title: Following pathogen development and gene expression in a food ecosystem: the case of a Staphylococcus aureus isolate in cheese.
abstract: Human intoxication or infection due to bacterial food contamination constitutes an economic challenge and a public health problem. Information on the in situ distribution and expression of pathogens responsible for this risk is to date lacking, largely because of technical bottlenecks in detecting signals from minority bacterial populations within a complex microbial and physicochemical ecosystem. We simulated the contamination of a real high-risk cheese with a natural food isolate of Staphylococcus aureus, an enterotoxin-producing pathogen responsible for food poisoning. To overcome the problem of a detection limit in a solid matrix, we chose to work with a fluorescent reporter (superfolder green fluorescent protein) that would allow spatiotemporal monitoring of S. aureus populations and targeted gene expression. The combination of complementary techniques revealed that S. aureus localizes preferentially on the cheese surface during ripening. Immunochemistry and confocal laser scanning microscopy enabled us to visualize, in a single image, dairy bacteria and pathogen populations, virulence gene expression, and the toxin produced. This procedure is readily applicable to other genes of interest, other bacteria, and different types of food matrices.
authors.affiliation: INRA, UMR 1319 Micalis, AgroParisTech, Jouy-en-Josas, France isabelle.fleurot@jouy.inra.fr.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Fleurot
authors.affiliation: INRA, UMR 1319 Micalis, AgroParisTech, Jouy-en-Josas, France.
authors.forename: Marina
authors.initials: M
authors.lastname: Aigle
authors.affiliation: INRA, UMR 1198 BDR, Jouy-en-Josas, France.
authors.forename: Renaud
authors.initials: R
authors.lastname: Fleurot
authors.affiliation: INRA, UMR 1319 Micalis, AgroParisTech, Jouy-en-Josas, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Darrigo
authors.affiliation: Université Paris-Est, Anses, Laboratoire de sécurité des aliments de Maisons-Alfort, Unité SBCL, Maisons-Alfort, France.
authors.forename: Jacques-Antoine
authors.initials: JA
authors.lastname: Hennekinne
authors.affiliation: INRA, UMR 1319 Micalis, AgroParisTech, Jouy-en-Josas, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Gruss
authors.affiliation: INRA, UMR 1319 Micalis, AgroParisTech, Jouy-en-Josas, France.
authors.forename: Elise
authors.initials: E
authors.lastname: Borezée-Durant
authors.affiliation: INRA, UMR 1319 Micalis, AgroParisTech, Jouy-en-Josas, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Delacroix-Buchet
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002611:Cheese / Q000382:microbiology*; D017753:Ecosystem; D004768:Enterotoxins / Q000378:metabolism; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006801:Humans; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004768:Enterotoxins