title: In vivo and in vitro demonstration that Staphylococcus aureus is an intracellular pathogen in the presence or absence of fibronectin-binding proteins.
abstract: Staphylococcus aureus is the most significant bacterial pathogen associated with bovine mastitis. However, the relevance of intracellular infection to mastitis pathogenesis is poorly understood. We used in vitro assays and a mouse model of mastitis to demonstrate the intracellular component of the infection and to identify the importance of fibronectin-binding proteins in the processes of colonization and internalization. In vitro, a mutant strain, lacking fibronectin-binding protein (FnBPs(-)), had a reduced ability to bind fibronectin and to infect epithelial cells when compared to its parental wild type strain. After 2 h of infection, the internalization of the mutant bacteria into epithelial cell cultures was reduced by 60% compared with the wild type. After in vivo infection, microscopic examination using the FnBPs(-) strain revealed that production of a high density of live bacteria within the mammary gland epithelial cells was delayed. Both parental and mutant strains were identified within neutrophils, macrophages and epithelial cells suggesting a close similarity between the mouse mastitis model and bovine mastitis. These results demonstrate that S. aureus was able to cause an intracellular infection in the mouse model of mastitis and that the elimination of one adhesion protein delayed, but did not prevent, infection.
authors.affiliation: Centre d'Etude et de Valorisation de la Diversité Microbienne, Département de Biologie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Qué., Canada J1K 2R1.
authors.forename: Eric
authors.initials: E
authors.lastname: Brouillette
authors.forename: Gilles
authors.initials: G
authors.lastname: Grondin
authors.forename: Lulzim
authors.initials: L
authors.lastname: Shkreta
authors.forename: Pierre
authors.initials: P
authors.lastname: Lacasse
authors.forename: Brian G
authors.initials: BG
authors.lastname: Talbot
mesh_terms: D018829:Adhesins, Bacterial; D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D015169:Colony Count, Microbial; D003593:Cytoplasm / Q000382:microbiology*; D004847:Epithelial Cells / Q000166:cytology / Q000382:microbiology*; D005353:Fibronectins / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000382:microbiology; D008321:Mammary Glands, Animal / Q000166:cytology / Q000382:microbiology*; D008413:Mastitis / Q000382:microbiology; D051379:Mice; D008853:Microscopy; D008854:Microscopy, Electron; D016254:Mutagenesis, Insertional; D009504:Neutrophils / Q000166:cytology / Q000382:microbiology; D013203:Staphylococcal Infections / Q000382:microbiology / Q000662:veterinary; D013211:Staphylococcus aureus / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; D005353:Fibronectins; C078635:fibronectin-binding proteins, bacterial