A ROD9 island encoded gene in Salmonella Enteritidis plays an important role in acid tolerance response and helps in systemic infection in mice

Abstract

Salmonella, like other pathogenic bacteria has undergone multiple genomic alterations to adapt itself into specific host environments executing varied degrees of virulence through evolution. Such variations in genome content have been assumed to lead the closely related non-typhoidal serovars, S. Enteritidis, and S. Typhimurium to exhibit Type Three Secretion System −2 (T3SS-2) based diverse colonization and inflammation kinetics. Mutually exclusive genes present in either of the serovars are recently being studied and in our currentwork, we focused on a particular island ROD9, present in S. Enteritidis but not in S. Typhimurium. Earlier reports have identified a few genes from this island to be responsible for virulence in vitro as well as in vivo. In this study, we have identified another gene, SEN1008 from the same island encoding a hypothetical protein to be a potential virulence determinant showing systemic attenuation upon mutation in C57BL/6 mice infection model. The isogenic mutant strain displayed reduced adhesion to epithelial cells in vitro as well as was highly immotile. It was also deficient in intracellular replication in vitro, with a highly suppressed SPI-2and failed to cause acute colitis at 72-h p.i.in vivo. Moreover, on acid exposure, SEN1008 showed 17 folds and 2 fold up-regulations during adaptation and challenge phases,respectively and ΔSEN1008 failed to survive during ATR assay, indicating its role under acid stress. Together, our findings suggested ΔSEN1008 to be significantly attenuated and we propose this gene to be a potent factor responsible for S. Enteritidis pathogenesis.

Genome-wide fitness analysis identifies genes required for in vitro growth and macrophage infection by African and Global Epidemic pathovariants of Salmonella Enteritidis

“…Three genes only present in P125109 were also identified as “macrophage-specific”, namely SEN0912 (encoding a hypothetical protein) and two tRNA genes ( tRNA-Ala and tRNA-Thr ). No genes from the ROD9 region were identified, despite reports that ROD9-associated genes played a role in virulence in macrophage and animal infection [16, 20, 69]. Based on COG classifications, the majority of the 177 “macrophage-specific” genes were associated with nucleotide transport and metabolism (F, 17%), amino acid transport and metabolism (E, 10%), transcription (K, 8%) and translation (J, 9%).…”

“…To generate non-polar, in-frame deletions of phoPQ, the corresponding Km-resistant derivatives were transformed with the temperature-sensitive pCP20-tet [41] (for P125109) or pCP20-Gm [42] (for D7795) plasmid that synthesises the FLP recombinase. Transformants were selected by overnight growth at 30°C on LB agar plates containing Tet 25 or Gm 20 , followed by passaging on LB agar plates at 37°C to cure the pCP20 plasmid. Loss of the antibiotic resistance cassette and pCP20 was confirmed by checking for loss of resistance to Km and Tet (or Gm).…”

“…To date, genome-wide functional analyses of S. Enteritidis focused on gastroenteritisassociated S. Enteritidis in several in vitro conditions as well as during interaction with human epithelial cells, avian macrophages, and an animal infection model [16][17][18][19]. Other approaches investigated the role of specific genomic regions such as Salmonella Pathogenicity Islands (SPIs) and Regions of Difference (RODs) [20][21][22][23]. However, there have been no previous functional genomic analyses of African S. Enteritidis.…”

Genome-wide fitness analysis identifies genes required for in vitro growth and macrophage infection by African and global epidemic pathovariants of Salmonella enterica Enteritidis

“… enterica Enteritidis in several in vitro conditions, as well as during interaction with human epithelial cells, avian macrophages and during mouse infection [17–20]. Other approaches investigated the role of specific genomic regions such as Salmonella pathogenicity islands (SPIs) and regions of difference (RODs) [21–24]. Research on bloodstream-infection-associated African Salmonella has been focused on the S .…”

“…To date, genome-wide functional analyses of S. enterica Enteritidis have focused on gastroenteritis-associated S. enterica Enteritidis in several in vitro conditions, as well as during interaction with human epithelial cells, avian macrophages and during mouse infection [17][18][19][20]. Other approaches investigated the role of specific genomic regions such as Salmonella pathogenicity islands (SPIs) and regions of difference (RODs) [21][22][23][24]. Research on bloodstream-infection-associated African Salmonella has been focused on the S. enterica Typhimurium serovar [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42].…”