Objective:Infection is the most common complication in patients with malignant tumors and an important cause of death. According to statistics, 60% to 70% of the leukemia / lymphoma died of infection. Children with malignant tumors are often prone to bacterial infections, bacteremia and other complications during the chemotherapy period, so it could be worse and even dead.Therefore the pediatric physicians must face the difficulty to find out the pathogens which caused infection.The intestine is the body's ...