Objective  To investigate the antimicrobial resistance of clinical bacterial isolates in Peking Union Medical College Hospital (PUMCH) in 2016.

  Methods  A total of 11 721 non-duplicate clinical isolates were collected from January 1 to December 31 2016. Disc diffusion test (Kirby-Bauer method) and automated systems were employed to detect antimicrobial resistance. The data were analyzed by WHONET 5.6 software according to the 2016 edition of Performance Standards for Antimicrobial Susceptibility Testing issued by The Clinical and Laboratory Standards Institute (CLSI) of the United States.

  Results  Of the 11 721 clinical isolates, the 10 most common bacteria were:Escherichia coli (16.3%), Klebsiella pneumoniae (11.4%), Pseudomonas aeruginosa (9.3%), Acinetobacter baumannii (9.0%), Staphylococcus aureus (7.4%), coagulase-negative Staphylococcus (7.3%), Enterococcus faecalis (6.1%), Enterococcus faecium (3.9%), Streptococcus agalactiae (3.4%) and Enterobacter cloacae (3.3%). Gram-negative bacilli and gram-positive cocci accounted for 62.7% and 37.3%, respectively. Methicillin-resistant strains in S. aureus (MRSA) and coagulase-negative Staphylococcus (MRCNS) accounted for 27.0% and 68.9%, respectively. The resistance rates of MRSA and MRCNS strains to β-lactams and other antimicrobial agents were much higher than those of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-susceptive coagulase-negative Staphylococcus (MSCNS) strains. 93.9% of MRSA strains were still susceptible to trimethoprim-sulfamethoxazole, while 85.0% of MRCNS strains were susceptible to rifampin. No staphylococcal strains resistant to vancomycin, teicoplanin, and linezolid were detected. The resistance rate of E. faecalis strains to most of the antimicrobial agents tested (except Chloramphenicol) was much lower than that of E. faecium, while some strains resistant to vancomycin were found in both species. 97.4% of β-hemolytic streptococcus strains were susceptible to penicillin. Extended-spectrum β-lactamase (ESBL)-producing strains accounted for 50.7%(969/1913), 33.9%(488/1439) and 32.1%(59/184) in E. coli, Klebsiella spp (K. pneumoniae and K. oxytoca) and P. mirabilis, respectively. Enterbacteriaceae strains were still highly susceptible to carbapenems, with an overall resistance rate of ≤ 7.3%. A few extensively resistant strains of K. pneumoniae (6.5%, 87/1331) were identified. The resistance rates of K. pneumoniae to imipenem and meropenem were 18.0% and 16.6%, respectively. About 76.7% of A. baumannii were resistant to imipenem, and 74.4% to meropenem, while the resistant rates to tigecycline (9.3%) and minocycline (26.9%) were the lowest. The resistance rates of P. aeruginosa to imipenem and meropenem were 26.3% and 18.5%, respectively, while the resistant rate (8.2%) to amikacin was the lowest. The prevalence of extensively resistant strains in A. baumannii and P. aeruginosa was 24.8% (260/1049) and 3.1% (34/1095), respectively.

  Conclusions  The prevalence of carbapenem-resistant K. pneumonia is still higher. Infections due to carbapenem-resistant strains pose a huge challenge for clinicians.