Analysis of postoperative and hematogenous prosthetic joint-infection microbiological patterns in a large cohort.

Objectives: This study was undertaken to analyze prosthetic joint infection (PJI)-causing microorganisms and compare their distribution patterns according to PJI classification.

Methods: Cohort study from a single referral center for bone-and-joint infections from January 2004 to December 2015.

Results: Nine hundred and twenty-six patients, who developed 997 PJIs, involving the hip (62%), knee (35%) and/or shoulder (1%), were included. PJIs were classified as early postoperative (19%), late chronic (30%), hematogenous (35%) and undetermined (16%). Pathogens most frequently isolated from early-postoperative PJIs were staphylococci (57%), with 25% each Staphylococcus aureus or Staphylococcus epidermidis; 21% were polymicrobial and 10% Gram-negative rods. For late-chronic PJIs, the most frequent microbes were staphylococci (61%), predominantly S. epidermidis (35%); anaerobic bacteria were isolated from 15%; 11% were polymicrobial. Hematogenous PJIs were 99% monomicrobial. Although S. aureus was the most frequently isolated species (28%), streptococci were isolated slightly more often than staphylococci (39% vs. 36%). Among streptococci, group B streptococci were the most frequent (15%). The portal of entry was identified for 52% of hematogenous PJIs: 15% cutaneous, 11% dental, 9% gastrointestinal, 6% urinary, and 11% miscellaneous.

Conclusion: Although a wide variety of microorganisms was isolated from PJIs, specific microbiological patterns were observed according to infection classification.