HeLa cells were grown in 24-well tissue culture plates Selleckchem Y-27632 until they formed GSK3235025 clinical trial semi-confluent monolayers. The culture medium used was RPMI1640 supplemented with 10% fetal calf serum (FCS), and 1% penicillin-streptomycin; and cultures were incubated at 37°C/5% CO2. Cells were washed three times with phosphate-buffered

saline (PBS), and bacteria added to the semi-confluent HeLa cultures at a multiplicity of infection (MOI) of 100. After incubating at 37°C for 90 min, growth medium containing 5% (w/v) agar and 20 μg/mL gentamicin was poured into the 24-well plates, then incubated at 37°C/5% CO2 for 72 h. HeLa cells were inoculated with SF301 as a positive control, and with E. coli ATCC 25922 as a negative control. Sequence and analysis of virulence genes on PAI-1 of SF51 SF51 genomic DNA was extracted using a QIAamp DNA Mini Kit (Qiagen). PCR primers for amplification of pic, sigA, int and

orf30 from PAI-1 of the SF51 clinical isolate were designed according to the SF301 sequence. Amplicons were cloned into a pCR-XL-TOPO vector using a TOPO® XL PCR Cloning Kit (Invitrogen), and the inserts were sequenced by Sangon Selleck mTOR inhibitor Biotech (Shanghai, China) Co. Ltd, then identified using the standard nucleotide basic local alignment search tool (BLASTn; NCBI). Construction of SF301-∆ pic The upstream and downstream portions of pic were amplified by PCR. Primers uppic-F-NotI and uppic-R-XbaI (Table 1) were used to amplify the upstream fragment of pic, with primers

downpic-F-XbaI and downpic-R-BamHI Carbohydrate (Table 1) used to amplify the downstream fragment. The amplified downstream fragment of pic was digested with XbaI and BamHI and ligated into pSB890 which had been cut with the same restriction endonucleases [27]. We designated the resulting plasmid pSB890-pic downstream. The amplified upstream pic fragment was digested with NotI and XbaI and ligated into pSB890-pic downstream that had been digested with NotI and XbaI. The resulting vector was designated pSB890-∆ pic and transformed into E. coli SM10 λpir cells, then introduced into SF301 through a bacterial conjugation test. After culturing on a sucrose LB agar plate at 22°C, sucrose-tolerant colonies were screened using Shigella-specific minimal medium [7] and a PCR employing primers Upuppic-F and Downdownpic-R (Table 1). The mutant strain with the pic deletion was identified by sequencing and named SF301-∆ pic. Construction of complementation strains SF301-∆ pic/pPic and SF51/pPic A plasmid containing pic was constructed using pSC modified from pREP4. The pic gene was amplified from SF301 genomic DNA using PCR. The PCR primers used were pic-pSC-F-PfMlI and pic-pSC-R-AclI (Table 1). Amplicons were inserted into pSC, creating pSC-pic, which was verified by restriction enzyme digestion and nucleic acid sequencing.