title: High diversity of bacterial pathogens and antibiotic resistance in salmonid fish farm pond water as determined by molecular identification employing 16S rDNA PCR, gene sequencing and total antibiotic susceptibility techniques.
abstract: The aim of this study was to examine the microbiological and related parameters (antibiotic resistance and pathogen identification) of water at two salmonid fish farms in Northern Ireland. Total Bacterial Counts at the Movanagher Fish Farm was 1730 colony forming units (cfu)/ml water (log10 3.24cfu/ml) and 3260cfu/ml (log10 3.51cfu/ml) at the Bushmills Salmon Station. Examination of resulting organisms revealed 10 morphological phenotypes, which were subsequently sequenced to determine their identification. All these organisms were Gram-negative and no Gram-positive organisms were isolated from any water sample. From these phenotypes, eight different genera were identified including Acinetobacter, Aeromonas, Chryseobacterium, Erwinia, Flavobacterium, Pseudomonas and Rheinheimera. One unnamed novel taxon was identified from water at the Movanagher Fish Farm, belonging to the genus Acinetobacter and has been tentatively named Acinetobacter movanagherensis. No other novel taxa were observed. All but one of these environmental organisms (Erwinia) are potential pathogens of fish disease. Total antibiotic resistance was observed to varying degrees in water specimens. The most resistant populations were observed in water taken from the Bushmills Salmon Station inlet, followed by water from the Movanagher Fish Farm. No resistance was observed against tetracycline and there was only one occurrence of resistance against ciprofloxacin. Overall, this study indicates that potential fish pathogens made up the majority of environmental organisms identified, even in the absence of recorded fish disease. There was also relatively high levels of total antibiotic resistance in the bacterial water populations examined, where tetracycline was the only antibiotic with zero resistance. These data indicate that the threat of bacterial disease is relatively close due to the indigenous colonization of farm water and that husbandry standards should be maintained at a high standard to avert bacterial disease outbreaks, rather than relying on the absence of specific pathogens in the immediate farm environment.
authors.affiliation: Northern Ireland Public Health Laboratory, Department of Bacteriology, Belfast City Hospital, Lisburn Road, Belfast, Northern Ireland, BT9 7AD, UK; School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK; Centre for Infection & Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen's University, Health Sciences, Building, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7BL, UK. Electronic address: jemoore@niphl.dnet.co.uk.
authors.forename: John E
authors.initials: JE
authors.lastname: Moore
authors.affiliation: Department of Medical Technology, Xi'an Medical College, Xi'an, Shaanxi 710021, China.
authors.forename: Junhua
authors.initials: J
authors.lastname: Huang
authors.affiliation: Shaanxi Center for Disease Control and Prevention, 3 Jian Dong Street, Xi'an, Shaanxi 710054, China.
authors.forename: Pengbo
authors.initials: P
authors.lastname: Yu
authors.affiliation: Xi'an Center for Disease Control and Prevention, Xi'an, Shaanxi 710054, China.
authors.forename: Chaofeng
authors.initials: C
authors.lastname: Ma
authors.affiliation: Northern Ireland Public Health Laboratory, Department of Bacteriology, Belfast City Hospital, Lisburn Road, Belfast, Northern Ireland, BT9 7AD, UK; Ballymena Academy, Galgorm Road, Ballymena, Co. Antrim, Northern Ireland, BT42 1AJ, UK.
authors.forename: Peter Ja
authors.initials: PJ
authors.lastname: Moore
authors.affiliation: Northern Ireland Public Health Laboratory, Department of Bacteriology, Belfast City Hospital, Lisburn Road, Belfast, Northern Ireland, BT9 7AD, UK.
authors.forename: Beverley C
authors.initials: BC
authors.lastname: Millar
authors.affiliation: Northern Ireland Public Health Laboratory, Department of Bacteriology, Belfast City Hospital, Lisburn Road, Belfast, Northern Ireland, BT9 7AD, UK.
authors.forename: Colin E
authors.initials: CE
authors.lastname: Goldsmith
authors.affiliation: Department of Pathogenic Biology, Xian Jiatong University, Xi'an, Shaanxi, China.
authors.forename: Jiru
authors.initials: J
authors.lastname: Xu
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents; D017756:Aquaculture; D004269:DNA, Bacterial / Q000737:chemistry*; D004275:DNA, Ribosomal / Q000737:chemistry; D024881:Drug Resistance, Bacterial; D008826:Microbial Sensitivity Tests; D017686:Oncorhynchus mykiss; D016133:Polymerase Chain Reaction; D061005:Ponds / Q000382:microbiology*; D011549:Pseudomonas / Q000302:isolation & purification; D020317:Salmo salar; D014871:Water Microbiology
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004275:DNA, Ribosomal
keywords: Antibiotic resistance; Aquaculture; Bacterial pathogen; Environment; Fish farming; Salmon