Abstract: Objective This study aimed to explore the pathogens and the antibiotic resistance in consecutive cases,and to provide a basis for the rational regarding antibiotic use.Methods We performed a retrospective chart review of all patients with pediatric hematology and oncology desease in Beijing Children's Hospital from January 2016 to June 2017. All patients were selected based on clinical presentation. Bacterial strains after removal of contaminated and colonized specimens were analyzed. The drug sensitivity test was determined by disk diffusion method or automatic instrument method according to the 2014 (CLSI) standard of American Clinical Laboratory Standardization Committee.Results Of all 2,188 strains isolated from 2,095 samples, 48.1% were gram-negative bacteria; 38.3% were gram-positive bacteria,and 13.6% were a fungal infection. The primary pathogens were gram-negative bacteria including Klebsiella pneumoniae,Pseudomonas aeruginosa, Enterobactercloacae, and Escherichia coli. Gram-positive bacteria were mainly coagulase-positive Staphylococcus epidermidis and human Staphylococcus. A total of methicillin-resistant Staphylococcus (MRS) gram-positive bacterial strains (41.6%,348/837) were identified, and Staphylococcus epidermidis (84.9%, 169/199) and human staphylococci (90.8%, 129/142) were the main types, but vancomycin- and linazolamide-resistant strains were not detected.Extended-spectrum β-lactamase-positive bacteria accounted for 31.9% (336/1 053)gram-negative bacteria, mainly K. pneumoniae(63.8%,134/210) and E. coli(92.8%, 90/97). As for gram-negative bacteria, there were 23.6% (248/1 053)carbapenem-resistant Enterobacteriaceae-positive bacteria, mainly K. pneumoniae(63.8%, 134/210),E. coli(51.5%, 50/97), and Enterobactercloacae(34.5%,38/110).The drug resistance rate for imipenem and meropenem was about or over 50%, but the resistance rate for tigecycline and amikacin was 0.9%-13.4% and 10%-26.8%, respectively. There were 86 Acinetobacter baumaniistrains, in which there were 32.6%(28/86) isolates drug-resistant A.baumanniistrains.The drug resistance rates of A. baumanii to carbapenem and polymyxin were 52.3%-58.1% and 1.2%.Conclusion Our report revealed a prevalence of pathogens of pediatric patients with hemato-oncological malignancies. The Gram-negative bacteria was the main pathogen. An increasing incidence of drug-resistant bacteria and opportunistic pathogens was demonstrated.

Key words: Drug-resistant bacteria, Hemato-oncological malignancies, Infection site, Pathogenic organic organismsin, Pediatric