In fish the ECP caused a cytotoxic response with mortahty h

In fish the ecp caused a cytotoxic response with

This preview shows page 337 - 339 out of 594 pages.

marked proteolytic and phospholipase activity. In fish, the ECP caused a cytotoxic response, with mortahty occurring 24-48 h after administration. Here, the LD50 dose for rainbow trout and striped bass was 0.4 and 4.8 |ig of protein/g offish, respectively (Baya et aL, 1992c). Serratia plymuthica Laboratory experiments revealed that the LD50 dose for rainbow trout was loMo^ cells. Moreover, such infected fish displayed discoloration and abdominal swelling (Nieto et ai, 1990) and extensive surface lesions (Austin and Stobie, 1992b). Isolates were strongly hydrophobic (Rodriguez et al, 1990); a property that may be involved in the adherence of the organism to surfaces. Yersinia intermedia It was considered that the organism was of endogenous origin, being a pathogen of cold-stressed (possibly immuno-compromised) fish (Carson and Schmidtke, 1993). Pathogenicity experiments have not been carried out.
Image of page 337
318 Bacterial Fish Pathogens Yersinia vuckevi In terms of pathogenicity to rainbow trout, Type 1 (Hagerman) is the most virulent, followed by Type 2 (O'Leary) and then Type 3 (Australian) (Bullock et ai, 1983). The LD50 dose has been established to be 3.0 x 10^ cells/ml for Type 1, 1.0 x 10^ cells/ml for Type 2 and an as yet undetermined dose for Type 3. The degree of pathogenicity of serovars IV and V needs clarification. The new biogroup described by Austin et al. (2005a) killed rainbow trout within 4 days at a dose of 10^ cells/fish. It should be emphasised that exposure to sublethal concentrations of copper, i.e. 7 |ig/l for 96 h, rendered the fish more susceptible to infection by Y. ruckeri (Knittel, 1981). Moreover, the nature of the virulence factors is incompletely understood. The role of plasmids in virulence has been indicated insofar as the more pathogenic Type 1 isolates possess a large 40-50 mDa plasmid, and some contain a smaller 20-30 mDa plasmid. The larger plasmid is absent from Type 2 cultures (Cook and Gemski, 1982; De Grandis and Stevenson, 1985). Further work is necessary, however, to resolve the precise role of this large plasmid in pathogenicity, especially as it is not thought to carry virulence factors (Guilvout et al, 1988). The O-antigen, from the LPS of serogroup Ol, has been determined to comprise a branched tetrasaccharide, with repeating units containing 2-acetamidino-2,6- dideoxy-L-galactose, 2-acetamido-2-deoxy-D-glucose and 7-acetamido-3,5,7,9-tetra- deoxy-5-(4-hydroxybutyramido)-D-glycero-L-galacto-nonulosonic acid (Beynon et al, 1994). ECP have been recovered, and demonstrated to have an LD50 of 2-9.12 |ig of protein/g of fish. The ECP has been found to contain amylase, caseinase, gelatinase, haemolytic (salmon, sheep and trout erythrocytes) lipase and phospholipase activity. A novel 47 kDa azocasein hydrolysing protease, which was produced during the end of the exponential growth phase, was recovered from culture supernatants (Secades and Guijarro, 1999). Later, a serralysin metallo-protease (= metallo-endopeptidase), termed Yrpl, which hydrolyses actin, fibrinogen, gelatin, laminin and myson (but not Type II and Type IV collagen) has been linked to pathogenicity (Fernandez et al., 2002; 2003). Also, aesculin has been attacked (Romalde and Toranzo, 1993). Adhesin
Image of page 338
Image of page 339

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