title: Plant essential oils against Aeromonas hydrophila: in vitro activity and their use in experimentally infected fish.
abstract: OBJECTIVE
  The aims of this study were to investigate the in vitro antibacterial activity of the essential oils (EOs) of Hesperozygis ringens (HREO), popularly known as 'espanta-pulga' and two different species of basil, Ocimum gratissimum (OGEO) and Ocimum americanum (OAEO), as well as, the potential of these products to be used in silver catfish (Rhamdia quelen) infected with Aeromonas hydrophila.
  
  
  RESULTS
  OGEO and HREO showed better antibacterial activity in vitro. Subinhibitory concentrations of all EOs inhibited haemolysis caused by Aer. hydrophila in fish erythrocytes (100% reduction for OAEO at 100 μg ml(-1) and more than 90% for HREO and OGEO at 150 μg ml(-1) ). However, OAEO and HREO showed the best survival results (75 and 70% respectively) after their use as treatment (therapeutic baths-1 h daily/5 days) in silver catfish experimentally infected with Aer. hydrophila. A second in vivo assay using healthy fish was conducted to verify the potential of the EOs (preventive baths-1 h daily/5 days) to promote fish survival. Fish exposed to HREO and OAEO and their diluent (ethanol) showed significant lower haematocrit values and higher complement system activity compared to control. Plasma cortisol level was significantly higher in the groups exposed to both EOs. There was no significant difference in survival of silver catfish challenged with Aer. hydrophila after preventive baths with HREO, OAEO and control group.
  
  
  CONCLUSIONS
  All tested EOs showed in vitro antibacterial properties against Aer. hydrophila and HREO and OAEO showed potential to be used in the treatment of infected fish.
  
  
  CONCLUSIONS
  These products can be used in aquaculture as therapeutic and prophylactic agents against fish pathogens, with antimicrobial and/or immunostimulant properties.
authors: Departamento de Fisiologia e Farmacologia, Universidade Federal de Santa Maria, Santa Maria, Brazil.
authors: F J
authors: FJ
authors: Sutili
authors: Curso de Farmácia, Universidade Regional Integrada do Alto Uruguai e Missões, Santiago, Brazil.
authors: L de Lima
authors: Lde L
authors: Silva
authors: Departamento de Fisiologia e Farmacologia, Universidade Federal de Santa Maria, Santa Maria, Brazil.
authors: L T
authors: LT
authors: Gressler
authors: Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria, Santa Maria, Brazil.
authors: L T
authors: LT
authors: Gressler
authors: Departamento de Zootecnia e Ciências Biológicas/CESNORS, Universidade Federal de Santa Maria, Palmeira das Missões, Brazil.
authors: E K
authors: EK
authors: Battisti
authors: Departamento de Farmácia Industrial, Universidade Federal de Santa Maria, Santa Maria, Brazil.
authors: B M
authors: BM
authors: Heinzmann
authors: Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria, Santa Maria, Brazil.
authors: A C
authors: AC
authors: de Vargas
authors: Departamento de Fisiologia e Farmacologia, Universidade Federal de Santa Maria, Santa Maria, Brazil.
authors: B
authors: B
authors: Baldisserotto
mesh_terms: D016980:Aeromonas hydrophila / Q000187:drug effects* / Q000254:growth & development; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D002397:Catfishes / Q000382:microbiology; D005393:Fish Diseases / Q000188:drug therapy / Q000382:microbiology*; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D019686:Lamiaceae / Q000737:chemistry; D031339:Ocimum / Q000737:chemistry; D018649:Ocimum basilicum / Q000737:chemistry; D009822:Oils, Volatile / Q000494:pharmacology*; D010936:Plant Extracts / Q000008:administration & dosage*
chemical_list: D000900:Anti-Bacterial Agents; D009822:Oils, Volatile; D010936:Plant Extracts
keywords: Hesperozygis ringens; Ocimum americanum; Ocimum gratissimum; Rhamdia quelen; cortisol; innate immune system