title: In vitro and in vivo analysis of antimicrobial agents alone and in combination against multi-drug resistant Acinetobacter baumannii.
abstract: OBJECTIVE
  To investigate the in vitro and in vivo antibacterial activities of tigecycline and other 13 common antimicrobial agents, alone or in combination, against multi-drug resistant Acinetobacter baumannii.
  
  
  METHODS
  An in vitro susceptibility test of 101 A. baumannii was used to detect minimal inhibitory concentrations (MICs). A mouse lung infection model of multi-drug resistant A. baumannii, established by the ultrasonic atomization method, was used to define in vivo antimicrobial activities.
  
  
  RESULTS
  Multi-drug resistant A. baumannii showed high sensitivity to tigecycline (98% inhibition), polymyxin B (78.2% inhibition), and minocycline (74.2% inhibition). However, the use of these antimicrobial agents in combination with other antimicrobial agents produced synergistic or additive effects. In vivo data showed that white blood cell (WBC) counts in drug combination groups C (minocycline + amikacin) and D (minocycline + rifampicin) were significantly higher than in groups A (tigecycline) and B (polymyxin B) (P < 0.05), after administration of the drugs 24 h post-infection. Lung tissue inflammation gradually increased in the model group during the first 24 h after ultrasonic atomization infection; vasodilation, congestion with hemorrhage were observed 48 h post infection. After 3 days of anti-infective therapy in groups A, B, C, and D, lung tissue inflammation in each group gradually recovered with clear structures. The mortality rates in drug combination groups(groups C and D) were much lower than in groups A and B.
  
  
  CONCLUSIONS
  The combination of minocycline with either rifampicin or amikacin is more effective against multi-drug resistant A. baumannii than single-agent tigecycline or polymyxin B. In addition, the mouse lung infection by ultrasonic atomization is a suitable model for drug screening and analysis of infection mechanism.
authors.affiliation: The Affiliated First Hospital of Hangzhou, Zhejiang Chinese Medical University Hangzhou, China ; Department of Clinical Laboratories, Hangzhou First People's Hospital Hangzhou, China.
authors.forename: Songzhe
authors.initials: S
authors.lastname: He
authors.affiliation: The Affiliated First Hospital of Hangzhou, Zhejiang Chinese Medical University Hangzhou, China ; Department of Clinical Laboratories, Hangzhou First People's Hospital Hangzhou, China.
authors.forename: Hui
authors.initials: H
authors.lastname: He
authors.affiliation: The Affiliated First Hospital of Hangzhou, Zhejiang Chinese Medical University Hangzhou, China ; Department of Clinical Laboratories, Hangzhou First People's Hospital Hangzhou, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Clinical Laboratories, Hangzhou First People's Hospital Hangzhou, China.
authors.forename: Yueming
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Clinical Laboratories, Hangzhou First People's Hospital Hangzhou, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: The Affiliated First Hospital of Hangzhou, Zhejiang Chinese Medical University Hangzhou, China ; Department of Clinical Laboratories, Hangzhou First People's Hospital Hangzhou, China.
authors.forename: Daojun
authors.initials: D
authors.lastname: Yu
keywords: Acinetobacter baumannii; combination treatment; multi-drug resistant; pneumonia infection model; ultrasonic atomization