Evidence for Phage-induced virulence in the shrimp pathogen

Flegel, T.W., Pasharawipas, T., Owens, L., and Oakey, H.J. (2005) Evidence for Phage-induced virulence in the shrimp pathogen. In: Proceedings of the Fifth Symposium on Diseases in Asian Aquaculture (5), pp. 329-337. From: Diseases in Asian Aquaculture V, 24-28 November 2005, Gold Coast, QLD, Australia.

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Abstract

Vibrio species comprise the most frequently encountered bacterial pathogens of cultivated shrimp, and V. harveyi is amongst the most virulent. Most V. harveyi strains are luminescent on agar media and also in infected shrimp that are suffering from luminescent disease or luminous bacteriosis. However, not all isolates of V. harveyi are highly virulent. Some can be injected at high dose (10-7 -10 5 cells per g shrimp body weight) without causing shrimp mortality, while other isolates are lethal at 10 -3 per g shrimp body weight or less. In addition, virulence is often lost upon continuous subculture. Simple differentiation of virulent and avirulent isolates has not been successful, although virulence factors including various enzymes (e.g., proteases and lipases), siderophores and proteinaceous toxins have been identified. Because of this and the genetic diversity of V. harveyi, it has been suggested that virulence is acquired via mobile genetic elements. Indeed, recent work has suggested that 2 quite different bacteriophages, one from the family Myoviridae and the other from the family Siphoviridae, can change the phenotype of V.harveyi isolates from non-virulent to virulent. The host range for both bacteriophages is relatively narrow. A similar phenomenon occurs in V. cholerae, where conversion to virulence is mediated by a filamentous phage (Inovirus) from the family Inoviridae. Altogether, the current information suggests that there may be diverse groups of phages and complementary Vibrio hosts that could mediate virulence in V. harveyi and make the process quite complex. It also suggests that virulence of other Vibrio pathogens of shrimp may be influenced by bacteriophages. Thus, the use of bacteriophages for biological control of pathogenic Vibrio species in aquaculture should include environmental impact studies on the potential for transfer of virulence or antibiotic resistance genes.

Item ID: 7793
Item Type: Conference Item (Refereed Research Paper - E1)
ISBN: 974-7313-64-2
Date Deposited: 11 Jan 2010 00:33
FoR Codes: 06 BIOLOGICAL SCIENCES > 0605 Microbiology > 060506 Virology @ 100%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830199 Fisheries - Aquaculture not elsewhere classified @ 100%
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