title: Synergistic effects of ethnomedicinal plants of Apocynaceae family and antibiotics against clinical isolates of Acinetobacter baumannii.
abstract: OBJECTIVE
  To investigate the efficacy of 17 ethnomedicinal plants belonging to Apocynaceae family used in combination with 16 conventional antibiotics against non-multidrug resistant-, multidrug resistant (MDR)-, and extensive drug resistant (XDR) Acinetobacter baumannii (A. baumannii).
  
  
  METHODS
  Antibacterial activity and resistance modifying ability of 272 combinations were determined by growth inhibition assays and further confirmed by time-kill assay.
  
  
  RESULTS
  Among the combinations of the antibiotics with Apocynaceae ethanol extracts on this pathogen, 15 (5%) had synergistic effects, 23 (8%) had partial synergistic effects and 234 (86%) had no effects. Synergistic activity was observed mostly when the Apocynaceae extracts were combined with rifampicin or cefazolin. Interestingly, 10 out of 17 combinations between the extracts and rifampicin displayed synergistic or partial synergistic behaviors. Holarrhena antidysenterica extract was additionally tested to restore rifampicin activity against clinical isolates of MDR and XDR A. baumannii. With respect to total or partial synergy, 70% was XDR A. baumannii isolates and 66% was MDR A. baumannii isolates.
  
  
  CONCLUSIONS
  Holarrhena antidysenterica extract clearly demonstrated the ability to restore rifampicin activity against both A. baumannii ATCC19606 and clinically isolated A. baumannii. Additional studies examining its active principles as well as mechanisms of actions such as the effects on efflux pumps and outer membrane permeability alterations are recommended.
authors: Faculty of Traditional Thai Medicine, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Natural Product Research Center of Excellence, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address: sasitorn.chu@psu.ac.th.
authors: Sasitorn
authors: S
authors: Chusri
authors: Faculty of Traditional Thai Medicine, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
authors: Thanyaluck
authors: T
authors: Siriyong
authors: Department of Microbiology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
authors: Pinanong
authors: P
authors: Na-Phatthalung
authors: Natural Product Research Center of Excellence, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Department of Microbiology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
authors: Supayang Piyawan
authors: SP
authors: Voravuthikunchai
mesh_terms: D000151:Acinetobacter Infections / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D029062:Apocynaceae / Q000737:chemistry*; D024901:Drug Resistance, Multiple, Bacterial; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts
keywords: Acinetobacter baumannii; Antibacterial activity; Apocynaceae; Combination; Resistance modifying agents; Synergistic effect