Table 5.
E. coli isolates with resistance phenotypes not explained by detection of a corresponding gene by microarray
| Unexplained resistance phenotype(s)a | No. of isolates | Molecular finding(s) (no. of isolates tested) |
|---|---|---|
| A | 3 | Chromosomal ampC mutationb (2) |
| A, Amc | 1 | Chromosomal ampC mutation |
| A, Amc, G | 1 | NDc |
| A, Caz | 1 | Chromosomal ampC mutation |
| A, Caz, Amc | 1 | Chromosomal ampC mutation |
| A, G | 1 | ND |
| A, G, Sxt | 1 | ND |
| Amik | 6 | rmtEd |
| G | 1 | ND |
| G, Amik | 2 | rmtE |
| G, Amik, Sxt | 3 | rmtE and novel dhfr gene (2) rmtE, Sxt resistance unexplained (1)e |
| G, Sxt | 1 | ND (PCR negative for novel dhfr gene) |
| Sxt | 1 | Novel dhfr gene |
| T, C, Sxt | 1 | ND (PCR negative for novel dhfr gene) |
| T, G | 1 | Probe for aac(3)-II was not on the array, T unexplained |
a
A, ampicillin; Amc, amoxicillin-clavulanic acid; Amik, amikacin; C, chloramphenicol; Caz, ceftazidime; G, gentamicin; K, kanamycin; Nal, nalidixic acid; S, streptomycin; Su, sulfisoxazole; Sxt, trimethoprim-sulfamethoxazole.
b
Reference 35.
c
ND, not determined.
d
Reference 16.
e
Not PCR assayed yet for novel dhfr gene.