title: High prevalence of Legionella in non-passenger merchant vessels.
abstract: There is a paucity of information on the risk from potable water in non-passenger merchant vessels (NPMVs) particularly with regard to Legionella and other bacteria. This retrospective study examined water samples from 550 NPMVs docked in eight UK ports. A total of 1027 samples from 412 NPMVs were examined for total aerobic colony counts (ACC), coliforms, Escherichia coli and enterococci; 41% of samples yielded ACC above the action level (>1 × 103 c.f.u./ml) and 4·5% contained actionable levels (>1 c.f.u./100 ml) of faecal indicator bacteria. Eight hundred and three samples from 360 NPMVs were cultured specifically for Legionella and 58% of vessels proved positive for these organisms with 27% of samples showing levels greater than the UK upper action limit of 1 × 103 c.f.u./l. Cabin showers (49%) and hospital shower (45%) were frequently positive. A subset of 106 samples was analysed by quantitative polymerase chain reaction for Legionella and identified a further 11 Legionella-positive NPMVs, returning a negative predictive value of 100%. There was no correlation between NPMV age or size and any microbial parameters (P > 0·05). Legionella pneumophila serogroup 1 was isolated from 46% of NPMVs and sequence-based typing of 17 isolates revealed four sequence types (STs) previously associated with human disease. These data raise significant concerns regarding the management of microbial and Legionella risks on board NPMVs and suggest that better guidance and compliance are required to improve control.
authors.affiliation: Biosafety, Air and Water Microbiology Group,National Infection Service,Public Health England,Porton,UK.
authors.forename: S L
authors.identifier: 0000-0003-4721-0040
authors.initials: SL
authors.lastname: Collins
authors.affiliation: Biosafety, Air and Water Microbiology Group,National Infection Service,Public Health England,Porton,UK.
authors.forename: D
authors.initials: D
authors.lastname: Stevenson
authors.affiliation: Respiratory and Vaccine Preventable Bacteria Reference Unit,Public Health England,Colindale,London,UK.
authors.forename: M
authors.initials: M
authors.lastname: Mentasti
authors.affiliation: Northern Ireland Public Health Laboratory,Belfast Health and Social Care Trust,Belfast City Hospital,Belfast,UK.
authors.forename: A
authors.initials: A
authors.lastname: Shaw
authors.affiliation: Food, Water and Environmental Microbiology Laboratory,National Infection Service,Public Health England,Colindale,London,UK.
authors.forename: A
authors.initials: A
authors.lastname: Johnson
authors.affiliation: Manchester Port Health Authority,Runcorn,Cheshire,UK.
authors.forename: L
authors.initials: L
authors.lastname: Crossley
authors.affiliation: Food, Water and Environmental Microbiology Laboratory,National Infection Service,Public Health England,Porton,UK.
authors.forename: C
authors.initials: C
authors.lastname: Willis
mesh_terms: D058491:Bacterial Load; D060766:Drinking Water / Q000382:microbiology*; D016983:Enterococcus / Q000302:isolation & purification; D004926:Escherichia coli / Q000302:isolation & purification; D005838:Genotype; D007875:Legionella / Q000302:isolation & purification*; D058889:Molecular Typing; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D012767:Ships; D006113:United Kingdom
chemical_list: D060766:Drinking Water
keywords: 
                 Legionella
              ; water (quality); water (safe); water-borne infections