Table 3. Genetic characteristics and lipid A composition of colistin-resistant Acinetobacter baumannii isolates from patients with and without colistin treatment.
| Colistin-susceptible A. baumannii (N=3)† | Colistin-resistant A. baumannii (N=36) | P | ||
|---|---|---|---|---|
| CT (N=18) | Non-CT (N=18) | |||
| Relative percentage of each lipid A component peak (%)* | ||||
| Hexa | 39.8 (29.8–40.6) | 13.3 (2.1–49.7) | 24.7 (0–58.1) | 0.021 |
| Hexa+1-PE | 0 (0–1.0) | 21.2 (8.3–146.9) | 24.3 (2.1–78.5) | 0.448 |
| Hexa+2-PE | 0 (0–0) | 2.1 (0–43.3) | 0 (0–3.7) | 0.008 |
| Hepta | 100 (100–100) | 100 (100–100) | 100 (100–100) | - |
| Hepta+1-PE | 0 (0–1.0) | 143.5 (63.5–353.4) | 108.6 (62.2–204.7) | 0.018 |
| Hepta+2-PE | 0 (0–0) | 29.4 (0–71.1) | 1.9 (0–31.6) | < 0.001 |
| Octa | 9.1 (2.2–12.9) | 5.5 (0–11.6) | 6.6 (0–12.6) | 0.355 |
| Octa+1-PE | 0 (0–0) | 47.3 (15.2–137.7) | 58.9 (25.7–316.7) | 0.393 |
| Octa+2-PE | 0 (0–0) | 51.3 (0.3–220.8) | 5.8 (1.7–255.7) | 0.002 |
| Octa+2-PE+4C-H2O | 0 (0–0) | 16.3 (0–100.7) | 0 (0–58.2) | 0.001 |
| Isolates with genetic mutations, N (%) | ||||
| Overall | 0 (0%) | 13 (72.2%) | 2 (11.1%) | < 0.001 |
| pmrB | 13 (72.2%) | 2 (11.1%) | < 0.001 | |
| pmrC | 4 (22.2%) | 2 (11.1%) | 0.658 | |
| lpsB | 1 (5.6%) | 0 (0%) | 1.000 | |
Bold values are statistically significant (P<0.05).
*Data represent the relative intensity (%) and their range compared with hepta-acylated lipid A, set as 100%.
†For comparison, three randomly selected colistin-susceptible Acinetobacter baumannii clinical isolates were used as controls.
Abbreviations: CT, colistin treatment; Hexa, hexa-acylated lipid A; Hepta, hepta-acylated lipid A; Octa, octa-acylated lipid A; PE, phosphoethanolamine; C, carbon.