Among our study population, low SDCs of INH and, to a lesser extent, RMP, appear to be associated with reduced sputum culture conversion after 2 months of treatment.
I n low TB incidence countries such as Canada, TB disease remains concentrated in urban settings with outbreaks involving homeless and under-housed populations that continue to challenge TB control programs. While the incidence of TB in Canada declined to 4.7/100,000 in 2009, the burden of TB cases continues to be diagnosed among foreign-born (FB) individuals. 1 In Alberta, the rate of TB among the FB is 17.7/100,000, compared to the Canadian-born (CB) population at 1.7/100,000. 1 Other descriptions of homeless and under-housed populations in Canadian urban centres have reported that disease remains concentrated among CB-Aboriginal (CB-AB) populations, 2 though the rise in the proportion of FB cases among homeless populations has been noted. 3 Although cases of TB in the FB represent the majority of cases in Alberta, there had previously been little documented transmission to other FB or to CB individuals. 4 The objective of this study is to describe the transmission of TB from FB populations to CB populations through shelterbased locations in the inner city of Edmonton, Alberta. METHODS Study population Edmonton is a northern Canadian city with a population of 1,024,820; 18.5% of the population are immigrants. 5 The homeless population is estimated to be 3,079 and is concentrated in the inner city of Edmonton. 6 All cases of TB in the province are centrally reported to TB Services. Between May 2008 and December 2009, 103 cases of active TB were reported within Edmonton (mean annual rate for 2008 and 2009 was 7.9/100,000); 19 cases were linked to three locations (one apartment building and three homeless shelters) within a one-block area of the inner city. Demographic and clinical characteristics A retrospective review of these 19 cases was completed by extracting demographic, clinical, treatment and contact tracing data from iPHIS. All TB cases were culture-confirmed at the Provincial Laboratory for Public Health (Edmonton, Alberta). Contacts were identified through social networking interviews and through resident lists of shared communal-living locations. Contact investigation was limited to chest x-ray (CXR), sputum for acid-fast bacilli (AFB) analysis and symptom inquiry.
Consistent with this goal, the Canadian Tuberculosis Committee of the Public Health Agency of Canada set a target Canadian TB incidence rate of 3.6 per 100,000 persons (one-half the incidence rate in Canada in 1990) for 2015. 2 So far, the achievement of this goal has been hampered by sustained high rates of TB in Aboriginal peoples and the foreign-born. Strategies aimed at eliminating TB focus on interrupting transmission and preventing TB in persons already infected. 2 This study is focused on the Canadian-born and describes in detail and places into context a complex cluster (chain of transmission) of TB cases in Alberta. Further, it uses the exercise to inform TB elimination strategy. A cluster of TB cases is one whose causative isolates of Mycobacterium tuberculosis share a common DNA fingerprint, suggesting a transmission link between them. 3 In instances where housing is unstable and patients may not know the names and locations of contacts, studies that incorporate DNA fingerprinting of isolates have provided insight into spatial and temporal patterns of transmission as well as factors that might contribute to rapid progression of disease. 4-8 In addition to DNA fingerprint data, contact tracing, mobility and socioeconomic data were used to further describe the chain of transmission and interpret its implications for TB elimination. METHODS This study was performed in Alberta, a province of Western Canada having a population of 2.94 million in 2001 (Statistics Canada) and where the majority of First Nations (66%) are living on-reserve (Indian and Northern Affairs Canada, 2001). In Alberta, initial isolates of M. tuberculosis are DNA fingerprinted in the Provincial Laboratory for Public Health using restriction fragment-length polymorphism (RFLP) supplemented by spoligotyping as necessary. 9,10 Over the 17-year period 1991-2007, all large clustersdefined as those having 15 or more case-patients-were identified and described according to the age, sex, population group
Linezolid is a potentially effective drug for the treatment of patients with drug-resistant tuberculosis. Among 13 patients treated for tuberculosis with linezolid in the present study, nine had treatment success and four remain on treatment. Adverse effects occurred in 11 (85%) patients, of whom three discontinued treatment because of adverse effects. The present study adds to the growing evidence supporting the efficacy of linezolid for tuberculosis, although treatment remains complicated by adverse effects.
We describe correlates of reduced antituberculous serum drug concentrations (SDCs) in HIV-infected patients receiving treatment for active tuberculosis (TB). Cross-sectional analysis of individuals diagnosed with HIV and active TB in Northern Alberta, Canada, was performed. Of the 30 HIV-TB cases, 27 underwent measurement of SDCs. Rates of low SDCs were 9 of 26 (34%) for isoniazid (INH) and 16 of 25 (64%) for rifamycins. Increased weight and elevated body mass index (BMI) correlated with low SDCs for rifampin (P < .05) and increased weight also correlated with reduced SDCs for INH (P < .05). This suggests that conventional antituberculous dosing may be too low and consideration should be given to increase the maximum initial weight-based doses in HIV-infected patients.
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