Volume 30, Number 10—October 2024
Dispatch
Chlorine Inactivation of Elizabethkingia spp. in Water
Table 2
Inactivation kinetic model performance metrics, rate constant estimates, and disinfectant CT values needed to achieve a 99%–99.99% reduction in Elizabethkingia detection in study of chlorine inactivation of Elizabethkingia spp. in water*
| Comparison |
N |
No. (%) ND |
AIC |
RMSE |
Rate constant (SE),† min–1 |
Pooled SE‡ |
z-score (p value) |
CT value, mg·min/L |
|||
|---|---|---|---|---|---|---|---|---|---|---|---|
| k’ |
ln(k) |
99% |
99.9% |
99.99% |
|||||||
| Model, all data | |||||||||||
| Chick-Watson | 83 |
21 (20) |
430 | 3.1 | 0.89 (0.08) |
10.4 (1.3) | NA |
NA |
0.021 | 0.031 | 0.042 |
| Hom |
431 |
3.0 |
22.1 (18.4) |
0.021 |
0.026 |
0.029 |
|||||
| Species, Chick-Watson model | |||||||||||
| E. anophelis | 35 | 15 (30) | 183 | 3.0 | 0.90 (0.13) | 10.3 (1.8) | 2.5 |
0.10 (0.92) |
0.019 | 0.029 | 0.039 |
| E. meningoseptica |
48 |
6 (11) |
248 |
3.0 |
0.88 (0.11) |
10.0 (1.8) |
0.023 |
0.035 |
0.047 |
||
| Source,§ Chick-Watson model | |||||||||||
| Clinical | 51 | 18 (26) | 280 | 3.5 | 0.90 (0.09) | 10.0 (1.9) | 2.2 | 0.90 (0.37) | 0.021 | 0.032 | 0.043 |
| Environmental | 27 | 0 (0) | 120 | 2.0 | 1.09 (0.13) | 8.1 (1.1) | 0.025 | 0.037 | 0.050 | ||
*AIC, Akaike information criterion; CT value, product of concentration and contact time required to achieve specified reduction; N, number of observations (out of 104 total) with detectable Elizabethkingia used to fit model; ND, not detected; RMSE, root mean square error. †Point estimates and SEs of the disinfectant decay rate constant k’ and natural logarithm of the inactivation rate constant k. ‡Pooled SE for z-test of the equality of rate constants for each subset, obtained as the square root of the sum of the squared standard errors of both rate constant estimates. §The E. anophelis type strain DSM 23781 was isolated from an insect host and thus excluded from the comparison of clinical and environmental sources.