Table 3.
RS218-derived islands (RDI's) mutants and their interactions with human brain microvascular endothelial cells (HBMEC). For associated, invasion, and survival assays, the number of E. coli K1 c.f.u. interacting with HBMEC was considered as 100% and the results of mutant strains are expressed as the relative change. For cytotoxicity assays, E. coli K1-mediated HBMEC death was considered as 100% and the results of mutant strains are expressed as the relative change.
| E. coli | HBMEC | |||
|---|---|---|---|---|
| Association | Invasion | Survival | Cytotoxicity | |
| K1 (RS218) | 100 | 100 | 100 | 100 |
| Plasmid cured RS218 | 27.41 ± 4.5* | 92.52 ± 5.6* | 70.86 ± 6* | 104 ± 7.8 |
| Black hole filled with HB101 DNA | 31 ± 1.6* | 62.86 ± 13* | 163.5 ± 28* | 87 ± 10 |
| RDI 1 | 89.97 ± 1.2 | 112.8 ± 10.6 | 96.56 ± 8 | 97 ± 13 |
| RDI 2 | 98.42 ± 2.6 | 72.5 ± 8.7* | 91.6 ± 9.1 | 108 ± 14 |
| RDI 4 | 93.6 ± 3.52 | 98.37 ± 0.8 | 96.76 ± 1.8 | 124 ± 2.3 |
| RDI 9 | 101.47 ± 2.6 | 109.6 ± 4.4 | 106.5 ± 3.4 | 110 ± 12 |
| RDI 10 | 61.12 ± 1.4* | 58.5 ± 6.1* | 55.47 ± 6* | 92.8 ± 3 |
| RDI 12 | 70.7 ± 8.3* | 88.3 ± 7.1 | 107.5 ± 11 | 89.9 ± 9 |
| RDI 14 | 105.84 ± 4.1 | 133.7 ± 22 | 96.7 ± 11 | 103 ± 4 |
| RDI 15 | 53.97 ± 7.5* | 115.9 ± 5.5 | 113.6 ± 3.1 | 118 ± 7 |
| RDI 16 | 67.78 ± 3* | 111 ± 13 | 156.1 ± 19* | 127 ± 5.4 |
| RDI 17 | 104 ± 1 | 69.77 ± 7.4* | 60.4 ± 3.4* | 105 ± 2 |
| RDI 18 | 107.52 ± 1.6 | 159.2 ± 18* | 108.6 ± 8.8 | 88 ± 1.8 |
| RDI 21 | 32.82 ± 4.6* | 25 ± 3.6* | 17.95 ± 3* | 14.5 ± 1.1* |
| RDI 22 | 77.9 ± 8.9* | 61.53 ± 8* | 50.45 ± 7* | 127 ± 3.4 |
(i) Association was calculated as follows: (number of bacterial c.f.u. recovered/original inoculum) × 100 = bacterial association of HBMEC.
(ii) Invasion was calculated as follows: (number of bacterial c.f.u. recovered/original inoculum) × 100 = bacterial invasion of HBMEC.
(iii) Survival was calculated as follows: (number of bacterial c.f.u. recovered/original inoculum) × 100 = bacterial survival of HBMEC.
(iv) Cytotoxicity was calculated as follows: (sample value − negative control value)/(total LDH release − negative control value) × 100 = HBMEC cytoxicity.
*indicates a significant difference (P < 0.05 using paired t-test, one-tailed distribution) when data of mutant strains were compared with the wild type E. coli K1 data.