Surveillance of Antimicrobial Resistance among Clinical Isolates from Surgery Wards in Peking Union Medical College Hospital

  Objective  To investigate the distribution and antimicrobial resistance of clinical isolates from surgery wards in Peking Union Medical College Hospital (PUMCH).

  Methods  A total of 3084 non-duplicate clinical isolates were collected from PUMCH surgery wards during the period from January 1, 2012 to December 31, 2013. Disc diffusion test (Kirby-Bauer method) and automated systems were employed to detect the antimicrobial resistance of these isolates. The data were analyzed by WHONET 5.6 software according to Clinical and Laboratory Standards Institute 2013 breakpoints.

  Results  Of the 3084 clinical isolates, the 10 most common bacteria isolated were:A.baumannii(14.1%), E.coli (12.4%), P.aeruginosa(12.4%), K.pneumonia(11.8%), S.aureus(8.9%), E.faecalis(5.4%), coagulase-negative staphylococcus(5.3%), E.cloacae(3.7%), S.maltophilia(3.6%) and E.faecium(3.2%), in which gram-negative bacteria accounted for 71.6% (2208 isolates) and gram-positive accounted for 28.4% (876 isolates). In S.aureus and coagulase-negative staphylococcus, methicillin-resistant strains (MRSA and MRCNS) accounted for 42.7% (117/274) and 77.3% (119/154), respectively. The resistance rates of methicillin-resistance strains to β-lactams and other antimicrobial agents were much higher than those of methicillin-susceptive strains including methicillin-susceptible Staphylococcus aureus(MSSA) and methicillin-susceptible coagulase-negative Staphylococcus(MSCNS). In addition, 80.3% of MRSA strains were still susceptible to trimethoprim-sulfamethoxazole, while 95.0% of MRCNS strains were susceptible to rifampin. No staphylococcal strains were found resistant to vancomycin, teicoplanin, or linezolid. The drug resistance rates of E.faecalis strains to most antimicrobials tested were much lower than those of E.faecium, except for the resistance rate to chloramphenicol, which was only 4.3% in E.faecium. One strain of E.faecalis and 5 strains of E.faecium were found resistant to vancomycin. No linezolid-resistant strains were found in enterococcal isolates. Extended spectrum β-lactamases (ESBLs)-producing strains accounted for 56.7% (217/383), 23.8% (97/408), and 22.8% (13/57) in E.coli, Klebsiella species(K.pneumoniae and K.oxytoca), and P.mirabilis, respectively. The drug resistance rates of ESBLs-producing strains were higher than the corresponding non-ESBLs-producing strains. Enterobacteriaceae strains were still highly susceptible to carbapenems, the overall resistance rates being 1.6%-3.3%. A few pan-resistant strains of K. pneumoniae(0.8%, 3/363)were identified. The resistance rates of P.aeruginosa to imipenem and meropenem were 19.5% and 15.0%, respectively, while the resistance rate to amikacin was the lowest (8.6%). The resistance rates of A.baumannii to imipenem and meropenem were 74.1% and 74.0%, respectively, compared with the lowest resistance rates to cefoperazone-sulbactam (51.5%) and minocycline (28.9%). The prevalence of pan-resistant strains in A.baumannii and P.aeruginosa were 44.3% (193/436) and 0.8% (3/381), respectively.

  Conclusion  Regular surveillance of bacterial resistance could provide practical guidance of rational selection of antimicrobial agents for clinicians.