According to a single-center retrospective study published in Infectious Diseases Now, positive bacterial cultures didn’t predict failure of antibiotic treatment in complex periprosthetic joints infection (PJI) patients undergoing 2-stage surgical revision or reimplantation.

Researchers included all consecutive patients that underwent 2-stage revisions in the management of PJI at a single centre between 2015 and 2018. The entire procedure involved the complete removal and debridement of the prosthesis and the implantation of a spacer made of gentamicin. Patients were debrided and reimplanted a new joint prosthesis after the spacer was removed.

During the second and first stages of the procedure, all patients were allowed to collect perioperative tissue, bone, joint fluid, and bone specimens. After the procedure, patients who had positive or negative bacteria cultures were given antibiotic treatment for 6 weeks and 10 days, respectively. Logistic regression was used for assessing predictors of positive bacteria cultures over a minimum of two years.

The analysis included 50 patients, of which the median age was 69 years (IQR, 62 to77 years), 64% of them were men and 48% had PJIs that involved the hip. Staphylococcus Aureus was the most common pathogen, with 36% of patients receiving it and coagulase -negative staphylococci 24%.

The second stage of the procedure yielded perioperative bacterial cultures that were positive for 20% and negative for 80% of patients. Patients with positive cultures were less likely than patients with negative cultures to receive a prosthesis for an inflammatory condition (50% vs. 10%), and less likely to receive an osteoarthritis implant (50% vs. 90%).

The rate of antibiotic treatment failure occurred at 0.07 (95% CI, 0.02-0.18), events per 1000 patient-days. Analysing Kaplan-Meier survival curves revealed no differences in the likelihood of antibiotic treatment failing based on perioperative tissue culture positivity. Similar results were also observed in terms of the duration of antibiotic therapy after the procedure. Multivariate analysis revealed that antibiotic failure was not associated with positive perioperative tissue cultures. Osteoarthritis (adjusted Odds ratio). [aOR]0.09; 95%CI, 0.01-0.65, P =.02); and inflammatory diseases (aOR 12.4; 95%CI, 1.46-1.53, P =.03); were both independently associated with positive bacteria cultures at reimplantation. Similar results were obtained for the duration of antibiotic treatment following the second stage.

This study was limited by its small sample size and heterogeneity in regard to the location of patients’ PJIs.

“Our findings suggest that with proper microbiological techniques (including automated grinding), cultures grow rapidly, and consequently, that post-reimplantation antibiotic [treatment] should not exceed 10 days,” the researchers concluded.

Reference Anastasia S, Jean-Michel U, David LP, et al. A two-year cohort of patients with periprosthetic joint infection: microbiology and antibiotics. Infect Dis Now. Published online June 24, 2022. doi:10.1016/j.idnow.2022.06.005

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