Other genes encoded synthesis of O antigen Zhang et al 2000 Aeromonas jandaei

Other genes encoded synthesis of o antigen zhang et

This preview shows page 314 - 316 out of 594 pages.

goprotease A, OMP and multi-drug resistance protein. Other genes encoded synthesis of O-antigen (Zhang et al, 2000). Aeromonas jandaei Esteve (1995) and Esteve et al. (1995b) reported a high LD50 dose of ~10^ cells for eel. Possibly, the ECP activity, which was equated with production of caseinase.
Image of page 314
Pathogenicity 295 collagenase, elastase, protease, lipase and haemolysin, caused pathogenicity (Esteve et aL, 1995b). Aeromonas salmonicida The spread of the pathogen Historically, Aer. salmonicida was regarded as a risk primarily to salmonids (e.g. Mackie et al, 1930, 1933, 1935). Then, cyprinids followed by other freshwater and marine fish became recognised to be vulnerable to infection (e.g. Herman, 1968; Austin et al, 1998). Could farmed salmonids pose a realistic risk to native marine fish species? The data on this topic are confusing. Certainly, marine fish larvae have been infected with Aer. salmonicida subsp. salmonicida, with turbot regarded as being more susceptible than hahbut (Bergh et ai, 1997). Using co-habitation and injection challenges, experiments suggested that Aer. salmonicida subsp. salmonicida could be transmitted rarely from Atlantic salmon to Atlantic cod, halibut and wrasse (Hjeltnes et al., 1995). Could atypical isolates, which are appearing with increasing frequency in wild fish, pose a threat to cultured salmonids? Wiklund (1995) using an atypical isolate from ulcerated flounder concluded that there was not any risk to rainbow trout. What about the risk of transferring Aer. salmonicida from the freshwater to seawater stage of salmonids? Eggset et al. (1997) concluded that the susceptibility of Atlantic salmon to furunculosis in seawater possibly reflected the overall quality of the smolts. Pathogenicity historical aspects Although the factors conferring pathogenicity on Aer. salmonicida strains have been the subject of speculation since early in the study of the pathogen, it is only relatively recently that the details concerning pathogenesis and virulence have begun to be elucidated. The initial investigations, carried out in the 1930s, resulted in several key observations, notably that prolonged laboratory maintenance of Aer. salmonicida isolates was frequently responsible for a loss of virulence, and that histopathological examinations of infected fish suggested the occurrence of leucopenia and proteolysis in certain tissues. Among the first studies concerned with virulence mechanisms of the organism was the extensive work of the Furunculosis Committee in the U.K. (Mackie et al., 1930, 1933, 1935). This group did not detect any toxin production by Aer. salmonicida when either ultra-filtrates of broth cultures or diseased fish tissue was injected into healthy fish. Based on their failure to demonstrate toxin production, they hypothesised as a result of detailed clinical observations that the pathogenic processes caused by Aer. salmonicida could be explained by the prolific growth in the blood and tissues of its host which, in turn, interfered with blood supply resulting in anoxic cell necrosis and ultimately death. Additional evidence for a possible con-
Image of page 315
Image of page 316

You've reached the end of your free preview.

Want to read all 594 pages?

  • Spring '20
  • Bacteria, representative, gram-negative bacteria

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors