidrug-resistant strains of M. tuberculosis decreased after the interventions (10 of 70 [14%] compared with 30 of 95 [32%] patients before the intervention; relative risk [RR], 0.5; 95% CI, 0.2 to 0.9). Before onset of multidrug-resistant tuberculosis, case-patients in the intervention period were as likely to be hospitalized on high-risk wards containing patients with tuberculosis (4 of 10 compared with 17 of 30 patients; RR, 0.7; P = 0.5) but were less likely to be exposed to another case-patient with tuberculosis (1 of 10 compared with 20 of 30 patients; RR, 0.2; P = 0.003). Tuberculin skin test conversion rates for health care workers assigned to wards housing patients with tuberculosis were lower in the intervention period than in the preintervention period (4 of 78 [5%] compared with 15 of 90 [17%] conversions; P = 0.02), decreasing to levels observed for workers assigned to other wards (4 of 78 [5%] compared with 9 of 228 [4%] conversions; P = 0.7). Conclusions: Implementing control measures reduced nosocomial transmission of multidrug-resistant strains to patients and health care workers.