Tuberculosis Paper Summary 2021 Flashcards
Important among certain high risks groups
Aboriginal people •Foreign-born residents from countries with high prevalence of TB •Disadvantaged inner-city populations •HIV-infected people
1995
incidence rate was 6.5 per 100,000
•Currently (2017) 1,800 cases of active TB
reported annually
In BC in 2000
285 cases reported
Tuberculosis
Mycobacterium tuberculosis
(Bacteria; High G+C Gram
+; Actinobacteria)
What is the widely accepted hypothesis that
explains the persistence of tuberculosis in
developed countries?
Hypothesis: Foreign-born people are infected in their
country of origin and then
• primary disease develops shortly after immigration
• people remain at risk for reactivated disease for the rest of
their lives
People with clustered isolates =
same transmission
chain
Molecular biology allowed the development of
what to distinguish between different
M. tuberculosis isolates
fingerprinting method
People with unique isolate =
reactivated cases (origin of isolate in a foreign country)
2 studies in 2002
New York and Denmark
New York
people born outside USA much less likely
to be in cluster group (new transmission chain)
But people less than 10 years in USA and not
HIV positive: half have clustered isolates (new
infections).
Denmark
55% Somali immigrants were clustered,
But unclear if disease acquired in Somalia and
transmitted in Denmark or being transmitted within the
Somali community in Denmark.
What about Greater Vancouver?
Hernandez-Garduno et al. 2002. CMAJ 167:349-345.
Combination of conventional epidemiology with DNA
fingerprinting of M. tuberculosis.
Determine predictors associated with being in a cluster in order to better understand transmission of
tuberculosis in Greater Vancouver.
M. tuberculosis identified by
y biochemical test and RNA
hybridization.
DNA fingerprinting by RFLP using…
insertion sequence IS
6110 as a probe.
when do you use spolingotyping?
Use Spoligotyping if isolates < 6 bands
Divided sample into two groups
Divided sample into two groups Clustered isolates (isolates with identical band patterns) Non-clustered isolates (unique band patterns)
Stat tests
Chi-square, Fisher’s exact test for univariate
analysis to assess risk factors.
Predictors significantly associated with
clustering included in multivariate logistic regression
model.
Results
806 cases
137 into 46 clusters (infer transmission chain)
656 non clustered (not part of transmission chain)
Strongest predictor of clustering:
1.Canadian-born aboriginal vs foreign born (adjusted OR 6.0)
2. Canadian-born non-aboriginal vs foreign born (adjusted OR
3.6)
3. Injection drug user vs patients who did not inject drugs (OR
3.0)
4. Patients with a prior history of tuberculosis less likely to be
part of a cluster than patients with no history of
tuberculosis (adjusted OR 0.3)
Source of transmission chain more likely…
from inner city aboriginal
groups
Not predictors of clustering are
HIV-HIV seropositivity
Antibiotic resistance
odd ratio
Odd Ratio
Relation between obs/expected (total #)
who play an important role in
the transmission of tuberculosis in Greater
Vancouver
Younger Aboriginal people
who play an
important role in the transmission of TB in GV.
Above 60 years-old, non-Aboriginal people
Aboriginal people in
Canada have a gene deletion for what which
may predispose them to acquire TB.
NRAMP1
