title: Infection mechanism of biofilm-forming Staphylococcus aureus on indwelling foreign materials in mice.
abstract: Indwelling foreign-body infections are a critical medical problem, especially in immunocompromised patients. To examine the pathogenicity of biofilm-forming bacteria settling on foreign materials, mice implanted with plastic discs were infected with Staphylococcus aureus. After opening a wide subcutaneous pocket on the dorsal side of mice with or without temporal leukocytopenia, a plastic sheet was placed in the left subcutaneous space; subsequently, bacteria in a planktonic state were dispersed over the subcutaneous space. Bacterial numbers were examined 7 days after inoculation. In subcutaneous tissue on the right, S. aureus was found only in leukocytopenic mice. Meanwhile, bacteria were detected on the plastic and neighbouring tissue in both leukocytopenic and normal mice; however, colony-forming analysis indicated that leukocytopenic mice possessed significantly more bacteria. Tissue reaction against bacteria was pathologically examined. Invading S. aureus induced severe inflammation. In transient leukocytopenic mice, bacterial microcolonies formed on the plastic as well as in the developed necrotic tissue - both of which were shielded from inflammatory cell infiltration - result in bacteraemia. These results indicate that biofilm-forming S. aureus settling on indwelling foreign material are tolerant against host immunity and assault neighbouring tissue, which may lead to chronic wound infection.
authors.affiliation: Department of Plastic, Reconstructive and Aesthetic Surgery, Fukuoka University, Fukuoka, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Makino
authors.forename: Shiro
authors.initials: S
authors.lastname: Jimi
authors.forename: Takuto
authors.initials: T
authors.lastname: Oyama
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nakano
authors.forename: Kouichi
authors.initials: K
authors.lastname: Hamamoto
authors.forename: Kanako
authors.initials: K
authors.lastname: Mamishin
authors.forename: Tomoko
authors.initials: T
authors.lastname: Yahiro
authors.forename: Shuuji
authors.initials: S
authors.lastname: Hara
authors.forename: Tohru
authors.initials: T
authors.lastname: Takata
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohjimi
mesh_terms: D000818:Animals; D018441:Biofilms; D004195:Disease Models, Animal; D005260:Female; D005547:Foreign Bodies / Q000382:microbiology* / Q000473:pathology; D007970:Leukopenia / Q000150:complications / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D013203:Staphylococcal Infections / Q000209:etiology* / Q000473:pathology; D013211:Staphylococcus aureus / Q000502:physiology*; D014946:Wound Infection / Q000209:etiology* / Q000473:pathology
keywords: Biofilm; Foreign materials; Immunosuppression; Mice; Staphylococcus aureus