title: Polymerase Chain Reaction-Electrospray-Time-of-Flight Mass Spectrometry Versus Culture for Bacterial Detection in Septic Arthritis and Osteoarthritis.
abstract: BACKGROUND
  Preliminary studies have identified known bacterial pathogens in the knees of patients with osteoarthritis (OA) before arthroplasty.
  
  
  OBJECTIVE
  The current study was designed to determine the incidence and types of bacteria present in the synovial fluid of native knee joints from adult patients with diagnoses of septic arthritis and OA.
  
  
  METHODS
  Patients were enrolled between October 2010 and January 2013. Synovial fluid samples from the affected knee were collected and evaluated with both traditional microbial culture and polymerase chain reaction-electrospray ionization-time-of-flight mass spectrometry (molecular diagnostics [MDx]) to prospectively characterize the microbial content. Patients were grouped by diagnosis into one of two cohorts, those with clinical suspicion of septic arthritis (n = 44) and those undergoing primary arthroplasty of the knee for OA (n = 21). In all cases where discrepant culture and MDx results were obtained, we performed species-specific 16S rRNA fluorescence in situ hybridization (FISH) as a confirmatory test.
  
  
  RESULTS
  MDx testing identified bacteria in 50% of the suspected septic arthritis cases and 29% of the arthroplasty cases, whereas culture detected bacteria in only 16% of the former and 0% of the latter group. The overall difference in detection rates for culture and MDx was very highly significant, p-value = 2.384 × 10-7. All of the culture-positive cases were typed as Staphylococcus aureus. Two of the septic arthritis cases were polymicrobial as was one of the OA cases by MDx. FISH testing of the specimens with discordant results supported the MDx findings in 91% (19/21) of the cases, including one case where culture detected S. aureus and MDx detected Streptococcus agalactiae.
  
  
  CONCLUSIONS
  MDx were more sensitive than culture, as confirmed by FISH. FISH only identifies bacteria that are embedded or infiltrated within the tissue and is thus not susceptible to contamination. Not all suspected cases of septic arthritis contain bacteria, but a significant percent of patients with OA, and no signs of infection, have FISH-confirmed bacterial biofilms present in the knee.
authors.affiliation: 1 88th Surgical Operations Squadron, Orthopedic Surgery , Wright-Patterson Airforce Base, Dayton, Ohio.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Palmer
authors.affiliation: 2 Center of Excellence in Biofilm Research , Allegheny Health Network, Pittsburgh, Pennsylvania.
authors.forename: Rachael
authors.initials: R
authors.lastname: Melton-Kreft
authors.affiliation: 2 Center of Excellence in Biofilm Research , Allegheny Health Network, Pittsburgh, Pennsylvania.
authors.forename: Laura
authors.initials: L
authors.lastname: Nistico
authors.affiliation: 3 Department of Biological Sciences, Carnegie Mellon University , Pittsburgh, Pennsylvania.
authors.forename: N Louisa
authors.initials: NL
authors.lastname: Hiller
authors.affiliation: 3 Department of Biological Sciences, Carnegie Mellon University , Pittsburgh, Pennsylvania.
authors.forename: Leon H J
authors.initials: LH
authors.lastname: Kim
authors.affiliation: 4 Department of Orthopaedic Surgery, Allegheny General Hospital , Pittsburgh, Pennsylvania.
authors.forename: Gregory T
authors.initials: GT
authors.lastname: Altman
authors.affiliation: 4 Department of Orthopaedic Surgery, Allegheny General Hospital , Pittsburgh, Pennsylvania.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Altman
authors.affiliation: 4 Department of Orthopaedic Surgery, Allegheny General Hospital , Pittsburgh, Pennsylvania.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Sotereanos
authors.affiliation: 5 Institute for Molecular Medicine and Infectious Disease, Center for Genomic Sciences, Drexel University College of Medicine , Philadelphia, Pennsylvania.
authors.forename: Fen Z
authors.initials: FZ
authors.lastname: Hu
authors.affiliation: 4 Department of Orthopaedic Surgery, Allegheny General Hospital , Pittsburgh, Pennsylvania.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: De Meo
authors.affiliation: 5 Institute for Molecular Medicine and Infectious Disease, Center for Genomic Sciences, Drexel University College of Medicine , Philadelphia, Pennsylvania.|6 Institute for Molecular Medicine and Infectious Disease, Center for Advanced Microbial Processing, Drexel University College of Medicine , Philadelphia, Pennsylvania.|7 Department of Microbiology and Immunology, Drexel University College of Medicine , Philadelphia, Pennsylvania.|8 Department of Otolaryngology-Head and Neck Surgery, Drexel University College of Medicine , Philadelphia, Pennsylvania.
authors.forename: Garth D
authors.initials: GD
authors.lastname: Ehrlich
mesh_terms: D000328:Adult; D001170:Arthritis, Infectious / Q000175:diagnosis / Q000382:microbiology*; D015373:Bacterial Typing Techniques / Q000379:methods; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D025202:Molecular Diagnostic Techniques / Q000379:methods; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013211:Staphylococcus aureus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D013582:Synovial Fluid / Q000382:microbiology
chemical_list: D012336:RNA, Ribosomal, 16S
keywords: bacterial infection; fluorescent in situ hybridization; molecular diagnostics; osteoarthritis; septic arthritis