TABLE 5.
Favorable response rates in 22 patients who received an aminoglycoside as the only effective antibiotic against the infecting organism, as determined by in vitro susceptibility testing, for more than 5 days
| Aminoglycoside MIC/SBPC ratioa | No. of patients with favorable response/no. of patients evaluated (%)
|
|||||
|---|---|---|---|---|---|---|
| ESBL group
|
Non-ESBL group
|
|||||
| 3rd day | 5th day | End of therapy | 3rd day | 5th day | End of therapy | |
| 1/16 | 4/4 | 4/4 | 4/4 | 3/4 | 4/4 | 4/4 |
| 1/8 | 3/4 | 3/4 | 3/4 | 2/3 | 2/3 | 3/3 |
| Subtotalb | 7/8 (87.5) | 7/8 (87.5) | 7/8 (87.5) | 5/7 (71.4) | 6/7 (85.7) | 7/7 (100) |
| 1/4 | 0/1 | 0/1 | 0/1 | |||
| 1/2 | 0/1 | 0/1 | 0/1 | |||
| 1 | 0/5 | 0/5 | 1/5 | |||
| Subtotalc | 0/7 (0) | 0/7 (0) | 1/7 (14.3) | |||
| Totald | 7/15 (46.7) | 7/15 (46.7) | 8/15 (53.3) | 5/7 (71.4) | 6/7 (85.7) | 7/7 (100) |
Aminoglycoside MIC/SBPC ratio, ratio of the MIC of the aminoglycoside administered for the infecting organism to the SBPC of the aminoglycoside administered (that is, 4 μg/ml for gentmicin and 16 μg/ml for amikacin, as recommended by NCCLS [23]). The periods from the onset of bacteremia to the time of administration of aminoglycosides effective in vitro were not significantly different between the ESBL group (1.4 ± 3.07 days) and the non-ESBL group (0.57 ± 0.53 days) (P = 0.085).
The differences in favorable response rates between the ESBL group infected with organisms for which the aminoglycoside MIC/SBPC ratios were ≤1/8 and the non-ESBL group were not statistically significant at the 3rd day (P = 0.45), the 5th day (P = 0.92), and the end of aminoglycoside therapy (P = 0.35).
The differences in favorable response rates between the ESBL group infected with organisms for which the aminoglycoside MIC/SBPC ratios were ≥1/4 and the non-ESBL group were statistically significant at the 3rd day (P = 0.007), the 5th day (P = 0.007), and the end of amonoglycoside therapy (P = 0.002).
The differences in favorable response rates between the ESBL group as a whole and the non-ESBL group were not significant at the 3rd day (P = 0.29 by the Mann-Whitney test) or the 5th day (P = 0.09) but reached statistical significance at the end of aminoglycoside therapy (P = 0.032).