Biliary microbiome in pancreatic cancer: alterations with neoadjuvant therapy

Background: Neoadjuvant therapy for pancreatic cancer is being employed more commonly. Most of these patients undergo biliary stenting which results in bacterial colonization and more surgical site infections (SSIs). However, the influence of neoadjuvant therapy on the biliary microbiome has not been studied. Methods: From 2007 to 2017, patients at our institution who underwent pancreatoduodenectomy (PD) and had operative bile cultures were studied. Patient demographics, stent placement, bile cultures, bacterial sensitivities, SSIs and clinically-relevant postoperative pancreatic fistulas (CR-POPF) were analyzed. Patients who underwent neoadjuvant therapy were compared to those who went directly to surgery. Standard statistical analyses were performed. Results: Eighty-three patients received neoadjuvant therapy while 89 underwent surgery alone. Patients who received neoadjuvant therapy were more likely to have enterococci (45 vs 22%, p < 0.01), and Klebsiella (37 vs 19%, p < 0.01) in their bile. Resistance to cephalosporins was more common in those who received neoadjuvant therapy (76 vs 60%, p < 0.05). Neoadjuvant therapy did not affect the incidence of SSIs or CR-POPFs. Conclusion: The biliary microbiome is altered in patients undergoing pancreatoduodenectomy (PD) after neoadjuvant therapy. Most patients undergoing PD with a biliary stent have microorganisms resistant to cephalosporins. Antibiotic prophylaxis in these patients should cover enterococci and gram-negative bacteria.