Pathogenic variability of Pasteurella piscicida during in vitro cultivation as a preliminary study for vaccine production

Abstract

During in zritro cultivation of bacteria, the pathogenetic factors may change in amount and quality. Knowledge of this variability is important in vaccine production. The pathogenic variability of Pusteurella piscicida broth culture (BC), extracellular products (ECPs) and whole cells (WC) was investigated in sea bass (Dicentrarchus labras) 2-3 g wet weight, inoculated intraperitoneally. Ten Pasteurellapiscicirla field strains isolated from fish affected by different outbreaks which occurred in Italian fish farms were used. When BC and ECPs were intraperitoneally injected, no variability in virulence was observed between strains of different geographical origin and no attenuation was registered between strains of different in oitro passages. The electrophoretic (SDS-PAGE) analysis of ECP showed evidence of only quantitative differences inside the panel of strains and between the same strain collected at different in ~i t r o cultivation times. ECPs produced from a BC incubated for 18-60 h were highly toxic. This ability was heat labile and not active when ECPs were administered by immersion. No toxic capacity was observed with WC where infection was greater with a 18-60 h incubation broth culture. Results seems to indicate that the toxic activity of Pasteurella piscicida is mostly due to ECP and not bounded to the cell.

AIP56, a novel plasmid‐encoded virulence factor of Photobacterium damselae subsp. piscicida with apoptogenic activity against sea bass macrophages and neutrophils

“…AIP56 appears as a major protein band in the electrophoretic profiles of exponential culture supernatants of virulent Phdp . It should be noted that the low complexity of the electrophoretic profiles of these supernatants is in contrast to previous studies suggesting the secretion of a highly complex mixture of different proteins by Phdp (Bakopoulos et al ., 1997; Mazzolini et al ., 1998). The larger protein complexity of the culture supernatants observed by those researchers could be explained by the fact that stationary‐phase cultures were used in those studies.…”

A secreted NlpC/P60 endopeptidase fromPhotobacterium damselaesubsp.piscicidacleaves the peptidoglycan of potentially competing bacteria

“…Although it has been suggested that Phdp remains in a cultivable form in salt water for only [4][5] days (38,39), it was also suggested that it has the ability to enter a dormant, non-cultivable but infectious state in salt water and sediment (40). With regard to the mechanisms responsible for the pathogenicity of Phdp, it was shown that extracellular products (ECPs) play a fundamental role (41,42) although among their components, only the toxin AIP56 has been identified and characterized so far (43)(44)(45)(46)(47).…”

“…(eds) Structural Bioinformatics. Methods in Molecular Biology, vol 2112.Humana, New York, NY, pp [29][30][31][32][33][34][35][36][37][38][39][40][41][42]…”

Histopathological findings after sea bass (Dicentrarhus labrax L.) exposure to extracellular products of Photobacterium damsela subsp. piscicida produced in vivo

“…Although the pathogenesis of the disease is not yet fully understood, its has been reported that the extracellular products (ECPs) of Photobacterium damsela subsp. piscicida ( Phdp ) are major virulence factors contributing to the development of the disease (Mazzolini, Fabris Ceschia, Vismara, Magni, Amadei, Passera, Danielis & Giorgetti 1998) enabling the bacterium to counteract the host's defence mechanisms (Magarinos, Toranzo & Romalde 1996).…”