Table 1.
Acyclovir Resistance in Serial Clinical Isolates
| Virus Isolate | Source/Day of Illness | Phenotypic Resistance to Acyclovir, IC50 (μmol/L)a | Frequency of Resistant Variants (%)b |
|---|---|---|---|
| D-1 | Mouth lesion, day 19c | 23.1 | 0.23 (23.3) |
| D-2 | Eye, day 19 | 20.9 | 0.49 (49.1) |
| D-3 | Oropharyngeal swab, day 19 | 24.0 | 0.28 (27.5) |
| D-4 | Eye, day 53 | 3.1 | 0.13 (1.32) |
| D-5 | Tongue lesion, day 102 | 3.6 | 2.0 × 10−3 (0.20) |
| D-6 | Eye, day 144 | 30.2 | 0.46 (46.4) |
| KOS | Reference strain | 8.0 | 5.9 × 10−3 (0.59) |
| I-309 | Reference strain | 77.7 | Unable to quantify |
| 615.8 | Reference strain | 16.9 | 0.44 (43.6) |
Abbreviation: IC50, median inhibitory concentration.
aDetermined by plaque reduction using Hill slope method. Breakpoint for resistance is generally IC50 ≥ 8.9 µmol/L (2 µg/mL) acyclovir [2, 10].
bDetermined by plating efficiency assay as described in “Methods.”
cTreatment with acyclovir began 6 days into the illness.