Table 1.
Analysis of discordance in phenotypic and/or genotypic resistance predictions for 74 E. coli bloodstream isolates
| Antibiotic | Discrepancies (n; % of total, 74 isolates) |
Agreement of gradient diffusion with genotype in all discrepancies (n/total discrepancies; %) | Agreement of gradient diffusion with genotype in BD Phoenix-concordant discrepancies (n/number of BD Phoenix-concordant discrepancies; %) | ||
|---|---|---|---|---|---|
| S/Ra discordant BD Phoenix | BD Phoenix S/S, genotype R | BD Phoenix R/R, genotype S | |||
| Amoxicillin | 0 (0) | 2 (3) | 0 (0) | 1/2 (50) | 1/2 (50) |
| Co-amoxiclav | 5 (7) | 0 (0) | 15 (20) | 20/20 (100) | 15/15 (100) |
| Gentamicin | 1 (1) | 0 (0) | 0 (0) | 1/1 (100) | NAb |
| Ciprofloxacin | 0 (0) | 0 (0) | 0 (0) | NA | NA |
| Ceftriaxone | 0 (0) | 1 (1) | 1 (1) | 0/2 (0) | 0/2 (0) |
| Ceftazidime | 1 (1) | 11 (15) | 1 (1) | 1/13 (8) | 1/12 (8) |
| Meropenem | 0 (0) | 0 (0) | 0 (0) | NA | NA |
| Total | 7/518 (1)c | 14/518 (3)c | 17/518 (3)c | 23/38 (61) | 17/31 (55) |
aS/R denotes susceptible/resistant category. Initial BD Phoenix intermediate results were counted as resistant—this occurred in one isolate with an S/R discrepancy for ceftazidime and one isolate with an S/R discrepancy for gentamicin.
bNA = not applicable.
cn/overall total of 518 antimicrobial susceptibility results (%).