Figure 1Distribution of virulence genes relative to serotypes of Shiga toxin-producing Escherichia coli (STEC) strains. A: eaeA, hlyA, espADB, tir; B: eaeA-, hlyA, espADB, tir; C: eaeA, hlyA-, espADB, tir; D: eaeA, hlyA, espAD-B, tir; E: eaeA, hlyA, espADB, tir-; F: eaeA, hlyA, espADB-, tir-; G: eaeA, hlyA, espA-DB-, tir-; H: eaeA-, hlyA-, espA-D-B-, tir-.
Table 1Primers used in this study
Target gene |
Primer sequence (5′ to 3′) |
Size of the PCR product (bp) |
Shiga toxin 1 (stx1) |
CGTACGGGGATGCAGATAAATCGC |
210 |
CAGTCATTACATAAGAACGCCCAC |
Shiga toxin 2 (stx2) |
GTTCTGCGTTTTGTCACTGTCAC |
326 |
GTCGCCAGTTATCTGACATTCTGG |
Heat-stable enterotoxin (east1) |
ATGCCATCAACACAGTATATCCG |
119 |
TCAGGTCGCGAGTGACGGCTTT |
Attaching and effacing (eaeA) |
ATGCTGGCATTTGGTCAGGTCGG |
233 |
TGACTCATGCCAGCCGCTCATGCG |
Heat-labile toxin (lt) |
GATCACGCGAGAGGAACACAAACC |
366 |
ATCTGTAACCATCCTCTGCCGGAG |
Heat-stable toxin (st) |
CTTTCCCCTCTTTTAGTCAGTC |
302 |
CACAGGCAGGATTACAACAAAGT |
Invasion-associated locus (ial) |
GTTGCGCTTGATGGGTGGGGTATC |
356 |
GAAATGTCCATCAAACCCCACTC |
Hemolysin (hlyA) |
GCATCATCAAGCGTACGTTCC |
519 |
AATGAGCCAAGCTGGTTAAGCT |
Type III secretion protein (espA) |
GTTTTTCAGGCTGCGATTCT |
187 |
AGTTTGGCTTTCGCATTCTT |
Type III secretion protein (espD) |
AAAAAGCAGCTCGAAGAACA |
145 |
CCAATGGCAACAACAGCCCA |
Type III secretion protein (espB) |
GCCGTTTTTGAGAGCCAGAA |
106 |
AAAGAACCTAAGATCCCCA |
Translocated intimin receptor (tir) |
GCTTGCAGTCCATTGATCCT |
107 |
GGGCTTCCGTGATATCTGA |
Autoinducer-2 synthetase (luxS) |
GTCGACGCCGCTGATACCGAACCG |
792 |
GTCGACGCGGTGCGCACTAAGTACAA |
Table 2Distribution of virulence genes in pathogenic Escherichia coli from diarrhoeal patients
Pathogen (n) |
Major genes (n) |
Virulence genes (%)
|
eaeA |
lt
|
st
|
east1 |
ial
|
hlyA |
espA |
espD |
espB |
tir
|
luxS |
STEC (49) |
stx1 only (22) |
12 (55) |
0 (0) |
0 (0) |
3 (14) |
0 (0) |
14 (64) |
14 (64) |
13 (59) |
14 (64) |
13 (59) |
22 (100) |
stx2 only (17) |
13 (77) |
1 (6) |
0 (0) |
2 (12) |
0 (0) |
13 (77) |
11 (65) |
13 (77) |
11 (65) |
12 (71) |
16 (94) |
stx1 and 2 (10) |
7 (70) |
1 (10) |
0 (0) |
3 (30) |
0 (0) |
8 (80) |
6 (60) |
7 (70) |
5 (50) |
5 (50) |
10 (100) |
EPEC (20) |
eaeA (20) |
20 (100) |
2 (10) |
0 (0) |
5 (25) |
0 (0) |
2 (10) |
11 (55) |
20 (100) |
20 (100) |
11 (55) |
11 (55) |
ETEC (20) |
lt (6) |
0 (0) |
6 (100) |
0 (0) |
3 (50) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
6 (100) |
st (1) |
0 (0) |
0 (0) |
1 (100) |
1 (100) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
1 (100) |
lt and st (13) |
0 (0) |
13 (100) |
13 (100) |
13 (100) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
13 (100) |
EAEC (20) |
east1 (20) |
0 (0) |
0 (0) |
0 (0) |
20 (100) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
14 (70) |
EIEC (2) |
ial (2) |
1 (50) |
2 (100) |
0 (0) |
0 (0) |
2 (100) |
0 (0) |
1 (50) |
1 (50) |
1 (50) |
1 (50) |
1 (50) |
Table 3Prevalence of serotypes in pathogenic Escherichia coli from diarrhoeal patients
Pathogen (n) |
Serogroups (n) |
STEC (49) |
O157 (13), O26 (10), O103 (6), O111 (4), O121 (4), O55 (3), O91(3), O117 (2), O2 (1), O21 (1), O104 (1), O119 (1) |
EPEC (20) |
OUT∗ (8), O26 (2), O1 (1), O11 (1), O110 (1), O119 (1), O139 (1), O142 (1), O152 (1), O159 (1), O35 (1), O63 (1) |
EAEC (20) |
OUT (3), O169 (2), O20 (2), O153 (2), O158 (1), O18 (1), O8 (1), O124 (1), O114 (1), O25 (1), O166 (1), O15 (1), O146 (1), O5 (1), O51 (1) |
ETEC (20) |
O6 (8), O20 (3), O8 (2), O25 (2), OUT (2) O9 (1), O15 (1), O102 (1) |
EIEC (2) |
OUT (2) |
Table 4Serogroups in association with stx genes
Presence of stx genes (n) |
Serogroups (n) |
stx1 only |
O26 (8), O103 (6), O55 (3), O91 (2), O21 (1), O111 (1) |
stx2 only |
O157 (7), O26 (2), O121 (4), O111 (1), O2 (1), O104 (1), O119 (1) |
stx1 and stx2 |
O157 (6), O111 (2), O117 (2) O91 (1) |
Table 5Expression of stx genes in Shiga toxin-producing Escherichia coli O157 strains
Strains |
Genotype (PCR)
|
real-time RT PCR
|
RPLA titre
|
stx1 |
stx2 |
stx1 |
stx2 |
Stx1 |
Stx2 |
1 |
Neg. |
Pos. |
0 |
4738 |
0 |
256 |
2 |
Neg. |
Pos. |
0 |
5 |
0 |
0 |
3 |
Neg. |
Pos. |
0 |
3459 |
0 |
4 |
4 |
Neg. |
Pos. |
0 |
1499 |
0 |
4 |
5 |
Neg. |
Pos. |
0 |
3346 |
0 |
256 |
6 |
Neg. |
Pos. |
0 |
11831 |
0 |
256 |
7 |
Neg. |
Pos. |
0 |
2005 |
0 |
256 |
8 |
Pos. |
Pos. |
2740 |
5293 |
32 |
256 |
9 |
Pos. |
Pos. |
1098 |
4673 |
128 |
256 |
10 |
Pos. |
Pos. |
2320 |
5711 |
64 |
256 |
11 |
Pos. |
Pos. |
2135 |
6081 |
64 |
256 |
12 |
Pos. |
Pos. |
1323 |
2164 |
64 |
256 |
13 |
Pos. |
Pos. |
1370 |
2273 |
64 |
256 |