Table 3.
Comparison of total blood culture yield and retrieval of B. pseudomallei and Salmonella Paratyphi A over different surveillance periods
| Period 1 (2010–2015) | Period 2 (2016–2018) | Period 3 (2018–2019) | Test for trend over time | |
|---|---|---|---|---|
| Number of months of surveillance | 66 | 24 | 16 | – |
| Pathogen growth rate | 10.7% | 7.1%** | 7.0% | P < 0.001 |
| Total number of cultures sampled | 11,671 | 5,732 | 4,028 | – |
| Mean per month | 177 | 239** | 252** | P < 0.001 |
| Total number of pathogens retrieved | 1,087 | 387 | 277 | – |
| Mean per month | 16.5 | 16.1 | 17.3 | P = 0.25 |
| Retrieved on BS (% of all pathogens) | 73 (6.7) | 37 (9.6) | 125 (45.1) ** | P < 0.001 |
| Total number of B. pseudomallei retrieved (% of all pathogens) | 90 (8.3) | 48 (12.4)** | 12 (4.3)** | – |
| Mean per month | 1.4 | 2.0* | 0.8** | P = 0.53 |
| Retrieved on BS (% of all B. pseudomallei) | 55 (55.6) | 28 (56.0) | 9 (75.0) | P = 0.002 |
| Total number of Salmonella Paratyphi A (% of all pathogens) | 147 (13.5) | 74 (19.1) | 110 (39.7) | – |
| Mean per month | 2.2 | 3.1* | 6.9** | P < 0.001 |
| Retrieved on BS (% of all Salmonella Paratyphi A) | 1 (0.1) | 0 (0.0) | 71 (65.5)** | P < 0.001 |
BS = blind subculture; B. pseudomallei = Burkholderia pseudomallei. Pathogen growth rate was defined as proportion of blood cultures showing growth of a pathogen. Statistically significant differences with the previous surveillance period are indicated with asterisks (* = P < 0.05; ** = P < 0.001). Logistic and Poisson regressions were used to detect a linear trend over time. This table shows that pathogen growth rate significantly declined in periods 2 and 3, but that the total number of pathogens retrieved remained stable. The total number of Salmonella Paratyphi A retrieved showed an increasing trend, whereas the total number of B. pseudomallei retrieved increased in period 2 but decreased significantly in period 3.