Epidemiology of arcobacter-related spp. In shellfish exposed to marine and brackish water with different levels of fecal pollution

Identifier:  TDX:2990

Handle: https://hdl.handle.net/20.500.11797/TDX2990

Authors:  Salas Massó, Núria

Abstract:
The genus Arcobacter, which recently has been divided into 7 new genera, comprises species that have been considered zoonotic agents and emergent pathogens. Arcobacter-related species have been recovered with a high positivity from seafood, posing a risk for the consumer as they are consumed raw or slightly cooked. In this thesis, the relationship between these bacteria and shellfish exposed to water with different levels of fecal pollution has been studied. A new approach, for improving the recovery of Arcobacter-related genera from marine and brackish environments was developed and consisted on the supplementation of Arcobacter-CAT broth with 2.5% NaCl and posterior culture in marine agar. The correlation between the levels of Escherichia coli and Arcobacter was also examined in shellfish and their surrounding water, showing positive results. However, when shellfish were harvested from water with a temperature above 26.2ºC, E. coli would fail to predict the presence of these pathogens. The distribution of Arcobacter-related genera within the tissues of mussels and oysters showed that the intervalval liquid was the compartment with higher prevalence of Arcobacter. Depuration of E. coli, A. butzleri and M. molluscorum in mussels and oysters under different bacterial loads and in two seasons (summer and winter) was analyzed. The efficacy of the conventional depuration process may not fully eliminate Arcobacter from shellfish and, probably, it is a temperature dependent process. A viable qPCR method for the detection of viable Arcobacter spp. cells in different shellfish matrixes was developed with a satisfactory inhibition of DNA amplification from dead cells in 85% of the Arcobacter species tested. As results of all these experiments, together with the use in parallel of the NaCl.enriched and non-enriched approaches, the isolation and description of seven new species belonging to four new different genera was performed.