The A-layer influences the susceptibility of Aeromonas salmonicida to antibacterial peptides

Identification of a Novel Cathelicidin Gene in the Rainbow Trout,Oncorhynchus mykiss

“…The results in this study showed that production of a capsule did not affect susceptibility to the rtCATH_1 (R151-V186) peptide, since the MICs for the two capsulated strains of P. damsela MT1415 and L. garvieae MT2055 were lower than those for the noncapsulated strains. In the case of A-layer production, A. salmonicida strains with an A layer were shown previously to be less susceptible to cecropins B and P1 (17), and a similar conclusion was made regarding resistance to the rtCATH_1(R151-V186) peptide, where the MIC against the A-layer-positive strain MT423 was higher than that to the A-layer-negative strain MT004.…”

“…Bacteria can evolve different strategies to resist bactericidal agents. For example, producing ␤-lactamase to destroy some antibiotics (6), secreting an outer capsule to prevent phagocytosis by host leukocytes (27), or producing an A layer to aggregate bacteria and decrease susceptibility to antimicrobial peptides (17). The results in this study showed that production of a capsule did not affect susceptibility to the rtCATH_1 (R151-V186) peptide, since the MICs for the two capsulated strains of P. damsela MT1415 and L. garvieae MT2055 were lower than those for the noncapsulated strains.…”

“…Nine field isolates of fish pathogens were provided by FRS Marine Laboratory, Aberdeen, United Kingdom. Aeromonas salmonicida A-layer-negative avirulent strain MT004 and the A-layer-positive virulent strain MT423 (17) were isolated from rainbow trout. Photobacterium damselae subsp.…”

Isolation of Aeromonas salmonicida subspecies salmonicida from Lake Whitefish (Coregonus clupeaformis) inhabiting Lakes Michigan and Huron

“…Colonies of A. salmonicida salmonicida from lake whitefish were deep blue on CBBA, a differential medium for distinguishing strains of A. salmonicida salmonicida that possess an additional layer associated with the external cellular membrane (Udey 1982). This 50 kDa protein is considered an important virulence factor, as it contributes to survival of the bacterium within host macrophages (Daly et al 1996), promotes bacterial penetration and adhesion, inhibits complement-mediated lysis (Hiney and Oliver 1999), and interferes with a number of antibacterial peptides (Henry and Secombes 2000). Therefore, the presence of the surface 50 kDa protein in the isolates underscores their potential pathogenicity to lake whitefish in the Great Lakes basin.…”

Discovery and characterization of two types of liver-expressed antimicrobial peptide 2 (LEAP-2) genes in rainbow trout

“…After 1-week acclimatization, fish were injected intraperitioneally with an avirulent strain (MT004) of the salmonid pathogen Aeromonas salmonicida (Henry and Secombes, 2000) at a dose of 2 Â 10 7 bacteria (suspended in 100 ml PBS) per fish. Every two days post-injection, three fish in each group were killed and tissues (gill, head kidney, intestine, liver, skin, spleen) were removed and placed in TRIzol Reagent (Invitrogen, UK) and kept at À80 8C until use.…”