TABLE 2.
Summary of in vitro susceptibilities of E. faecium isolates to quinupristin-dalfopristin
| Group (age [days]) | No. (%) of resistanta isolates/total | No. (%) of animals with resistant strains/no. with E. faecium | Total no. of animals with culture (% of animals with resistant E. faecium) |
|---|---|---|---|
| 1 (24)b | 4/17 (23) | 4/13 (31) | 20 (20) |
| 2 (28)c | 0/0 (0) | 0/21 (0) | 25 (0) |
| 3 (59) | 3/16 (19) | 3/15 (20) | 20 (15) |
| 4 (80) | 9/16 (56) | 7/13 (54) | 20 (35) |
| 5 (130) | 9/9 (100)d | 5/5 (100)e | 20 (25) |
a
MIC of ≥4.0 defines resistance.
b
Groups 1 and 5 are the same flock (P = 0.0002 for isolates; P = 0.01 for group 1 versus group 5 animals).
c
Groups 2 and 3 are the same flock (P = 0.9 for isolates; P = 0.05 for group 2 versus group 3 animals).
d
P = 0.07 for comparison of isolates in groups 1 through 5.
e
P = 0.14 for comparison of animals in groups 1 through 5.