TABLE 2.
Characterization of TnphoA mutants of E. tarda PPD130/91
| Parameter |
E. tarda
straina
|
|||||
|---|---|---|---|---|---|---|
| PPD130/91 | P1 | 153 | 348 | 387 | 392 | |
| Growthb in: | ||||||
| TSA | ++ | + | ++ | ++ | ++ | ++ |
| TSB | ++ | + | ++ | ++ | ++ | ++ |
| PLM | ++ | + | ++ | ++ | ++ | + |
| ROI productionc | + | ++ | ++ | ++ | ++ | ++ |
| Intracellular replication in phagocytesd | ++ | + | ++ | + | ++ | ++ |
| pH sensitivitye | R | S | R | S | R | R |
| Serum resistance | 1.9 ± 0.3 A | 1.3 ± 0.4 A | 1.2 ± 0.7 A | 1.6 ± 0.4 A | 1.6 ± 0.4 A | 1.7 ± 0.4 A |
| LD50 | 105.2 | 106.0 | 105.7 | 105.4 | 106.2 | 105.5 |
| Adherence to EPC cells (%) | 5.2 ± 0.2 A | 4.37 ± 0.4 A | 5.9 ± 0.6 A | 4.6 ± 0.7 A | 3.8 ± 0.2 A | 4.2 ± 0.4 A |
| Internalization into EPC cells (%) | 7.3 ± 0.6 A | 1.9 ± 0.6 B | 3.6 ± 0.8 B | 4.3 ± 1.2 B | 2.6 ± 0.7 B | 2.7 ± 0.5 B |
a
Within each row, values followed by different letters (A or B) are significantly different (P < 0.05).
b
+, little growth; ++, significant growth.
c
++, elevated production of ROI compared to that of the wild type (+).
d
+, decreased rate of intracellular replication compared to the that of wild type (++).
e
R and S, resistance and sensitivity to low pH (5.8 ± 0.1), respectively.