The Influence of Antibiotic Prophylaxis on Intraoperative Prosthetic Joint Infection Cultures

Total joint replacement is a common clinical practice for patients suffering from disabling arthritis, since it provides significant pain relief and functional recovering. Nevertheless, its outcome is compromised by complications such as periprosthetic joint infection (PJI), which is reported to occur in 1 to 4% of primary total knee arthroplasties (TKA), and approximately 1% of primary total hip replacements (THR). Despite all efforts to restrain PJI, its prevalence may reach even higher proportions if patients undergo a resection arthroplasty or irrigation and débridement for infected prosthesis. That said, timely diagnosis and early isolation of the infected microorganism is utterly important, if proper care is to be delivered.

The gold standard for the diagnosis of PJI is the isolation of a microorganism from the intraoperative cultures, combined with the sonication from retrieved joint implants1. This technique applies sound energy to agitate and disrupt biofilm, dislodging adherent bacterias to the bone cement, which has been proved to be a more sensitive method than conventional intraoperative cultures. False-negative percentages were reported to be 15% in patients who did not receive extended antibiotic prophylaxis and 60% if extended antibiotic therapy was administered.

Regardless of an adequate clinical, radiographic and surgical suspicion confirming PJI, an organism is not always successfully isolated from the intraoperative cultures, which increases false negatives results. This fact has been trying to be explained by several authors, some of which postulate that antibiotic prophylaxis could interfere with the isolation of the microorganism from the intraoperative cultures. As a result, and acting accordingly to this hypothesis, preoperative antibiotics are often withheld until intraoperative cultures are obtained, hoping that tissues are not loaded with antibiotics. Nevertheless, one should be aware of the adverse consequences of this practice that may result in systemic dissemination of infection.

Moreover, Ghanem and Stephen recently concluded that antibiotic prophylaxis does not interfere with the isolation of the microorganism from intraoperative cultures, despite being studies that lack statistical power.

Therefore, it is clear that reported studies in this field support both preoperative antibiotic prophylaxis administration, as well its withdrawal, until intraoperative cultures are obtained.

This decision in the department study depends exclusively on the treating surgeon judgment. In fact, 48% of all patients admitted at the study hospital with PJI receive preoperative antibiotic prophylaxis, which could be related to higher false-negative intraoperative culture and sonication results. Thus, the investigators add substances with chelation properties to hemoculture containers and then inoculate sonication samples. This practice offsets antibiotic interference with intraoperative cultures and has proved to enhance microorganism detection rates.

That said, and given the lack of scientific evidence about this clinical practice the investigators are willing to engage a prospective randomized double-blind clinical trial, that will allow us to determine whether intraoperative cultures and sonication samples are affected by antibiotic prophylaxis.