Conference Coverage

Extended Oral Antibiotics Linked to Altered PJI Microbiology

Ashton L. Stahl

Key Highlights

  • Among 1,088 patients with culture-positive periprosthetic joint infection (PJI), 25 had received extended oral antibiotics.
  • Gram-negative infections and polymicrobial PJI were more frequent among patients who received extended antibiotics.
  • Resistance to first-generation cephalosporins did not differ significantly between groups.

Extended oral antibiotics after primary total hip or knee arthroplasty (TKA) were associated with differences in the organisms causing subsequent periprosthetic joint infection, according to an abstract for the 2026 American Association of Hip and Knee Surgeons (AAHKS) Annual Meeting. Patients prescribed extended antibiotics had higher reported rates of gram-negative and polymicrobial infections, although resistance to first-generation cephalosporins did not differ significantly.

The researchers examined this association because extended oral antibiotic prescribing after primary arthroplasty has become increasingly common. According to the abstract, observational data suggest that this practice may reduce PJI risk in some high-risk patients. However, the authors identified infection with more difficult-to-treat organisms as a potential harm of additional antibiotic exposure.

Using a nationwide database, investigators identified patients who underwent primary total hip or knee arthroplasty, developed PJI within 1 year, and had positive culture data available. They specifically evaluated extended oral antibiotic exposure involving a first-generation oral cephalosporin.

The researchers reviewed antibiotic exposure, culture microbiology, and organism-specific antibiotic susceptibility profiles. They compared microbiology and antibiotic resistance rates between patients who received extended oral antibiotics and those who did not, using χ² and Fisher exact tests.

Study Findings

The analysis included 1,088 patients with PJI and available microbiology data; 25 had received extended oral antibiotics. In the extended-antibiotic group, 13 patients (52%) had infection involving a gram-negative organism, compared with 270 patients (reported as 23%) in the group without extended antibiotics (P = .002).

Polymicrobial PJI was also more frequent among patients who received extended antibiotics, occurring in 36% compared with 10% of those without extended antibiotic exposure (P < .001). The abstract characterized this as a threefold difference. Despite these microbiologic differences, resistance to first-generation cephalosporins did not differ significantly: 46% in the extended-antibiotic group versus 37% in the comparison group.

Clinical Implications

According to the study authors, the findings demonstrate that patients prescribed extended oral antibiotics had significantly different microbiology when subsequent PJI occurred. They emphasized that antibiotic exposure alters a patient’s microbiome and, consequently, the organisms causing infection.

Expert Commentary

“While our data does not indicate whether this shift led to worse outcomes, it is a useful reminder that antibiotic exposure alters a patient's microbiome, and therefore the organisms causing their infections,” the researchers concluded.

Reference

Blackburn BE, Gililland JM, Rainey JP, Certain LK. Extended oral antibiotics after primary hip or knee arthroplasty alter the microbiology of subsequent PJI. Paper #56. Abstract presented at the American Association of Hip and Knee Surgeons Annual Meeting, November 5–8, 2026, Dallas, TX.