TABLE 3.
Effect of defective MexAB repressors on meropenem susceptibility among 1,055 isolates with presumptively intact MexA and MexB
| Genotype | Predicted OprD loss, OprD missense mutations, or carbapenemase gene presence | Median MIC (IQRa [mg/L]) | No. (%) of nonsusceptible isolates |
|---|---|---|---|
| MexR, NalC, and NalD intact (n = 878) | Yes (n = 501) | 8 (8–16) | 461 (92.0) |
| No (n = 377) | 0.5 (0.25–1) | 38 (10.1) | |
| MexR loss (n = 65) | Yes (n = 47) | 16 (8–32) | 40 (85.1) |
| No (n = 18) | 2 (1–8) | 7 (38.9) | |
| NalC loss (n = 38) | Yes (n = 24) | 12 (8–28) | 22 (91.2) |
| No (n = 14) | 1 (0.25–2.5) | 3 (21.4) | |
| NalD loss (n = 78) | Yes (n = 64) | 16 (8–32) | 62 (96.7) |
| No (n = 14) | 2 (1.75–2) | 2 (14.3) |
a
IQR, interquartile range.