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Background: In spring 1993, four students in a high school were diagnosed with tuberculosis resistant to isoniazid, streptomycin, and ethionamide. Methods: To investigate potential transmission of drug-resistant tuberculosis, a retrospective cohort study with case investigation and screening by tuberculin skin tests and symptom checks was conducted in a high school of approximately 1400 students. Current and graduated high-school students were included in the investigation. DNA fingerprinting of available isolates was performed. Results: Eighteen students with active tuberculosis were identified, Through epidemiologic and laboratory investigation, 13 cases were linked; 8 entered 12th grade in fall 1993; 9 of 13 had positive cultures for Mycobacterium tuberculosis with isoniazid, streptomycin, and ethionamide resistance, and all 8 available isolates had identical DNA fingerprints. No staff member had tuberculosis. One student remained infectious for 29 months, from January 1991 to June 1993, and was the source case for the outbreak. Another student was infectious for 5 months before diagnosis in May 1993 and was a treatment failure in February 1994 with development of rifampin and ethambutol resistance in addition to isoniazid, streptomycin, and ethionamide. In the fall 1993 screening, 292 of 1263 (23%) students tested had a positive tuberculin skin test. Risk of infection was highest among 12th graders and classroom contacts of the two students with prolonged infectiousness. An additional 94 of 928 (10%) students tested in spring 1994 had a positive tuberculin skin test; 22 were classroom contacts of the student with treatment failure and 21 of these had documented tuberculin skin test conversions. Conclusion: Extensive transmission of drug-resistant tuberculosis was documented in this high school, along with missed opportunities for prevention and control of this outbreak. Prompt identification of tuberculosis cases and timely interventions should help reduce this public health problem. (J Pediatr 1997;131:863-8)

Objective: To investigate possible transmission of multidrug-resistant tuberculosis (MDR-TB) in a dental setting. Design: A retrospective, descriptive study of dental workers (DWs), patients, and practice characteristics. Patients: Two dental workers (DW1 and DW2) with acquired immunodeficiency syndrome and MDR-TB. Setting: A hospital-based (Hospital X) human immunodeficiency virus (HIV) dental clinic in New York City. Methods: To identify dental patients with tuberculosis (TB), patients treated in the dental clinic at Hospital X during 1990 were cross-matched with those listed in the New York City Department of Health Tuberculosis Registry Mycobacterium tuberculosis isolates from both DWs and from dental patients with TB were tested for antimicrobial susceptibility and typed by restriction fragment length polymorphism (RFLP) analysis. Infection control practices were reviewed. Results: M tuberculosis isolates infecting DW1 and DW2 were resistant to isoniazid and rifampin and had identical RFLP patterns. DW1 and DW2 worked in close proximity to each other in a small HIV dental clinic in Hospital X during 1990. Of 472 patients treated in the dental clinic in 1990, 41 (8.7%) had culture-proven M tuberculosis infection. Of these 41, 5 had isolates with resistance patterns similar to both DWs; however, for four available isolates, the RFLP patterns were different from the patterns of the DWs. Sixteen of the 41 patients received dental treatment while potentially infectious. Dental patients were not routinely questioned about TB by dental staff, nor were all dental staff screened routinely for TB. No supplemental environmental measures for TB were employed in the dental clinic in 1990. Conclusions: Our investigation suggests that MDR-TB transmission may have occurred between two DWs in an HIV dental clinic. Opportunities for transmission of TB among dental staff and patients were identified. TB surveillance programs for DWs and appropriate infection control strategies, including worker education, are needed to monitor and minimize exposure to TB in dental settings providing care to patients at risk for TB.