Summary
This study identified trends in microorganism and antibiotic resistance profile in both early and late PJIs to guide empiric antibiotics selection.
Abstract
Introduction
Understanding the causative microorganisms and initiating early appropriate empirical antibiotics is important in the management of periprosthetic joint infections (PJI). This study identified trends in microorganism and antibiotic resistance profile in both early and late PJIs to guide empiric antibiotics selection.
Methods
Five-hundred and thirty-nine first-episode PJIs following primary TKA at three tertiary hospitals between 2000-2023 were included. PJIs were classified using the Auckland classification into early (<1 year since primary) and late (>1 year since primary) PJIs. For each case, the causative organism(s) and antibiotic sensitivity were recorded and analysed.
Results
From 487 PJI cases, 606 cultures were included. Early (<1 year) PJIs were more likely to involve resistant microorganisms (OR 2.85, CI 1.71 – 4.76, P<0.05) and be polymicrobial (OR 8.714, CI 3.95 – 19.22, P<0.05). The predominant organisms for both early and late PJIs was Staphylococci Aureus, 33% and 32%, respectively. Gram-negative microorganisms contributed to 20% of cases in both early and late PJIs. Flucloxacillin monotherapy provided sufficient coverage for 54% of early PJI cases and 74% of late PJI cases. In comparison, Vancomycin monotherapy provided sufficient coverage of 82% in both early and late PJI cases, while the addition of a gram negative antibiotic increased overage to over 90%. The number of resistant cases remained unchanged across the 23-year period, involving approximately 1 in 6 PJIs (p>0.05).
Conclusion
Despite the emergence of resistant organisms in healthcare settings, the primary causative microorganisms have remained the same in knee PJIs with no notable increase in resistance cases over the past two decades. In early PJIs, initial empiric antibiotic coverage using vancomycin and a gram-negative agent would optimise coverage.