SUMMARY: The pathobiological activities and of live cells and extracellular products (ECP) of eleven strains of different origin were examined. Infectivity trials showed that did not possess strict host specificity since the majority of the isolates were virulent for gilthead seabream, rainbow trout and turbot, with LD values ranging between 10 and 10 live cells. However, none of the strains tested were pathogenic for mice (LD > 10 cells). In addition, the ECP were strongly toxic for fish (LD ranging from 1.0 to 4.6 μg protein per g fish), which clearly demonstrates their important role in the pathogenesis of pasteurellosis. All the ECP samples were cytotoxic for fish and homoiothermic cell lines, possessed notable phospholipase activity and displayed haemolytic activity for sheep, salmon and turbot erythrocytes (but not for trout erythrocytes). However, the production of proteolytic enzymes differed among the strains. Although no strain displayed elastase activity, five isolates (the Japanese and Italian strains) hydrolysed casein and gelatin. All these biological activities and were lost after heat treatment (100 °C for 10 min). The general enzymic patterns of both live cells and ECP evaluated by the API-ZYM system also revealed some variation among the isolates. Generally, whole cells showed a wider range of enzymic activities than ECP. The results presented here are important for the selection of strains in the development of effective polyvalent pasteurellosis vaccines containing both whole cells and ECP.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error