title: Delta-toxin production deficiency in Staphylococcus aureus: a diagnostic marker of bone and joint infection chronicity linked with osteoblast invasion and biofilm formation.
abstract: Biofilm formation, intra-osteoblastic persistence, small-colony variants (SCVs) and the dysregulation of agr, the major virulence regulon, are possibly involved in staphylococcal bone and joint infection (BJI) pathogenesis. We aimed to investigate the contributions of these mechanisms among a collection of 95 Staphylococcus aureus clinical isolates from 64 acute (67.4%) and 31 chronic (32.6%) first episodes of BJI. The included isolates were compared for internalization rate, cell damage and SCV intracellular emergence using an ex vivo model of human osteoblast infection. Biofilm formation was assessed in a microbead immobilization assay (BioFilm Ring test). Virulence gene profiles were assessed by DNA microarray. Seventeen different clonal complexes were identified among the screened collection. The staphylococcal internalization rate in osteoblasts was significantly higher for chronic than acute BJI isolates, regardless of the genetic background. Conversely, no differences regarding cytotoxicity, SCV emergence, biofilm formation and virulence gene distribution were observed. Additionally, agr dysfunction, detected by the lack of delta-toxin production using whole-cell matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) analysis (n = 15; 15.8%), was significantly associated with BJI chronicity, osteoblast invasion and biofilm formation. These findings provide new insights into MSSA BJI pathogenesis, suggesting the correlation between chronicity and staphylococcal osteoblast invasion. This adaptive mechanism, along with biofilm formation, is associated with agr dysfunction, which can be routinely assessed by delta-toxin detection using MALDI-TOF spectrum analysis, possibly providing clinicians with a diagnostic marker of BJI chronicity at the time of diagnosis.
authors: Department of Infectious Diseases, Hospices Civils de Lyon, France; Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, France; INSERM U1111, International Centre for Infectiology Research, France; Claude Bernard Lyon 1 University, France. Electronic address: florent.valour@chu-lyon.fr.
authors: F
authors: F
authors: Valour
authors: Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, France; INSERM U1111, International Centre for Infectiology Research, France; Claude Bernard Lyon 1 University, France.
authors: J-P
authors: JP
authors: Rasigade
authors: INSERM U1111, International Centre for Infectiology Research, France.
authors: S
authors: S
authors: Trouillet-Assant
authors: Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, France.
authors: J
authors: J
authors: Gagnaire
authors: Department of Infectious Diseases, Hospices Civils de Lyon, France.
authors: A
authors: A
authors: Bouaziz
authors: Department of Infectious Diseases, Hospices Civils de Lyon, France.
authors: J
authors: J
authors: Karsenty
authors: Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, France.
authors: C
authors: C
authors: Lacour
authors: Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, France; INSERM U1111, International Centre for Infectiology Research, France.
authors: M
authors: M
authors: Bes
authors: INSERM U1111, International Centre for Infectiology Research, France; Claude Bernard Lyon 1 University, France; Orthopaedic Surgery department, Hospices Civils de Lyon, France.
authors: S
authors: S
authors: Lustig
authors: Department of Infection Control and Epidemiology, Hospices Civils de Lyon, Edouard Herriot Hospital, Lyon, France.
authors: T
authors: T
authors: Bénet
authors: Department of Infectious Diseases, Hospices Civils de Lyon, France; INSERM U1111, International Centre for Infectiology Research, France; Claude Bernard Lyon 1 University, France.
authors: C
authors: C
authors: Chidiac
authors: Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, France; INSERM U1111, International Centre for Infectiology Research, France; Claude Bernard Lyon 1 University, France.
authors: J
authors: J
authors: Etienne
authors: Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, France; INSERM U1111, International Centre for Infectiology Research, France; Claude Bernard Lyon 1 University, France.
authors: F
authors: F
authors: Vandenesch
authors: Department of Infectious Diseases, Hospices Civils de Lyon, France; INSERM U1111, International Centre for Infectiology Research, France; Claude Bernard Lyon 1 University, France.
authors: T
authors: T
authors: Ferry
authors: Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, France; INSERM U1111, International Centre for Infectiology Research, France; Claude Bernard Lyon 1 University, France.
authors: F
authors: F
authors: Laurent
mesh_terms: D001427:Bacterial Toxins / Q000032:analysis*; D018441:Biofilms / Q000254:growth & development*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000382:microbiology*; D010006:Osteoblasts / Q000382:microbiology*; D012189:Retrospective Studies; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification* / Q000502:physiology
chemical_list: D001427:Bacterial Toxins; C025971:staphylococcal delta toxin
keywords: Biofilm formation; Staphylococcus aureus; bone and joint infection; delta-toxin; matrix-assisted laser desorption ionization time-of-flight mass spectrometry; osteoblast invasion