title: Epidemiology and Antibiotic Resistance of Late Prosthetic Knee and Hip Infections.
abstract: Prosthetic joint infections (PJI) are still a major complication of hip and knee arthroplasties. Identification of the causative pathogens and knowledge of their antibiotic susceptibilities are essential for the management of these infections. The main purpose of the study was to identify and compare the causative bacteria of prosthetic knee and hip joint infections in a reference Italian orthopedic center and to characterize antibiotic resistance profiles of bacteria involved.
  
  
  
  Data from 429 patients with diagnosis of PJI were collected from January 2013 to June 2015: 229 presented a hip and 200 a knee prosthesis infection. Prostheses and periprosthetic tissues were treated with dithiothreitol before plating onto different media and broths. Identification and antimicrobial susceptibility testing were carried out by VITEK2 Compact (bioMerieux).
  
  
  
  There was not a substantial difference in the etiology of hip and knee PJI: staphylococci were the most frequently isolated bacteria in both groups, followed by Enterobacteriaceae and Propionibacterium acnes. Staphylococci showed a high rate of methicillin resistance (144 of 341) and a worrying frequency of isolates were resistant to teicoplanin (9%). Only 8.3% of Enterobacteriaceae produced extended-spectrum beta-lactamases, whereas the rate of carbapenemase-producing bacteria was not significant.
  
  
  
  We observed similar etiology of hip and knee PJIs. Nevertheless, bacteria isolated from knee showed higher resistance rates to glycopeptides and fluoroquinolones when compared with those isolated from the hip. The reason for this difference remains to be elucidated in future studies.
authors.affiliation: Laboratory of Clinical Chemistry and Microbiology, IRCCS Galeazzi Orthopedic Institute, Milan, Italy; Laboratory of Clinical Microbiology, Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Drago
authors.affiliation: Laboratory of Clinical Chemistry and Microbiology, IRCCS Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: De Vecchi
authors.affiliation: Laboratory of Clinical Chemistry and Microbiology, IRCCS Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Bortolin
authors.affiliation: Hip Surgery, IRCCS Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Zagra
authors.affiliation: Centre for Reconstructive Surgery and Bone and Joint Infections, IRCCS Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Carlo L
authors.initials: CL
authors.lastname: Romanò
authors.affiliation: Laboratory of Clinical Chemistry and Microbiology, IRCCS Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Cappelletti
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects; D001426:Bacterial Proteins / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D005260:Female; D006621:Hip Joint / Q000601:surgery*; D006801:Humans; D007717:Knee; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis / Q000382:microbiology*; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D016459:Prosthesis-Related Infections / Q000453:epidemiology*; D055815:Young Adult; D001618:beta-Lactamases / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D001618:beta-Lactamases; C063912:carbapenemase
keywords: epidemiology; hip; infections; knee; prostheses