Using agarose gel electrophoresis analysis. Amp-resistant and Km-resistant transformants were cured of pMD20-oriR and I-BRD9 pUCK-repB by subculturing in LB broth without Amp and Km. The absence of pO157 was confirmed by PCR with primers for the pO157-specific genes ecf and ehx [21,22]. The integrity of chromosomal DNA was confirmed using Pulsed field gel electrophoresis (PFGE).Cytokine AssayAt 2 and 4 h postinfection, the supernatants of the cell cultures were collected and the levels of human cytokines IL-6, IL-8, chemokine CC motif ligand 5 (RANETS/CCL5), monocyte chemotactic protein-1 (MCP-1), TNF-a, interferon-gamma (IFNc), and IL-1b were 
quantified using a Luminex Kit in accordance with the manufacturer’s instructions (R D Systems, Minneapolis, MN, U.S.). Differentiated THP-1 with culture medium alone served as a control for the spontaneous release of cytokine. LPS (1 mg/ml) (E. coli O111, Sigma) served as a positive control.RT-PCR AnalysisAt 2 and 4 h postinfection, total RNA from differentiated THP1 cells was isolated using an RNeasy Mini Kit (Qiagen, 301-00-8 Hilden, Germany) and digested with RNase-free DNase I (Promega). Then cDNA was synthesized using Superscript II reverse transcriptase and random hexamers according to the manufacturer’s guidelines (TaKaRa Bio, Dalian, China). The cDNA was amplified using semiquantitative PCR using SYBR green I master mix (TakaRa) and specific primers (Table 1) using the Rotor-Gene Q (Qiagen). Relative expression of target genes were calculated as 22DDCT. DDCT = [(CT gene of interest ?CT internal control) sampleA ?(CT gene of interest ?CT internal control) sampleB] [24]. The mRNA expression level of each target gene was normalized to that of glyceraldehyde-3-phosphate dehydrogenase (GAPDH).Construction of the ehxA Gene Deletion MutantThe EDL933 ehxA deletion mutant (DehxA) was constructed using the linear recombination (lRed) method described by Datsenko and Wanner [20]. Briefly, the primer ehxA-1,2 (Table 1) was used to amplify the Km resistance cassette from plasmid template pRS551 using PCR. The resulting product was then transformed by electroporation into EDL933-competent cells. EDL933 carrying pKOBEG, grown at 30uC in the presence of 10 mM arabinose. pKOBEG was removed by shaking for 15 minutes in a water bath at 42uC. Mutants were selected on LB-Km plates and confirmed by PCR using primers ehxA-3,4 and ehxA-5,6 (Table 1). A strain with the ehxA gene complement was created using arabinose-inducible expression vector pBAD24. The ehxA gene was amplified from purified EDL933 template using PCR with primer ehxAhb (Table 1). The gene was inserted into the XbaI-KpnI sites of pBAD24 and 24786787 transformed by electroporation into the donor strain DehxA,RNA InterferencesiNLRP3, siASC, siCaspase-1, and siControl were synthesized as previously published [25]. A total 
of 56105 THP-1 cells were differentiated with PMA in a 12-well plate. Then the cells wereEnterohemolysin Induced Release of IL-1bTable 1. Primers.Primer oriR repB ehxA-1,Forward (59-39) TTCTGAGGCAGGCTGGTATT ACAATACCGCACAAGCAAC ATGTCAGGCAGATGGAAAGCT ATGACAGTAAATAAAATAAAG AACATTTTCAATAATGCGAA TGAGCCATATTCAACGGGA TTCAGGCAATACCATCAT ACGCACATACAGGAACAA CATGGTACCGACAGTAAATA AAATAAAGAAC ATT GGTATCGTGGAAGGACTCATGAC GGCGGCATCCAGCTACGAATCTC AGTTTGAAGGACAAACCGAAGGT TGGATGCTCTGTACGGGAAGGTC ATCAGTATTGAGCACCAGCCATT GGCACAGTGGTTTCTTAGAGGTA CTCTGTGCGGACTCTACTCTTTG ACCAACATCATCCGTGGCAACCT GAAGGAGACTTGGACGATTTGGC CCTATCAACTGCCCTTCCACAATReverse (59-39) TGTTGCTTGTGCGGTATTGT.Using agarose gel electrophoresis analysis. Amp-resistant and Km-resistant transformants were cured of pMD20-oriR and pUCK-repB by subculturing in LB broth without Amp and Km. The absence of pO157 was confirmed by PCR with primers for the pO157-specific genes ecf and ehx [21,22]. The integrity of chromosomal DNA was confirmed using Pulsed field gel electrophoresis (PFGE).Cytokine AssayAt 2 and 4 h postinfection, the supernatants of the cell cultures were collected and the levels of human cytokines IL-6, IL-8, chemokine CC motif ligand 5 (RANETS/CCL5), monocyte chemotactic protein-1 (MCP-1), TNF-a, interferon-gamma (IFNc), and IL-1b were quantified using a Luminex Kit in accordance with the manufacturer’s instructions (R D Systems, Minneapolis, MN, U.S.). Differentiated THP-1 with culture medium alone served as a control for the spontaneous release of cytokine. LPS (1 mg/ml) (E. coli O111, Sigma) served as a positive control.RT-PCR AnalysisAt 2 and 4 h postinfection, total RNA from differentiated THP1 cells was isolated using an RNeasy Mini Kit (Qiagen, Hilden, Germany) and digested with RNase-free DNase I (Promega). Then cDNA was synthesized using Superscript II reverse transcriptase and random hexamers according to the manufacturer’s guidelines (TaKaRa Bio, Dalian, China). The cDNA was amplified using semiquantitative PCR using SYBR green I master mix (TakaRa) and specific primers (Table 1) using the Rotor-Gene Q (Qiagen). Relative expression of target genes were calculated as 22DDCT. DDCT = [(CT gene of interest ?CT internal control) sampleA ?(CT gene of interest ?CT internal control) sampleB] [24]. The mRNA expression level of each target gene was normalized to that of glyceraldehyde-3-phosphate dehydrogenase (GAPDH).Construction of the ehxA Gene Deletion MutantThe EDL933 ehxA deletion mutant (DehxA) was constructed using the linear recombination (lRed) method described by Datsenko and Wanner [20]. Briefly, the primer ehxA-1,2 (Table 1) was used to amplify the Km resistance cassette from plasmid template pRS551 using PCR. The resulting product was then transformed by electroporation into EDL933-competent cells. EDL933 carrying pKOBEG, grown at 30uC in the presence of 10 mM arabinose. pKOBEG was removed by shaking for 15 minutes in a water bath at 42uC. Mutants were selected on LB-Km plates and confirmed by PCR using primers ehxA-3,4 and ehxA-5,6 (Table 1). A strain with the ehxA gene complement was created using arabinose-inducible expression vector pBAD24. The ehxA gene was amplified from purified EDL933 template using PCR with primer ehxAhb (Table 1). The gene was inserted into the XbaI-KpnI sites of pBAD24 and 24786787 transformed by electroporation into the donor strain DehxA,RNA InterferencesiNLRP3, siASC, siCaspase-1, and siControl were synthesized as previously published [25]. A total of 56105 THP-1 cells were differentiated with PMA in a 12-well plate. Then the cells wereEnterohemolysin Induced Release of IL-1bTable 1. Primers.Primer oriR repB ehxA-1,Forward (59-39) TTCTGAGGCAGGCTGGTATT ACAATACCGCACAAGCAAC ATGTCAGGCAGATGGAAAGCT ATGACAGTAAATAAAATAAAG AACATTTTCAATAATGCGAA TGAGCCATATTCAACGGGA TTCAGGCAATACCATCAT ACGCACATACAGGAACAA CATGGTACCGACAGTAAATA AAATAAAGAAC ATT GGTATCGTGGAAGGACTCATGAC GGCGGCATCCAGCTACGAATCTC AGTTTGAAGGACAAACCGAAGGT TGGATGCTCTGTACGGGAAGGTC ATCAGTATTGAGCACCAGCCATT GGCACAGTGGTTTCTTAGAGGTA CTCTGTGCGGACTCTACTCTTTG ACCAACATCATCCGTGGCAACCT GAAGGAGACTTGGACGATTTGGC CCTATCAACTGCCCTTCCACAATReverse (59-39) TGTTGCTTGTGCGGTATTGT.