The type VI secretion system encoded in Salmonella pathogenicity island 19 is required for Salmonella enterica serotype Gallinarum survival within infected macrophages
Authors: Francisca Contreras
Carlos J Blondel
David Pezoa
Juan C Jiménez
Lorenzo E Leiva
Sergio A Alvarez
Carlos A Santiviago
Inés Contreras
Bernardo I Pinto
Journal: Infection and Immunity (2013)
Discipline: IMMUNOLOGY
Keywords: Salmonella enterica serotype Gallinarum; fowl typhoid; type VI secretion system (T6SS); Salmonella pathogenicity island 19 (SPI-19); colonization
Affiliations: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile.

Abstract:  Salmonella enterica serotype Gallinarum is the causative agent of fowl typhoid, a disease characterized by high morbidity and mortality that causes major economic losses in poultry production. We have reported that S. Gallinarum harbors a type VI secretion system (T6SS) encoded in Salmonella pathogenicity island 19 (SPI-19) that is required for efficient colonization of chicks. In the present study, we aimed to characterize the SPI-19 T6SS functionality and to investigate the mechanisms behind the phenotypes previously observed in vivo. Expression analyses revealed that SPI-19 T6SS core components are expressed and produced under in vitro bacterial growth conditions. However, secretion of the structural/secreted components Hcp1, Hcp2, and VgrG to the culture medium could not be determined, suggesting that additional signals are required for T6SS-dependent secretion of these proteins. In vitro bacterial competition assays failed to demonstrate a role for SPI-19 T6SS in interbacterial killing. In contrast, cell culture experiments with murine and avian macrophages (RAW264.7 and HD11, respectively) revealed production of a green fluorescent protein-tagged version of VgrG soon after Salmonella uptake. Furthermore, infection of RAW264.7 and HD11 macrophages with deletion mutants of SPI-19 or strains with genes encoding specific T6SS core components (clpV and vgrG) revealed that SPI-19 T6SS contributes to S. Gallinarum survival within macrophages at 20 h postuptake. SPI-19 T6SS function was not linked to Salmonella-induced cytotoxicity or cell death of infected macrophages, as has been described for other T6SS. Our data indicate that SPI-19 T6SS corresponds to a novel tool used by Salmonella to survive within host cells. 

Retracted: No

PubPeer comments:
 September 2015 correction: https: iai.asm.org content 83 10 4175 It reads:  Page 1213: Figure 2 should appear as shown below. Here is the original Figure 2, with red and blue boxes marking possible duplicated panels. ![file] , 
 I thank the Journal and Dr. Bik for spotting this unintentional error while assembling this figure. The panels were indeed duplicated. We apologize for this mistake. Errors such as this should not happen and for us it was an attention call to increase the scientific rigor and standards to the highest level. I am attaching our report submitted to the Journal in 2015 that lead to the published correction with the correct panels. I strongly believe that the work done by the pubpeer community, Dr. Bik and others is of key importance in terms of accountability in our fields. At least, I know I am a better scientist now because of this episode. ![file] ![file] ![file] ,