Predictors of clustering of tuberculosis in Greater Vancouver: a molecular epidemiologic study.
BACKGROUND
The understanding of how tuberculosis is transmitted can be improved by combining DNA fingerprinting of Mycobacterium tuberculosis with conventional epidemiologic methods. We used such techniques to determine the predictors of clustering of identical isolates from tuberculosis patients in Vancouver.


METHODS
We used the restriction fragment length polymorphism (RFLP) technique and, if necessary, spoligotyping to determine DNA patterns of M. tuberculosis isolates from all patients with newly diagnosed tuberculosis in Greater Vancouver reported to the Division of Tuberculosis Control from January 1995 to March 1999. Isolates were considered to be part of a cluster if they had an identical DNA pattern. We also collected demographic and epidemiologic data. Predictors associated with being in a cluster were analyzed in a multivariate logistic regression model.


RESULTS
Isolates from 793 patients (430 men) were identified; 137 (17.3%) were considered to be in clusters. After adjustment for multiple potential predictors, we found that the following patients were more likely to be part of a cluster: Canadian-born Aboriginals (v. foreign-born patients) (adjusted odds ratio [OR] 6.0, 95% confidence interval [CI] 3.0-11.7), Canadian-born non-Aboriginals (v. foreign-born patients) (adjusted OR 3.6, 95% CI 2.1-6.3), and injection drug users (v. patients who did not inject drugs) (adjusted OR 3.9, 95% CI 1.9-8.1). Patients with a prior history of tuberculosis were less likely to be part of a cluster than were patients with no history of tuberculosis (adjusted OR 0.3, 95% CI 0.1-0.8).


CONCLUSIONS
Our findings indicate the need to target groups at high risk of tuberculosis more aggressively to prevent transmission and to treat latent infection. DNA fingerprinting may be a useful adjunct to conventional epidemiologic methods to monitor the transmission of tuberculosis in an inner-city setting.
Hernández-Garduño
Eduardo
E
Department of Medicine, University of British Columbia, and BC Centre for Disease Control, Vancouver.
Kunimoto
Dennis
D
Wang
Lei
L
Rodrigues
Mabel
M
Elwood
R Kevin
RK
Black
William
W
Mak
Sunny
S
FitzGerald
J Mark
JM
D000328:Adult; D000368:Aged; D001955:British Columbia / Q000453:epidemiology; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D005260:Female; D006801:Humans; D007198:Indians, North American / Q000706:statistics & numerical data; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology / Q000379:methods; D015999:Multivariate Analysis; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D020380:Needs Assessment; D012150:Polymorphism, Restriction Fragment Length; D011159:Population Surveillance; D011237:Predictive Value of Tests; D012111:Residence Characteristics / Q000706:statistics & numerical data; D012307:Risk Factors; D015819:Substance Abuse, Intravenous / Q000150:complications; D014376:Tuberculosis / Q000453:epidemiology* / Q000382:microbiology* / Q000517:prevention & control / Q000635:transmission; D014504:Urban Health / Q000706:statistics & numerical data
D004269:DNA, Bacterial