The SPI-19 encoded type-six secretion-systems (T6SS) of Salmonella enterica serovars Gallinarum and Dublin play different roles during infection

Abstract

Salmonella Pathogenicity Islands 19 (SPI19) encodes a type VI secretion system (T6SS). SPI19 is only present in few serovars of S. enterica, including the host-adapted serovar S. Dublin and the host-specific serovar S. Gallinarum. The role of the SPI19 encoded T6SS in virulence in these serovar is not fully understood. Here we show that during infection of mice, a SPI19/T6SS deleted strain of S. Dublin 2229 was less virulent than the wild type strain after oral challenge, but not after IP challenge. The mutant strain also competed significantly poorer than the wild type strain when co-cultured with strains of E. coli, suggesting that this T6SS plays a role in pathogenicity by killing competing bacteria in the intestine. No significant difference was found between wild type S.Gallinarum G9 and its SPI19/T6SS mutant in infection, whether chicken were challenged orally or by the IP route, and the S. Gallinarum G9 SPI19/T6SS strain competed equally well as the wild type strain against strains of E. coli. However, contrary to what was observed with S. Dublin, the wild type G9 strains was significantly more cytotoxic to monocyte derived primary macrophages from hens than the mutant, suggesting that SPI19/T6SS in S. Gallinarum mediates killing of eukaryotic cells. The lack of significant importance of SPI19/T6SS after oral and systemic challenge of chicken was confirmed by knocking out SPI19 in a second strain, J91. Together the results suggest that the T6SS encoded from SPI19 have different roles in the two serovars and that it is a virulence-factor after oral challenge of mice in S. Dublin, while we cannot confirm previous results that SPI19/T6SS influence virulence significantly in S. Gallinarum.

Genomic Analysis of Antimicrobial Resistance and Resistance Plasmids in Salmonella Serovars from Poultry in Nigeria

“…T6SS systems in Salmonella are encoded from the horizontally acquired islands, SPI-6 or SPI-19 [60,61]. Reports have demonstrated that T6SS plays a role in Salmonella pathogenicity; SPI-19 plays a role in killing competing bacteria in the intestine [61,62], and it would be interesting to investigate the role of T6SS in S. Muenster, S. Chester and S. Aberdeen. Interestingly, three S. Isangi, S. Takoradi and S. Larochelle strains were identified to have virulence genes not possessed by the other strains in our study; virulence genes that have not been reported in these serotypes previously.…”

Embracing Diversity: Differences in Virulence Mechanisms, Disease Severity, and Host Adaptations Contribute to the Success of Nontyphoidal Salmonella as a Foodborne Pathogen

“…Like other serovars that are frequently associated with invasive human disease, S . Choleraesuis encodes a T6SS, which plays a role in virulence in vivo (Schroll et al, 2019). S .…”

Bacteriophage-Insensitive Mutants of Antimicrobial-Resistant Salmonella Enterica are Altered in their Tetracycline Resistance and Virulence in Caco-2 Intestinal Cells

“…Variant analysis revealed several mutations in components involved in the Type VI secretion system (T6SS) of SPI-19 that plays a role in intestinal infection (Table 1) [39][40][41]. Homology between the contractile components of phages and T6SS of several Salmonella serovars that deliver cytotoxic effector proteins via spikes that enter the host cell was recently reported [42][43][44]. Many core structural components, however, have not been extensively characterized on a functional level [45].…”