TABLE 4.
Survival of F. tularensis strains in A. castellanii in the presence and absence of encystment
| Time (days) | Result(s) after indicated treatmenta |
|||||||
|---|---|---|---|---|---|---|---|---|
| SCHU |
Ft-1 |
NOV |
LVS |
|||||
| − C | + C | − C | + C | − C | + C | R | + R | |
| 3 | +, E | NG, NE | +, E | NG, NE | +, E | NG, NE | + | +, E |
| 8 | +, E | NG, NE | +, E | NG, NE | +, E | NG, NE | NG | +, E |
| 14 | +, E | ND | +, E | ND | +, E | ND | NG | NG |
A. castellanii trophozoites were treated with (+ C) or without (− C) 25 μg/ml cycloheximide to prevent encystment or A. castellanii amoebae were infected with LVS in the presence (+ R) or absence (− R) of the REP fractions from NOV-A. castellanii or SCHU-A. castellanii cocultures. +, turbidity was observed in experimental wells 48 to 72 h after replacement of buffer with rich medium (F. tularensis growth was confirmed by plating for viable CFU and gram staining; in all cases where turbidity was observed, >108 CFU/ml were present); E, at least 50% of A. castellanii amoebae present were encysted; NG; no growth after replacement of buffer with rich medium and plating for viable CFU; NE, less than 10% of A. castellanii amoebae present were encysted; ND, not done.