Interactions of Neuropathogenic Escherichia coli K1 (RS218) and Its Derivatives Lacking Genomic Islands with Phagocytic Acanthamoeba castellanii and Nonphagocytic Brain Endothelial Cells

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.