Differential roles for pathogenicity islands SPI-13 and SPI-8 in the interaction of Salmonella Enteritidis and Salmonella Typhi with murine and human macrophages.
BACKGROUND
Salmonella pathogenicity island (SPI)-13 is conserved in many serovars of S. enterica, including S. Enteritidis, S. Typhimurium and S. Gallinarum. However, it is absent in typhoid serovars such as S. Typhi and Paratyphi A, which carry SPI-8 at the same genomic location. Because the interaction with macrophages is a critical step in Salmonella pathogenicity, in this study we investigated the role played by SPI-13 and SPI-8 in the interaction of S. Enteritidis and S. Typhi with cultured murine (RAW264.7) and human (THP-1) macrophages.


RESULTS
Our results showed that SPI-13 was required for internalization of S. Enteritidis in murine but not human macrophages. On the other hand, SPI-8 was not required for the interaction of S. Typhi with human or murine macrophages. Of note, the presence of an intact copy of SPI-13 in a S. Typhi mutant carrying a deletion of SPI-8 did not improve its ability to be internalized by, or survive in human or murine macrophages.


CONCLUSIONS
Altogether, our results point out to different roles for SPI-13 and SPI-8 during Salmonella infection. While SPI-13 contributes to the interaction of S. Enteritidis with murine macrophages, SPI-8 is not required in the interaction of S. Typhi with murine or human macrophages. We hypothesized that typhoid serovars have lost SPI-13 and maintained SPI-8 to improve their fitness during another phase of human infection.
['Espinoza|Rodrigo A|RA|', 'Silva-Valenzuela|Cecilia A|CA|', 'Amaya|Fernando A|FA|', 'Urrutia|Ítalo M|ÍM|', 'Contreras|Inés|I|', 'Santiviago|Carlos A|CA|']
D000704:Analysis of Variance D000818:Animals D018407:Bacterial Physiological Phenomena D002470:Cell Survival D002478:Cells, Cultured D016680:Genome, Bacterial D044404:Genomic Islands D006801:Humans D008264:Macrophages D051379:Mice D056265:Microbial Interactions D009115:Muridae D016133:Polymerase Chain Reaction D000067996:RAW 264.7 Cells D012480:Salmonella Infections D012477:Salmonella enteritidis D012485:Salmonella typhi D065288:Serogroup D013045:Species Specificity
SPI-13 SPI-8 Salmonella Enteritidis Typhi Macrophages RAW264.7 THP-1