title: Nanosilver-marine fungal chitosan as antibiotic synergizers against sepsis fish bacteria.
abstract: OBJECTIVE
  Mortality is highly variable within population of cultured fish due to virulent bacteria causing fish septicemia. The use of nano-silver marine fungal chitosan as antibiotic synergisers could be an alternative in the treatment of sepsis fish pathogens.
  
  
  METHODS
  Different bulk chitosan solutions were prepared from the mycelia of four marine fungi (Aspergillus terreus, Aspergillus flavipes, Tricoderma hamatum and Fennellia flavipes) and used as capping agents for silver nanoparticles. In vitro, the antibacterial activity of these preparations was determined against nine fish-sepsis causing bacteria, alone and in combination with nine antibiotics of choice used in aquaculture. Prepared fungal chitosans (CsF) were characterized by yield of chistosan obtained, degree of deacetylation and viscosity.
  
  
  CONCLUSIONS
  The maximum yield of chitosan (28%) was obtained from Aspergillus terreus. A. terreus chitosan (CsF), silver nanoparticles (AgNPs) and chitosan-silver nanoparticles (CsF-AgNPs) showed maximum activity at the minimum inhibitory concentrations average (MICAVG) 27.2, 18.2 and 7.9 μg/ml, respectively. Combination of CsF -AgNPs with amikacin (Ak) and rifampicin (RD) reduced the MIC values by 96 and 94%, respectively, with fractional inhibitory concentration index (FICI) = 0.42 and 0.50 as synergistic effect. It is promising to use CsF-AgNPs as enhancing agent in combination with antibiotics for fish sepsis therapy.
authors.affiliation: Microbiology Lababoratoy, Marine Environment Division, National Institute of Oceanography & Fisheries.
authors.forename: Khouloud Mohamed
authors.initials: KM
authors.lastname: Barakat
authors.affiliation: Botany and Microbiology Depart, Faculty of Science, Alexandria University.
authors.forename: Yousri Mahmoud
authors.initials: YM
authors.lastname: Gohar
keywords: Marine fungal chitosan; antibiotics; bacterial sepsis; nanosilver; synergy