Volume 19, Number 5—May 2013
CME ACTIVITY - Research
Transmission of Mycobacterium tuberculosis Beijing Strains, Alberta, Canada, 1991–2007
Deanne Langlois-Klassen, Ambikaipakan Senthilselvan, Linda Chui, Dennis Kunimoto, L. Duncan Saunders, Dick Menzies, and Richard Long
Table 4
Risk factors for the recent transmission of Mycobacterium tuberculosis among index case-patients born in Alberta, Canada, in the Western Pacific, 1993–2007
| Characteristic | Index case-patients |
Secondary case-patients | Transmission index* | Relative transmission index (95% CI)† |
||
|---|---|---|---|---|---|---|
| Nonclustered | Clustered | Unadjusted | Adjusted | |||
| Sex | ||||||
| F | 122 | 9 | 10 | 0.08 | 1.0 | |
| M |
195 |
9 |
10 |
0.05 |
0.6 (0.3–1.5) |
|
| Age at diagnosis, y | ||||||
| <35 | 83 | 5 | 5 | 0.06 | 1.0 | |
| 35–64 | 110 | 4 | 4 | 0.04 | 0.6 (0.2–2.3) | |
| >64 |
124 |
9 |
11 |
0.08 |
1.5 (0.5–4.2) |
|
| Sputum smear status‡ | ||||||
| Negative | 174 | 7 | 7 | 0.04 | 1.0 | 1.0 |
| Positive |
126 |
9 |
11 |
0.08 |
2.1 (0.8–5.4) |
2.1 (0.8–5.5) |
| Bacillary load§ | ||||||
| Low | 53 | 3 | 5 | 0.09 | 1.0 | |
| High |
17 |
1 |
1 |
0.06 |
0.6 (0.1–5.3) |
|
| Chest radiography | ||||||
| No cavitation | 252 | 14 | 16 | 0.06 | 1.0 | |
| Cavitation |
65 |
4 |
4 |
0.06 |
1.0 (0.3–2.9) |
|
| Drug resistance | ||||||
| Pan-susceptible | 239 | 13 | 14 | 0.06 | 1.0 | |
| Monoresistance | 51 | 2 | 2 | 0.04 | 0.7 (0.2–3.0) | |
| Polyresistance | 21 | 3 | 4 | 0.17 | 3.0 (1.0–9.1) | |
| Multidrug resistance¶ |
6 |
0 |
0 |
0 |
||
| M. tuberculosis lineage | ||||||
| Non-Beijing | 171 | 9 | 11 | 0.06 | 1.0 | 1.0 |
| Beijing |
146 |
9 |
9 |
0.06 |
1.0 (0.4–2.3) |
0.9 (0.3–2.2) |
| Time since arrival in Canada, y | ||||||
| <2 | 76 | 3 | 3 | 0.04 | 1.0 | |
| 3–5 | 43 | 1 | 1 | 0.02 | 0.6 (0.1–5.8) | |
| 6–10 | 53 | 6 | 6 | 0.10 | 2.7 (0.7–10.7) | |
| >10 |
112 |
8 |
10 |
0.08 |
2.2 (0.6–8.0) |
|
| Total | 317 | 18 | 20 | 0.06 | ||
*The number of secondary cases divided by the number of index cases.
†Bivariate Poisson regression using an offset of 1 each index case.
‡Sputum smear microscopy was not completed with all cases.
§Bacillary load was not included in multivariate modeling because of multicollinearity with sputum smear status.
¶Multidrug-resistant tuberculosis was excluded from bivariate analyses.
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