title: Aerococcus viridans var. homari: The presence of capsule and the relationship to virulence in American lobster (Homarus americanus).
abstract: The relationship between virulence and encapsulation of Aerococcus viridans var. homari was evaluated by growing virulent (Rabin's) and avirulent (ATCC 10400) strains under varying culture conditions, and during challenge trials. Changes in capsule thickness were monitored using a modified lysine-ruthenium red (LRR) fixation method and transmission electron microscopy. The virulent Rabin's strain possessed a prominent capsule of 0.252 μm±0.061 μm that was diminished by in vitro growth conditions to 0.206 μm±0.076 μm. The ATCC 10400 strain capsule thickness decreased from 0.157 μm±0.043 μm to 0.117 μm±0.043 μm after 10 in vitro passages. The virulent Rabin's strain capsule was significantly thicker than the avirulent ATCC 10400 strain under all growth conditions. Rabin's strain, regardless of pre-challenge growth conditions or dose (high dose 10(7) or low dose 10(2)), was able to kill lobsters in 7 days at 15°C. ATCC 10400 strain, regardless of pre-challenge growth conditions, killed lobster only at high doses (10(7)) with varying median time to death of ∼15 days, while at low doses (10(2)) all lobsters survived and no bacteria were present after 42 days. This work demonstrates the importance of the thickness of the A. viridans capsule to virulence in the American lobster.
authors.affiliation: AVC Lobster Science Centre, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada; Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada. Electronic address: fclark@upei.ca.
authors.forename: K Fraser
authors.initials: KF
authors.lastname: Clark
authors.affiliation: Electron Microscopy Laboratory, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada. Electronic address: wadowska@upei.ca.
authors.forename: Dorota
authors.initials: D
authors.lastname: Wadowska
authors.affiliation: AVC Lobster Science Centre, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada; Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada. Electronic address: sgreenwood@upei.ca.
authors.forename: Spencer J
authors.initials: SJ
authors.lastname: Greenwood
mesh_terms: D056570:Aerococcus / Q000472:pathogenicity* / Q000648:ultrastructure; D000818:Animals; D016667:Bacterial Capsules / Q000502:physiology*; D060467:Disease Resistance; D054884:Host-Pathogen Interactions; D008121:Nephropidae / Q000276:immunology / Q000382:microbiology*; D014774:Virulence
keywords: Aerococcus viridans var. homari; Bacterial virulence; Crustacean immunology; Gaffkemia; Lobster