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A novel bacteriophage, PBES 02, infecting Cronobacter sakazakii was isolated and characterized. It has a spherical head of 90 nm in diameter and a tail of 130 nm in length, and belongs to Myoviridae as observed under a transmission electron microscope. The major virion protein appears to be 38 kilodaltons (kDa) in size. The latent period of PBES 02 is 30 min and the burst size is 250. Infectivity of the phage remained intact after exposure to temperatures ranging from 4°C to 55°C for 1 h. It was also stable after exposure to pHs ranging from 6 to 10 for 1 h. The phage effectively removed contaminating Cronobacter sakazakii from broth infant formula. PBES 02 has a double-stranded DNA genome of 149,732 bases. Its GC ratio is 50.7%. Sequence analysis revealed that PBES 02 has 299 open reading frames (ORFs) and 14 tRNA genes. Thirty-nine ORFs were annotated, including 24 related to replication and regulation functions, 10 related to structural proteins, and 5 related to DNA packaging. The genome of PBES 02 is closely related to that of two other C. sakazakii phages, CR3 and CR8. Comparison of DNA sequences of genes encoding the major capsid protein revealed a wide geographical distribution of related phages over Asia, Europe, and America.

PA26, a novel lytic bacteriophage infecting Pseudomonas aeruginosa, was isolated, and the whole genome was sequenced. It was found to belong to the myoviridae by an electron microscopic observation. It had a linear double-stranded DNA genome of 72,321 bp. Genomic analysis showed that it resembled another Pseudomonas phage, LIT1.

Background Th17 cells and their main secreting cytokine interleukin-17A (IL-17) are considered as the main pathogenic factors in inflammatory bowel diseases (IBDs). However, anti-IL-17 neutralizing antibodies, a theoretically curative medication for IBDs, paradoxically aggravated intestinal inflammation. The mechanisms by which it mediates the protective and pathologic effects of IL-17 remain unclear in the intestinal epithelium. Methods The intestinal epithelial responses induced by IL-17 was evaluated using the human small intestinal organoid (enteroid) model. Results Organoid-forming efficiency, cell viability and proliferation of enteroids were decreased in proportion to the concentration of IL-17, which did not differ between the enteroids derived from controls and patients with Crohn’s disease. Bulk RNA-sequencing revealed the enrichment of secretion signaling in IL17-treated enteroids. Among its components, PIGR was up-regulated significantly as the concentration of IL-17 increased, resulting in IgA transcytosis and protective role against pathogens. The IL-17-induced cytotoxicity was predominantly mediated by pyroptosis with activation of CASP1 and cleavage of GSDMD. Single-cell RNA- sequencing identified pyroptosis occurred actively in intestinal stem cells (ISCs) and enterocytes. Anti-IL-17 antibody, izekizumab, completely restored IL-17-induced cytotoxicity, but suppressed mucin secretion and IgA transcytosis. CASP1 inhibitor, Ac-YVAD-cmk, restores cytotoxicity induced by IL-17, without impairing its beneficial effects. Conclusion IL-17 induces pyroptosis of ISCs and enterocytes, as well as mucin secretion and PIGR-induced IgA transcytosis. Paradoxical gastrointestinal effects of IL-17 neutralizing antibodies may be associated with inhibition of mucin secretion and IgA transcytosis. The inhibition of pyroptosis using the CASP1 inhibitor prevents the cytotoxicity induced by IL-17 without compromising its beneficial effects.