Abstract: Objective To investigate the distribution of pathogens and changes in serum human β-defendin-3(HBD3) and FMS like tyrosine kinase 3 ligand(Flt3L) levels in patients with pulmonary infection after esophageal cancer radical surgery.Methods Prospectively, patients who underwent radical resection of esophageal cancer and developed pulmonary infection from January 2022 to January 2024 were selected as the infection group (75 cases), and patients who underwent radical resection of esophageal cancer and did not develop pulmonary infection were selected as the non-infection group (93 cases).Patients in the infection group were divided into the mild group (25 cases), the moderate group (39 cases), and the severe group (11 cases) based on the CURB-65 score. The distribution of pathogenic bacteria in patients of the infection group was analyzed by the fully automatic microbial identification instrument. The expression levels of HBD3 and Flt3L in serum were detected by enzyme-linked immunosorbent assay (ELISA).Multivariate Logistic regression was applied to analyze the risk factors for postoperative pulmonary infection in esophageal cancer patients.ROC curve was applied to analyze the diagnostic value of HBD3 and Flt3L levels for postoperative pulmonary infection in esophageal cancer patients.Results Among 75 infected patients,90 strains of pathogens were detected,including 49 strains(54.44%) of Gram negative bacteria,29 strains(32.22%) of Gram positive bacteria,and 12 strains(13.33%) of fungi.The serum HBD3 and Flt3L levels in the infection group were greatly higher than those in the non infection group(P＜0.05).The serum HBD3 and Flt3L levels in the severe group were higher than those in the moderate group and mild group(P＜0.05),while the serum HBD3 and Flt3L levels in the moderate group were higher than those in the mild group(P＜0.05).Multivariate Logistic regression analysis showed that HBD3,Flt3L,tumor location in the upper/middle segment,intraoperative bleeding ≥ 500 ml,diabetes,and smoking history were all factors influencing the pulmonary infection after radical resection of esophageal cancer(P＜0.05).According to the ROC curve,the AUC value for diagnosing postoperative pulmonary infection in esophageal cancer patients with serum HBD3 level alone was 0.789.The AUC value for diagnosing postoperative pulmonary infection in esophageal cancer patients with serum Flt3L level alone was 0.863,the AUC value of the combined diagnosis of the two was 0.934,which was greatly higher than that of the individual diagnosis(Z_{combination vs HBD3}=3.723,Z_{combination vs Flt3L}=2.098,P＜0.05).Conclusion The serum HBD3 and Flt3L levels in patients with pulmonary infection after esophageal cancer radical surgery are highly expressed,and the serum HBD3 and Flt3L levels are correlated with the severity of pulmonary infection.The two are risk factors for postoperative pulmonary infection in esophageal cancer patients after radical surgery,and their combination can effectively diagnose postoperative pulmonary infection in esophageal cancer patients.

Key words: radical surgery for esophageal cancer;pulmonary infection;pathogenic bacteria;human β-defendin-3;FMS like tyrosine kinase 3 ligand