Table 1.
Performance statistics for clonotype-based susceptibility predictions for the primary collection of clinical Escherichia coli isolatesa
| Antibiotics usedb | Observed resistance rate (%)d | Performance of clonotype-based choice of antimicrobial (%)c |
||
|---|---|---|---|---|
| Rejected/resistance | Allowed/resistance | Improvemente | ||
| AMPf | 51.6 | 77.7/60.1 | 22.3/21.9 | 57.5 |
| TETf | 29.5 | 49.4/48.0 | 50.6/11.5 | 61.1 |
| A/Sf | 29.4 | 66.2/37.9 | 33.8/13.0 | 55.9 |
| T/S | 26.9 | 42.0/50.1 | 58.0/10.1 | 62.4 |
| A/K | 25.5 | 51.9/36.5 | 48.1/13.5 | 46.8 |
| CZ | 19.7 | 42.0/32.0 | 58.0/10.7 | 45.4 |
| CIP | 17.1 | 20.6/68.7 | 79.4/3.7 | 78.1 |
| GMf | 8.92 | 17.1/31.4 | 82.9/4.3 | 52.1 |
| NIT | 6.79 | 5.9/27.4 | 94.1/5.5 | 19.2 |
| CTR | 5.38 | 4.3/31.1 | 95.7/4.2 | 21.6 |
| PTZ | 3.96 | 2.1/13.3 | 97.9/3.8 | 5.1 |
A total of 1,518 isolates were typed using a fumC-fimH (CH) scheme and were tested against 11 antimicrobials. Of the isolates, 1,413 out of 1,518 belonged to CH clonotypes that contained >1 isolate (nonsingletons).
AMP, ampicillin; TET, tetracycline; A/S, ampicillin-sulbactam; T/S, trimethoprim-sulfamethoxazole; A/K, amoxicillin-clavulanate; CZ, cefazolin; CIP, ciprofloxacin; GM, gentamicin; NIT, nitrofurantoin; CTR, ceftriaxone; PTZ, piperacillin-tazobactam.
For each isolate, the treatment with an antimicrobial agent was allowed or not based on the prevalence of the susceptibility to this agent in the respective CH clonotype; to avoid bias, each analyzed isolate was excluded from the calculation of prevalence.
Rate (%) of resistant isolates among 1,413 isolates.
Percent improvement toward ideal test (100%) was calculated as (difference between the CH and antibiogram approach)/(difference between the antibiogram approach and 100%) × 100; all improvement rates were statistically significant (P < 0.001, Fisher's exact test), except for with NIT and CTR (P = 0.09) and PTZ (P = 0.43).
Antimicrobials with comparatively limited clinical utility.