Proteinaceous exotoxins of shrimp-pathogenic isolates of Vibrio penaeicida and Vibrio nigripulchritudo

Abstract

The pathogenicity of two V. penaeicida strains, AM101 and KH-1, with different geographic origin, and V. nigripulchritudo strain AM102, were investigated in juvenile blue shrimp species Litopenaeus stylirostris. Alive bacteria and protein fractions (PFs) obtained from cell-free supernatants (CFS) were used in experimental challenges. Strains AM102, AM101, and KH-1 produced respectively 60, 54 and 12% mortality at 96 h after infection using 10 4 cfu mL -1 of bacterial suspension. Exocellular toxin-like factors were evidenced in CFS from the New Caledonian strains (AM102 and AM101) but not in the Japanese strain (KH-1). At 48 h post injection of each CFS, mortality rates were respectively 96, 98 and 5% when these strains were cultivated at 20°C, whereas only 0, 16 and 5% mortality rates were observed when these strains were cultivated at 30ºC. Clear differences in pathogenicity between both V. penaeicida strains of distinct geographic origin (AM101 and KH-1) were thus emphasized. Protein fractions were obtained from CFS of all the strains tested in this study and cultivated at 20°C, by ammonium sulfate precipitation. Whatever the used strain, significantly higher mortalities were produced with PFs obtained with 0-40% of ammonium sulfate saturation, in respect to those produced with PFs60 and PFs80. Shrimp injected with PFs40 from strains AM102, AM101 and KH-1, and at a 20-µg org -1 dose produced respectively 100, 90 and 60% mortality 46 h after the challenge. The strain AM101 showed a median lethal dose of approximately 5 µg protein org -1 (1-1.25 µg protein g -1 body weight) 59 h after injection. The PFs40 from New Caledonian strains were found sensitive to heating and proteinase K treatments, reinforcing thus the hypothesis of their proteinaceous nature. Surprisingly, PFs40 from each bacterial strain displayed similar protein bands by SDS-PAGE suggesting that the tested strains share a common exotoxic compound regardless their distinct geographic origin or species.Key words: Vibrio penaeicida, Vibrio nigripulchritudo, Litopenaeus stylirostris, shrimp, exotoxin, pathogenicity. ResumenLa patogenicidad de dos cepas de V. penaeicida, AM101 y KH-1, con diferente origen geográfico, y de la cepa AM102 de V. nigripulchritudo fue investigada en camarones azules juveniles de la especie Litopenaeus stylirostris. Las bacterias vivas y las fracciones proteicas (FPs) obtenidas del sobrenadante libre de células (SLC) fueron usadas en un ensayo experimental. Las cepas AM102, AM101 y KH-1 produjeron respectivamente una mortalidad de 60, 54 y 12%, 96 h después de la infección al usar una suspensión bacteriana de 10 4 ufc mL -1 . Factores tipo toxina exocelular fueron evidenciados en los SLC de las cepas de Nueva Caledonia (AM102 y AM101) pero no en la cepa japonesa (KH-1). A 48 h post-inyección de cada SLC, el porcentaje de mortalidad fue respectivamente de 96, 98 y 5% cuando estas cepas fueron cultivadas a 20°C, mientras que sólo 0, 16, y 5% de mortalidad fue observado cuando las cepas fueron cultivadas a 30°C. Se observ...

Effluents of Shrimp Farms and Its Influence on the Coastal Ecosystems of Bahía de Kino, Mexico

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Seasonal variation in parasite infection patterns of marine fish species from the Northern Wadden Sea in relation to interannual temperature fluctuations

“…The occurrence of potentially pathogenic strains from the family Vibrionaceae is highly correlated with temperature, leading to increased virulence and the occurrence of emerging agents in warmer waters (Thompson et al, 2004;Vezzulli et al, 2010). Beside Vibrio splendidus, we detected other strains of potential pathogens of fish (Listonella anguillarum), crustaceans (V. penaeicida) and bivalves (Vibrio tapetis), which were associated with mass mortality events in some cases (Allam et al, 2002;Aguirre-Guzman et al, 2003;Planas et al, 2005;Pernet et al, 2012). Optimal growth temperature is not known for most of the bacterial species here, but vibriosis in fish tends to occur at water temperatures above 15°C (Frans et al, 2011).…”