Objective  To observe the distribution of pathogens of combined infection in patients after rectal cancer operation during radiotherapy, and to analyze the influencing factors of infection.

  Methods  The clinical data of 500 patients with rectal cancer was retrospectively analyzed, all patients received adjuvant chemoradiotherapy before operation, then received radical resection, and received chemoradiotherapy 1 month after operation. The incidence of infection and the distribution of pathogenic bacteria during radiotherapy and chemotherapy were analyzed, and the influencing factors of nosocomial infection were analyzed.

  Results  In 500 patients with rectal cancer, 49 cases had nosocomial infection during chemoradiotherapy after operation, the infection rate was 9.80%. A total of 62 strains of pathogens were isolated from 49 patients with nosocomial infection, the proportions of Gram-negative bacteria including Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii and so on were the highest, no fungus was detected. Logistic regression analysis showed that tumors in stage Ⅲ, combining with diabetes mellitus, low white blood cell count and various prophylactic antibiotics used were the influencing factors of nosocomial infection in patients with radiotherapy after rectal cancer operation (OR>1, P < 0.05).

  Conclusion  Gram-negative bacteria are the main pathogens of nosocomial infection during radiotherapy after rectal cancer operation, high tumor stage, combining with diabetes mellitus, low white blood cell count and various prophylactic antibiotics used may be the influencing factors of infection during radiotherapy. Therefore, the situations should be emphasized in clinic.