Antimicrobial Susceptibility of Multi-drug Resistant Acinetobacter Baumannii and Pseudomonas Aeruginosa Isolates from 27 Hospitals in China

  Objective  To investigate the antimicrobial susceptibilities of nosocomial multi-drug resistantAcinetobacter baumannii(MDR-AB) and multi-drug resistant Pseudomonas aeruginosa(MDR-PA) isolates.

  Methods  MDR-AB and MDR-PA isolates were collected between August 2011 and July 2012 from 27 hospitals in China. All isolates were collected from high quality samples with definite infection diagnoses, whilst isolates from sputum and screen samples were strictly excluded. Minimum inhibitory concentrations (MICs) of 12 commonly used antimicrobial agents were tested by broth microdilution method in a microbiology laboratory. CLSI clinical breakpoints(CBPs) of pre- and post-revision were applied and compared in determination of MDR.

  Results  A total of 664 MDR-AB and 268 MDR-PA isolates were collected. Pan-drug resistant (PDR) was detected in four Pseudomonas aeruginosa but not in Acinetobacter baumannii. The majority of isolates were collected from ICUs and surgical wards. Colistin and tigecycline were the most active agents against MDR-AB (96.8% and 72.6% susceptible, respectively), while no other drug exhibited activity of > 55% susceptible. Only 72.4% of MDR-PA isolates remained susceptible to colistin, but amikacin was more active to MDR-PA (64.2%) than MDR-AB (16.7%). By applying revised CBPs, the susceptibility of MDR-AB isolates to imipenem and meropenem decreased by 1.3% and 0.6%, respectively, whereas the susceptibility of MDR-PA to these two drugs decreased by 5.5% and 8.6%, respectively. The carbapenems susceptible rate of isolates collected from ICUs was lower than surgical and other wards. Isolates collected from different geographic regions showed varied resistant profiles.

  Conclusions  Colistin and tigecycline are the most active drugs against MDR-AB, while colistin and amikacin have comparably good performance to MDR-PA.