A train passenger with pulmonary tuberculosis: evidence of limited transmission during travel.
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In January 1996, smear- and culture-positive tuberculosis (TB) was diagnosed for a 22-year-old black man after he had traveled on two U.S. passenger trains (29.1 hours) and a bus (5.5 hours) over 2 days. To determine if transmission had occurred, passengers and crew were notified of the potential exposure and instructed to undergo a tuberculin skin test (TST). Of the 240 persons who completed screening, 4 (2%) had a documented TST conversion (increase in induration of > or = 10 mm between successive TSTs), 11 (5%) had a single positive TST (> or = 10 mm), and 225 (94%) had a negative TST (< 10 mm). For two persons who underwent conversion, no other risk factors for a conversion were identified other than exposure to the ill passenger during train and/or bus travel. These findings support limited transmission of Mycobacterium tuberculosis from a potentially highly infectious passenger to other persons during extended train and bus travel. (+info)
Observations on animal and human health during the outbreak of Mycobacterium bovis in game farm wapiti in Alberta.
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This report describes and discusses the history, clinical, pathologic, epidemiologic, and human health aspects of an outbreak of Mycobacterium bovis infection in domestic wapiti in Alberta between 1990 and 1993, shortly after legislative changes allowing game farming. The extent and seriousness of the outbreak of M. bovis in wapiti in Alberta was not fully known at its onset. The clinical findings in the first recognized infected wapiti are presented and the postmortem records for the herd in which the animal resided are summarized. Epidemiologic findings from the subsequent field investigation are reviewed, the results of recognition and investigation of human exposure are updated, and recommendations for reduction of human exposure are presented. (+info)
Differential avian and human tuberculin skin testing in non-tuberculous mycobacterial infection.
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OBJECTIVE: To determine the sensitivity of differential avian and human delayed-type hypersensitivity skin testing in the diagnosis of non-tuberculous mycobacterial lymphadenitis. METHOD: Retrospective review of all patients with culture proved non-tuberculous mycobacterial lymph node infections who also had differential avian and human skin testing performed over a 10 year period from 1986 to 1996. RESULTS: One hundred and twenty four patients had non-tuberculous mycobacteria isolated from lymph nodes over this period, 59 of whom had differential skin testing performed. The sensitivity of a response of >/= 10 mm to the avian precipitin was 58 of 59. No patient had both a negative human and avian Mantoux. The sensitivity of the human Mantoux alone for diagnosing non-tuberculous mycobacterial infection was 81% for a response of >/= 5 mm and 66% for >/= 10 mm. Ten patients had a 0 human response. Fifty five of the 59 patients had an avian response at least 2 mm greater than the human response. CONCLUSION: The avian Mantoux is a very sensitive method of diagnosing non-tuberculous mycobacterial infection in children. The human Mantoux is not sensitive enough to be used alone as a surrogate to diagnose non-tuberculous mycobacterial infection. (+info)
Prevalence of Mycobacterium tuberculosis infection among injection drug users in Toronto.
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BACKGROUND: Injection drug users are at increased risk of Mycobacterium tuberculosis infection and active tuberculosis (TB). The primary objective of this study was to determine the prevalence of M. tuberculosis infection among injection drug users in Toronto, as indicated by a positive tuberculin skin test result. An additional objective was to identify predictors of a positive skin test result in this population. METHODS: A cross-sectional study was carried out involving self-selected injection drug users in the city of Toronto. A total of 171 participants were recruited through a downtown Toronto needle-exchange program from June 1 to Oct. 31, 1996. RESULTS: Of 167 subjects tested, 155 (92.8%) returned for interpretation of their skin test result within the designated timeframe (48 to 72 hours). Using a 5-mm cut-off, the prevalence rate of positive tuberculin skin test results was 31.0% (95% confidence interval 23.8% to 38.9%). Birth outside of Canada and increasing age were both predictive of a positive result. INTERPRETATION: There is a high burden of M. tuberculosis infection in this population of injection drug users. The compliance observed with returning for interpretation of skin test results indicates that successful TB screening is possible among injection drug users. (+info)
Comparison between a whole blood interferon-gamma release assay and tuberculin skin testing for the detection of tuberculosis infection among patients at risk for tuberculosis exposure.
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A new test that measures interferon-gamma (IFN-gamma) release in whole blood following stimulation with tuberculin has the potential to detect tuberculosis infection using a single blood draw. The IFN-gamma release assay was compared with the standard tuberculin skin test (TST) among 467 intravenous drug users at risk for tuberculosis in urban Baltimore. Among 300 human immunodeficiency virus (HIV)-seronegative patients, the IFN-gamma release assay was positive in 177 (59%), whereas the TST was positive in 71 (24%), for a percent agreement of 59% (kappa=26%). Among 167 HIV-seropositive subjects, the IFN-gamma release assay identified 32 reactors (19%); the TST identified 16 reactors (9.6%), for a percent agreement of 82% (kappa=28%). The IFN-gamma release assay detected more reactors than did the TST, but its agreement with TST was weak. As the TST is an imperfect standard, further evaluation of the IFN-gamma release assay among uninfected persons and persons with culture-confirmed tuberculosis will be useful. (+info)
Tuberculin skin testing among economically disadvantaged youth in a federally funded job training program.
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Low income, medically underserved communities are at increased risk for tuberculosis. Limited population-based national data are available about tuberculous infection in young people from such backgrounds. To determine the prevalence of a positive tuberculin skin test among economically disadvantaged youth in a federally funded job training program during 1995 and 1996, the authors evaluated data from medical records of 22,565 randomly selected students from over 100 job training centers throughout the United States. An estimated 5.6% of students had a documented positive skin test or history of active tuberculosis. Rates were highest among those who were racial/ethnic minorities, foreign born, and (among foreign-born students) older in age (p < 0.001). Weighted rates (adjusting for sampling) were 1.3% for white, 2.2% for Native American, 4.0% for black, 9.6% for Hispanic, and 40.7% for Asian/Pacific Islander students; rates were 2.4% for US-born and 32.7% for foreign-born students. Differences by geographic region of residence were not significant after adjusting for other demographic factors. Tuberculin screening of socioeconomically disadvantaged youth such as evaluated in this study provides important sentinel surveillance data concerning groups at risk for tuberculous infection and allows recommended public health interventions to be offered. (+info)
Immune responses induced in cattle by virulent and attenuated Mycobacterium bovis strains: correlation of delayed-type hypersensitivity with ability of strains to grow in macrophages.
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Comparison of immune responses induced in cattle by virulent and attenuated strains of Mycobacterium bovis will assist in identifying responses associated with resistance or susceptibility to disease. Four strains of M. bovis, one which is virulent in guinea pigs (WAg201) and three which are attenuated in guinea pigs (an isoniazid-resistant strain [WAg405], ATCC 35721, and BCG) were compared for their abilities to induce immune responses in cattle and to grow in bovine lung alveolar macrophage cultures. Extensive macroscopic lesions were found only in cattle inoculated with the virulent M. bovis strain. Strong antibody responses to M. bovis culture filtrate, as well as persistently high levels of gamma interferon and interleukin-2 released from purified protein derivative (PPD)-stimulated peripheral blood lymphocyte cultures, were observed in the cattle inoculated with the virulent strain compared to those inoculated with the attenuated strains. All cattle inoculated with the virulent strain or two of the attenuated strains (WAg405 and ATCC 35721) elicited strong delayed-type hypersensitivity responses to PPD in skin tests, while animals inoculated with BCG induced only a weak response. The three strains which produced strong skin test responses proliferated well in bovine alveolar macrophages and induced high levels of proinflammatory cytokine mRNAs compared to BCG. Our study showed that skin test responsiveness to PPD correlated with the ability of the strains to grow in alveolar macrophages rather than to their pathogenicity in cattle. (+info)
Safety and effectiveness of BCG vaccination in preterm babies.
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AIM: To assess the cell mediated immune response to BCG vaccine in preterm babies. METHODS: Sixty two consecutive preterm babies born at < 35 weeks of gestation were randomly allocated into two groups. Babies in group A were vaccinated early at 34-35 weeks and group B were vaccinated late at 38-40 weeks of postconceptional age. The two groups were similar in terms of: gestational age (mean (SD) 33.1 (1. 1) and 33 (1.2) weeks, respectively); birthweight 1583 (204) and 1546 (218) g; neonatal problems; socioeconomic status; and postnatal weight gain. The cell mediated immune response to BCG was assessed using the Mantoux test and the lymphocyte migration inhibition test (LMIT) 6-8 weeks after BCG vaccination. Induration of >5 mm after the Mantoux test was taken as a positive response. RESULTS: There was no significant difference in the tuberculin conversion rates (80% and 80.7%, respectively), positive LMIT (86.6% and 90.3%, respectively), or BCG scar (90.0% and 87.1%, respectively) among the two groups. CONCLUSIONS: Prematurity seems to be an unlikely cause for poor vaccine uptake. Preterm babies can be effectively vaccinated with BCG at 34-35 weeks of postconceptional age, the normal time of discharge in a developing country. (+info)