title: Role and antimicrobial resistance of staphylococci involved in prosthetic joint infections.
abstract: OBJECTIVE
  Staphylococci are responsible for approximately half of all prosthetic joint infections (PJIs) and they are often multi-drug resistant. The main purpose of this study was to evaluate the incidence of PJIs caused by staphylococci in our hospital from March 2010 to February 2012, with particular reference to antibiotic resistance in relation to their classification as contaminant or infecting isolates.
  
  
  METHODS
  We analyzed samples recovered from 124 patients: most of them were male (55.8%) and the mean age was 66 ± 14 years. Prostheses derived from hip (54.8%) or knee (45.2%) replacement and they were processed by sonication. Isolates were identified using conventional biochemical methodologies. Antimicrobial susceptibility testing was carried out using the disk diffusion method as described by the European Committee on Antimicrobial Susceptibility Testing.
  
  
  RESULTS
  A total of 135 staphylococci were isolated: the prevalent species was Staphylococcus aureus, but, on the whole, coagulase-negative staphylococci represented 57% of cases. Fifty-one isolates were recovered from a single sample and were therefore defined as contaminant. Linezolid and glycopeptides showed excellent activity versus all the tested isolates, while penicillin, levofloxacin, and erythromycin offered reduced activity against staphylococci. Interestingly, high resistance rates were observed for coagulase-negative staphylococci other than S. epidermidis classified as contaminant strains.
  
  
  CONCLUSIONS
  We observed a remarkable spread of coagulase-negative staphylococci as causative agents of PJIs; but most of them were classified as contaminants. However, because of their low susceptibility to the antibiotics tested, further studies are necessary to evaluate their role as pathogens or as true contaminants.
authors: 2 Laboratory of Medical Technical Sciences, Department of Biomedical Sciences for Health, University of Milan, Sacco Hospital, Milan - Italy.
authors: Lorenzo
authors: L
authors: Drago
authors: Elena
authors: E
authors: De Vecchi
authors: Laura
authors: L
authors: Cappelletti
authors: Roberto
authors: R
authors: Mattina
authors: Christian
authors: C
authors: Vassena
authors: Carlo L
authors: CL
authors: Romanò
mesh_terms: D000328:Adult; D000368:Aged; D000890:Anti-Infective Agents / Q000627:therapeutic use*; D004352:Drug Resistance, Microbial; D005260:Female; D006622:Hip Prosthesis / Q000009:adverse effects* / Q000382:microbiology; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects* / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D016459:Prosthesis-Related Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000209:etiology; D013210:Staphylococcus / Q000145:classification / Q000302:isolation & purification*
chemical_list: D000890:Anti-Infective Agents