title: A micro-dilution method for detecting oxytetracycline-resistant bacteria in marine sediments from salmon and mussel aquaculture sites and an urbanized harbour in Atlantic Canada.
abstract: A micro-dilution technique with changes in optical density (OD) used to measure bacterial growth over 72 h in culture media containing 0, 5, 10, 20, 40, 80 and 160 microg OTC (oxytetracycline)ml(-1) was applied to determine growth inhibition (GI) in mixed bacterial strains cultured from samples of marine sediments and salmon feed pellets. Growth of control cultures (Aeromonas salmonicida) was inhibited at all OTC concentrations. Some feed pellet samples and under-cage sediments from salmon aquaculture sites in the Bay of Fundy showed GI up to > or = 160 microg OTCml(-1). Lower values (40 to 80 microg OTC ml(-1)) occurred in subsurface (5-18 cm) sediments, > 100 m from salmon pens and adjacent to sewage outfalls in Halifax Harbour. GI values < 20 microg OTC ml(-1) in sediment from reference locations in Halifax Harbour and mussel aquaculture sites are considered to reflect natural background levels for OTC resistance.
authors.affiliation: Ecosystem Research Division, Department of Fisheries and Oceans, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada B2Y 4A2. hargraveb@rogers.com
authors.forename: Barry T
authors.initials: BT
authors.lastname: Hargrave
authors.forename: Lisa I
authors.initials: LI
authors.lastname: Doucette
authors.forename: Kats
authors.initials: K
authors.lastname: Haya
authors.forename: Faron S
authors.initials: FS
authors.lastname: Friars
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Armstrong
mesh_terms: D048409:Aeromonas salmonicida / Q000187:drug effects* / Q000254:growth & development; D000818:Animals; D017756:Aquaculture; D001267:Atlantic Ocean; D049872:Bivalvia / Q000254:growth & development; D002170:Canada; D024881:Drug Resistance, Bacterial; D019015:Geologic Sediments / Q000382:microbiology*; D007201:Indicator Dilution Techniques; D010118:Oxytetracycline / Q000633:toxicity*; D012474:Salmon / Q000254:growth & development; D014505:Urban Population; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D010118:Oxytetracycline