title: stg fimbrial operon from S. Typhi STH2370 contributes to association and cell disruption of epithelial and macrophage-like cells.
abstract: BACKGROUND
  Salmonella enterica serovar Typhi (S. Typhi) stg operon, encoding a chaperone/usher fimbria (CU), contributes to an increased adherence to human epithelial cells. However, one report suggests that the presence of the Stg fimbria impairs the monocyte--bacteria association, as deduced by the lower level of invasion to macrophage-like cells observed when the stg fimbrial cluster was overexpressed. Nevertheless, since other CU fimbrial structures increase the entry of S. Typhi into macrophages, and considering that transcriptomic analyses revealed that stg operon is indeed expressed in macrophages, we reassessed the role of the stg operon in the interaction between S. Typhi strain STH2370 and human cells, including macrophage-like cells and mononuclear cells directly taken from human peripheral blood.
  
  
  RESULTS
  We compared S. Typhi STH2370 WT, a Chilean clinical strain, and the S. Typhi STH2370 Δstg mutant with respect to association and invasion using epithelial and macrophage-like cells. We observed that deletion of stg operon reduced the association and invasion of S. Typhi, in both cellular types. The presence of the cloned stg operon restored the WT phenotype in all the cases. Moreover, we compared Salmonella enterica sv. Typhimurium 14028s (S. Typhimurium, a serovar lacking stg operon) and S. Typhimurium heterologously expressing S. Typhi stg. We found that the latter presents an increased cell disruption of polarized epithelial cells and an increased association in both epithelial and macrophage-like cells.
  
  
  CONCLUSIONS
  S. Typhi stg operon encodes a functional adhesin that participates in the interaction bacteria-eukaryotic cells, including epithelial cells and macrophages-like cells. The phenotypes associated to stg operon include increased association and consequent invasion in bacteria-eukaryotic cells, and cell disruption.
authors.affiliation: Laboratorio de Microbiología, Facultad de Ciencias Biológicas, Universidad Andres Bello, República 217, Santiago, Chile. lberrocal@uft.cl.|Escuela de Medicina, Facultad de Medicina, Universidad Finis Terrae, Santiago, Av. Pedro de Valdivia 1509, Providencia, Santiago, Chile. lberrocal@uft.cl.
authors.forename: Liliana
authors.initials: L
authors.lastname: Berrocal
authors.affiliation: Laboratorio de Microbiología, Facultad de Ciencias Biológicas, Universidad Andres Bello, República 217, Santiago, Chile. jfuentes@unab.cl.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Fuentes
authors.affiliation: Laboratorio de Microbiología, Facultad de Ciencias Biológicas, Universidad Andres Bello, República 217, Santiago, Chile. annette.trombert@umayor.cl.|Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Camino La Pirámide 5750, Huechuraba, Santiago, Chile. annette.trombert@umayor.cl.
authors.forename: A Nicole
authors.initials: AN
authors.lastname: Trombert
authors.affiliation: Laboratorio de Microbiología, Facultad de Ciencias Biológicas, Universidad Andres Bello, República 217, Santiago, Chile. mjofreb@uft.cl.|Escuela de Medicina, Facultad de Medicina, Universidad Finis Terrae, Santiago, Av. Pedro de Valdivia 1509, Providencia, Santiago, Chile. mjofreb@uft.cl.
authors.forename: Matías R
authors.initials: MR
authors.lastname: Jofré
authors.affiliation: Laboratorio de Microbiología, Facultad de Medicina, Universidad Andres Bello, República 313, Santiago, Chile. villagra@unab.cl.
authors.forename: Nicolás A
authors.initials: NA
authors.lastname: Villagra
authors.affiliation: Laboratorio de Microbiología, Facultad de Ciencias Biológicas, Universidad Andres Bello, República 217, Santiago, Chile. lu.valenzuela.v@uandresbello.edu.
authors.forename: Luis M
authors.initials: LM
authors.lastname: Valenzuela
authors.affiliation: Laboratorio de Microbiología, Facultad de Medicina, Universidad Andres Bello, República 313, Santiago, Chile. gmora@unab.cl.
authors.forename: Guido C
authors.initials: GC
authors.lastname: Mora
mesh_terms: D002448:Cell Adhesion; D004847:Epithelial Cells / Q000382:microbiology*; D010861:Fimbriae, Bacterial / Q000235:genetics* / Q000502:physiology; D006801:Humans; D008264:Macrophages / Q000382:microbiology*; D009876:Operon / Q000235:genetics* / Q000502:physiology*; D012485:Salmonella typhi / Q000235:genetics* / Q000502:physiology