Nineteen Salmonella strains were isolated from 5,907 randomly selected mussel samples during a monitoring programme for the presence of Salmonella in shellfish in Galicia, north-west Spain (2012–16). Serovars, sequence type and antimicrobial resistance genes were determined through genome sequencing. Presence of the mcr-1 gene in one strain belonging to serovar Rissen and ST-469 was identified. The mcr-1 gene had not been isolated previously in environmental Salmonella isolated from mussels in Spain.

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Due to the rapid elimination of bacteria through normal behaviour of filter feeding and excretion, the decontamination of hazardous contaminating bacteria from shellfish is performed by depuration. This process, under conditions that maximize shellfish filtering activity, is a useful method to eliminate microorganisms from bivalves. The microbiota composition in bivalves reflects that of the environment of harvesting waters, so quite different bacteriomes would be expected in shellfish collected in different locations. Bacterial accumulation within molluscan shellfish occurs primarily in the hepatopancreas. In order to assess the effect of the depuration process on these different bacteriomes, in this work we used 16S RNA pyrosequencing and metagenome prediction to assess the impact of 15 h of depuration on the whole hepatopancreas bacteriome of mussels collected in three different locations.

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Shiga toxin‐producing Escherichia coli are a known cause of serious illnesses, and a major public health concern. The coastal environment is the receptacle of agricultural and urban wastewater effluents, thus STEC can be present. In the current study their occurrence and prevalence in mussels (Mytilus galloprovincialis) cultured in the southern Rias of Galician was assessed. This region is interesting due to its economic importance as Galicia produces the 98% of the mussels cultured in Spain, being this country the third world producer. From June 2012 until September 2013, 241 mussel samples were collected, being 112 positive for eae and 17 also positive for stx1,2. An increase was observed in the winter months for both genes, which seemed correlated with a generalized decrease in water salinity. Serotype O157:H7 was not detected, but one isolate resulted resistant to six antibiotics, denoting the presence of multidrug resistant bacteria in this área. Practical applications A critical step for adequate risk assessments is the evaluation of potential threats. In this sense, very few microbiological parameters are analyzed in bivalve molluscs, being many human pathogens not assayed. Shiga toxin‐producing Escherichia coli was detected for the first time in mussels harvested in Galicia, a region of critical importance worldwide for the mussel industry. This study highlights that additional studies to better characterize the microbial populations of this important region are still needed, and furthermore, that measures to control microbial pathogens, such as depuration, must not be taken lightly.