Transmission of Mycobacterium tuberculosis from medical waste

Context Washington State has a relatively low incidence rate of tuberculosi s (TB) infection. However, from May to September 1997, 3 cases of pulmonary TB were reported among medical waste treatment workers at 1 facility in Wa shington. There is no previous documentation of Mycobacterium tuberculosis transmission as a result of processing medical waste. Objective To identify the source(s) of these 3 TB infections. Design, Setting, and Participants Interviews of the 3 infected patient-work ers and their contacts, review of patient-worker medical records and the st ate TB registry, and collection of all multidrug-resistant TB (MDR-TB) isol ates identified after January 1, 1995, from the facility's catchment area; DNA fingerprinting of all isolates; polymerase chain reaction and automated DNA sequencing to determine genetic mutations associated with drug resista nce; and occupational safety and environmental evaluations of the facility. Main Outcome Measures Previous exposures of patient-workers to TB; verifica tion of patient-worker tuberculin skin test histories; identification of ot her cases of TB in the community and at the facility; drug susceptibility o f patient-worker isolates; and potential for worker exposure to live M tube rculosis cultures. Results All 3 patient-workers were younger than 55 years, were born in the United States, and reported no known exposures to TB. We did not identify o ther TB cases. The 3 patient-workers' isolates had different DNA fingerprin ts. One of 10 MDR-TB catchment-area isolates matched an MDR-TB patient-work er isolate by DNA fingerprint pattern, DNA sequencing demonstrated the same rare mutation in these isolates. There was no evidence of personal contact between these 2 individuals. The laboratory that initially processed the m atching isolate sent contaminated waste to the treatment facility. The faci lity accepted contaminated medical waste where it was shredded, blown, comp acted, and finally deactivated. Equipment failures, insufficient employee t raining, and respiratory protective equipment inadequacies were identified at the facility. Conclusion Processing contaminated medical waste resulted in transmission o f M tuberculosis to at least 1 medical waste treatment facility worker.