Introduction: Intraoperative tissue culture remains the “gold standard” in diagnosing periprosthetic infection (PPI). However, an organism is not always cultured and this has been attributed to the fact that preoperative antibiotics were administered. This study intends to examine if preoperative antibiotics prevent isolation of intraoperative organisms.

Methods: 91 total joint arthroplasty patients diagnosed with PPI during (1999–2005) and who had positive aspiration culture were included in the study. All intravenous antibiotics that were given to the patient within seven days of surgery were documented. The total number of positive intraoperative fluid and tissue samples of patients who did and did not receive antibiotics was calculated. Susceptibility of the organism(s) to antibiotics was determined by antibiogram of the preoperative and intraoperative culture.

Results: 60 out of 91 patients received preoperative antibiotics within seven days of surgery. Antibiotics prevented isolation of an intraoperative organism in 6 out of the 60 (10%) cases. All of the 31 patients who did not receive any preoperative antibiotics had positive intraoperative cultures. Chi-square analysis revealed no significant difference between giving preoperative antibiotics within 7 days and isolating an intraoperative organism (p=0.068). Giving antibiotics that specifically targets the culprit organism did not significantly affect the fluid (p=0.585) or tissue culture yield (p=0.152) either.

Discussion: Although, giving preoperative antibiotics can prevent isolation of intraoperative organisms in 10% of cases, this is not statistically or clinically significant in patients with positive aspiration cultures because the organism is known beforehand. However, it is clinically and medicolegally relevant to withhold antibiotics in patients with negative aspiration cultures since the postoperative treatment antibiotic is tailored according to the organism cultured.