title: Antibacterial therapeutics for the treatment of chytrid infection in amphibians: Columbus's egg?
abstract: BACKGROUND
  The establishment of safe and effective protocols to treat chytridiomycosis in amphibians is urgently required. In this study, the usefulness of antibacterial agents to clear chytridiomycosis from infected amphibians was evaluated.
  
  
  RESULTS
  Florfenicol, sulfamethoxazole, sulfadiazine and the combination of trimethoprim and sulfonamides were active in vitro against cultures of five Batrachochytrium dendrobatidis strains containing sporangia and zoospores, with minimum inhibitory concentrations (MIC) of 0.5-1.0 μg/ml for florfenicol and 8.0 μg/ml for the sulfonamides. Trimethoprim was not capable of inhibiting growth but, combined with sulfonamides, reduced the time to visible growth inhibition by the sulfonamides. Growth inhibition of B. dendrobatidis was not observed after exposure to clindamycin, doxycycline, enrofloxacin, paromomycin, polymyxin E and tylosin. Cultures of sporangia and zoospores of B. dendrobatidis strains JEL423 and IA042 were killed completely after 14 days of exposure to 100 μg/ml florfenicol or 16 μg/ml trimethoprim combined with 80 μg/ml sulfadiazine. These concentrations were, however, not capable of efficiently killing zoospores within 4 days after exposure as assessed using flow cytometry. Florfenicol concentrations remained stable in a bathing solution during a ten day period. Exposure of Discoglossus scovazzi tadpoles for ten days to 100 μg/ml but not to 10 μg florfenicol /ml water resulted in toxicity. In an in vivo trial, post metamorphic Alytes muletensis, experimentally inoculated with B. dendrobatidis, were treated topically with a solution containing 10 μg/ml of florfenicol during 14 days. Although a significant reduction of the B. dendrobatidis load was obtained, none of the treated animals cleared the infection.
  
  
  CONCLUSIONS
  We thus conclude that, despite marked anti B. dendrobatidis activity in vitro, the florfenicol treatment used is not capable of eliminating B. dendrobatidis infections from amphibians.
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Merelbeke, Belgium.
authors.forename: Mariska
authors.initials: M
authors.lastname: Muijsers
authors.forename: An
authors.initials: A
authors.lastname: Martel
authors.forename: Pascale
authors.initials: P
authors.lastname: Van Rooij
authors.forename: Kris
authors.initials: K
authors.lastname: Baert
authors.forename: Griet
authors.initials: G
authors.lastname: Vercauteren
authors.forename: Richard
authors.initials: R
authors.lastname: Ducatelle
authors.forename: Patrick
authors.initials: P
authors.lastname: De Backer
authors.forename: Francis
authors.initials: F
authors.lastname: Vercammen
authors.forename: Freddy
authors.initials: F
authors.lastname: Haesebrouck
authors.forename: Frank
authors.initials: F
authors.lastname: Pasmans
mesh_terms: D000663:Amphibians; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D000935:Antifungal Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D001835:Body Weight / Q000187:drug effects; D008411:Chytridiomycota / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D008826:Microbial Sensitivity Tests
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents