No abstract

In this outbreak of tuberculosis, the growth characteristics of the strain involved greatly exceeded those of other clinical isolates of M. tuberculosis. The extensive transmission of tuberculosis may have been due to the increased virulence of the strain rather than to environmental factors or patient characteristics.

The transmission of Mycobacterium tuberculosis that we describe aboard a commercial aircraft involved a highly infectious passenger, a long flight, and close proximity of contacts to the index patient.

Epidemiologic relatedness of Mycobacterium tuberculosis isolates from Arkansas residents diagnosed with tuberculosis in 1992-1993 was assessed using IS6110- and pTBN12-based restriction fragment length polymorphism (RFLP) and epidemiologic investigation. Patients with isolates having similar IS6110 patterns had medical records reviewed and were interviewed to identify epidemiologic links. Complete RFLP analyses were obtained for isolates of 235 patients; 78 (33%) matched the pattern of > or = 1 other isolate, forming 24 clusters. Epidemiologic connections were found for 33 (42%) of 78 patients in 11 clusters. Transmission of M. tuberculosis likely occurred many years in the past for 5 patients in 2 clusters. Of clusters based only on IS6110 analyses, those with > or = 6 IS6110 copies had both a significantly greater proportion of isolates that matched by pTBN12 analysis and patients with epidemiologic connections, indicating IS6110 patterns with few bands lack strain specificity. Secondary RFLP analysis increased specificity, but most clustered patients still did not appear to be epidemiologically related. RFLP clustering in rural areas may not represent recent transmission.

Improvement is needed in the complex, multistep process of contact investigations to ensure that contacts of patients with active pulmonary TB are identified and appropriately screened.

Three epidemiologically linked multidrug-resistant (MDR) tuberculosis (TB) outbreaks in 1990-1991 involving New York State (NYS) inmates suggested MDR-TB was widespread in NYS prisons. Inmate lists were linked to 1990-1992 TB registries, medical records were reviewed, and movement histories for inmates with MDR-TB were examined within and between prisons and hospitals. In 1990-1991, 171 inmates were diagnosed with TB. This rate (156.2/100,000) was significantly higher than the 1990-1991 US rate (10.4/100,000) and the 1986 rate among NYS inmates (105.5/100,000). Of 171 cases, 155 were cultured-confirmed; 37 (32%) of 116 with drug susceptibilities determined had MDR-TB. Two other inmates with TB before 1990 were diagnosed with MDR-TB in 1990-1991. Of 39 inmates with MDR-TB, 38 (97%) were infected with the human immunodeficiency virus and 34 (87%) have died. These 39 lived in 23 of the 68 NYS prisons while potentially infectious; 12 were transferred through 20 prisons while ill with MDR-TB. Policies of correctional systems on infection control and inmate transfers need to be reevaluated to prevent spread of TB.

Drug-susceptible and drug-resistant isolates of Mycobacterium tuberculosis were recovered from 2 patients, 1 with isoniazid-resistant tuberculosis (patient 1) and another with multidrug-resistant tuberculosis (patient 2). An investigation included patient interviews, record reviews, and genotyping of isolates. Both patients worked in a medical-waste processing plant. Transmission from waste was responsible for at least the multidrug-resistant infection. We found no evidence that specimens were switched or that cross-contamination of cultures occurred. For patient 1, susceptible and isoniazid-resistant isolates, collected 15 days apart, had 21 and 19 restriction fragments containing IS6110, 18 of which were common to both. For patient 2, a single isolate contained both drug-susceptible and multidrug-resistant colonies, demonstrating 10 and 11 different restriction fragments, respectively. These observations indicate that simultaneous infections with multiple strains of M. tuberculosis occur in immunocompetent hosts and may be responsible for conflicting drug-susceptibility results, though the circumstances of infections in these cases may have been unusual.

This investigation showed that a young child can transmit Mycobacterium tuberculosis to a large number of contacts. Children with tuberculosis, especially cavitary or laryngeal tuberculosis, should be considered potentially infectious, and screening of their contacts for infection with M. tuberculosis or active tuberculosis may be required.