TABLE 2.
Comparison of ID50s for five genotype 2 isolates of C. parvum in mouse and cell culture-based infectivity models
| Isolate | Oocyst doses | CD-1 mice
|
HCT-8 cell RT-PCRa
|
Caco-2 cell RT-PCRa
|
MDCK cell IFAb
|
||||
|---|---|---|---|---|---|---|---|---|---|
| ID50 (oocysts)c | 95% confidence interval (oocysts)d | ID50 (oocysts) | 95% confidence interval (oocysts) | ID50 (oocysts) | 95% confidence interval (oocysts) | ID50 (oocysts) | 95% confidence interval (oocysts) | ||
| Iowa | 50-1,000 | 347 (220) | 128-942 (18) | 106 (77) | 52-154 (13) | 629 (327) | 237-1,669 (12) | 0.5 (24)e | 0.02-13 (14) |
| TAMU | 5-25 | 23 (25) | 17-32 (15) | 27 (34) | 21-34 (11) | 31 (58) | 17-33 (11) | 18 (17) | 6-53 (11) |
| Moredun | 25-500 | 16 (28) | 9-25 (25) | 30 (26) | 18-38 (21) | 45 (40) | 28-70 (22) | 1.2 (5) | 0.6-2 (16) |
| Maine | 25-250 | 21 (22) | 10-40 (21) | 86 (84) | 66-114 (22) | 118 (104) | 89-156 (20) | 13 (20) | 2-78 (11) |
| Glasgow | 25-250 | 21 (27) | 13-34 (20) | 81 (81) | 60-110 (22) | NDf | ND | 1.5 (3) | 0.4-7 (11) |
Infection was detected by RT-PCR.
Infection was detected by immunofluorescence microscopy.
ID50s were calculated by solving the logistic regression of each dose-response curve for a logit response of 0, using individual percentages of infectivity for each replicate dose of oocysts or by first averaging the percentages of infectivity for all replicates and then performing the logit transformation (values in parentheses).
The 95% confidence intervals of the ID50s were calculated from the logistic regression by using individual percentages of infectivity for each replicate dose of oocysts. The numbers in parentheses are the numbers of cages of mice or sets of cell culture wells used to calculate the ID50 and the 95% confidence intervals from the logistic regression by using individual percentages of infectivity for each replicate dose of oocysts. The total numbers of animals or wells of cell cultures used to generate the values can be approximated by multiplying these numbers by 10.
Iowa oocysts were incubated in 0.75% sodium taurocholate prior to inoculation of MDCK cell monolayers.
ND, not done.