An overview of 20 years of studies on the prevalence of human enteric viruses in shellfish from Galicia, Spain.

Galicia (NW Spain) has 1490 km of coastline, and its particular topography, characterized by the presence of fiord-like inlets, called rías, with an important primary production, makes this region very favourable for shellfish growth and culture. In fact, Galicia is one of the most important mussel producers in the world. Due to its proximity to cities and villages and the anthropogenic activities in these estuaries, and despite the routine official controls on the bivalve harvesting areas, contamination with material of faecal origin is sometimes possible but, current regulation based on Escherichia coli as an indicator micro-organism has been revealed as useful for bacterial contaminants, this is not the case for enteric viruses. The aim of this review is to offer a picture on the situation of different harvesting areas in Galicia, from a virological standpoint. A recompilation of results obtained in the last 20 years is presented, including not only the data for the well-known agents norovirus (NoV) and hepatitis A virus (HAV) but also data on emerging viral hazards, including sapovirus (SaV), hepatitis E virus (HEV) and aichivirus (AiV). Epidemiological differences related to diverse characteristics of the harvesting areas, viral genotype distribution or epidemiological links between environmental and clinical strains will also be presented and discussed. The presentation of these historical data all together could be useful for future decisions by competent authorities for a better management of shellfish growing areas.

First isolation of Vibrio tapetis and an atypical strain of Aeromonas salmonicida from skin ulcerations in common dab (Limanda limanda) in the North Sea.

Skin ulcerations rank amongst the most prevalent lesions affecting wild common dab (Limanda limanda) with an increase in prevalence of up to 3.5% in the Belgian part of the North Sea. A complex aetiology of these ulcerations is suspected, and many questions remain on the exact factors contributing to these lesions. To construct the aetiological spectrum of skin ulcerations in flatfish, a one-day monitoring campaign was undertaken in the North Sea. Fifteen fish presented with one or more ulcerations on the pigmented and/or non-pigmented side. Pathological features revealed various stages of ulcerations with loss of epidermal and dermal tissue, inflammatory infiltrates and degeneration of the myofibers bordering the ulceration, albeit in varying degrees. Upon bacteriological examination, pure cultures of Vibrio tapetis were retrieved in high numbers from five fish and of Aeromonas salmonicida in one fish. The V. tapetis isolates showed cross-reactivity with the sera against the representative strain of serotype O2 originating form a carpet-shell clam (Ruditapes descussatus). Moreover, the A. salmonicida isolates displayed a previously undescribed vapA gene sequence (A-layer type) with possible specificity towards common dab. Further research is necessary to pinpoint the exact role of these agents in the development of skin ulcerations in common dab.

Low prevalence of Aichi virus in molluscan shellfish samples from Galicia (NW Spain).

AIMS: The aim of this study was to detect and quantify Aichi virus (AiV) in shellfish from three estuaries in Galicia, the main producer of molluscs in Europe. METHODS AND RESULTS: A total of 249 shellfish samples were analysed using a reverse transcription-quantitative PCR procedure. AiV was detected in 15 of 249 (6·02%) samples. Ría de Ares-Betanzos showed the highest prevalence (11·1%), followed by Ría do Burgo (3·7%) and Ría de Vigo, (2·56%). AiV quantifications ranged from nonquantifiable (under the limit of quantification of the method) to 6·9 × 103 RNAc per g DT, with a mean value of 1·9 × 102 RNAc per g DT. CONCLUSION: Results obtained indicated that the prevalence of this enteric virus in the studied area is considerably lower than those of other enteric viruses, such as Norovirus, Sapovirus, HAV or HEV. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that detects the presence of AiV in shellfish from authorized harvesting areas in Spain. Further studies with clinical samples are needed to determine the potential risk of AiV for human health in Galicia.

Molecular epidemiology of norovirus from patients with acute gastroenteritis in northwestern Spain.

The high incidence of norovirus (NoV) infections seems to be related to the emergence of new variants that evolved by genetic drift of the capsid gene. In this work, that represents a first effort to describe the molecular epidemiology of NoV in the northwest of Spain, a total of eight different NoV genotypes (GII.1, GII.3, GII.4, GII.6, GII.7, GII.12, GII.13, GII.14) were detected. The major genotypes observed were GII.4 (45·42%) and GII.14 (34·9%), being detected in all age groups. In addition, and although most of GII.4 sequences belonged to 2006b (7·2%) and 2010 (50·35%) variants, the presence of new NoV variants was observed. Phylogenetic analysis revealed that a high number of GII.4 sequences (35·24%) could be assigned to the newly emerging Sydney 2012 variant, even during late 2010. The high prevalence of NoV GII.14 observed in this study may indicate the emergence of this genotype in Spain.

Vibrio tapetis isolated from vesicular skin lesions in Dover sole Solea solea.

Vibrio tapetis is primarily known as the causative agent for brown ring disease in bivalves, although it has been isolated from cultivated fish during mortalities on farms. Here we describe the first isolation of V. tapetis from wild-caught and subsequently captive-held Dover sole Solea solea. Pathological features consisted of multifocal circular greyish-white skin discolourations evolving into vesicular lesions and subsequent ulcerations on the pigmented side. On the non-pigmented side, multiple circular lesions-white at the center and red at the edges-were evident. Histological examination of the vesicular lesions revealed dermal fluid-filled spaces, collagen tissue necrosis and a mixed inflammatory infiltrate, with large numbers of small rod-shaped bacteria. In the deep skin lesions, loss of scales and dermal connective tissue, with degeneration and fragmentation of the myofibres bordering the ulceration, were noted. Serotyping, DNA-DNA hybridization and REP- and ERIC-PCR techniques showed that the retrieved isolates displayed a profile similar to the representative strain of genotype/serotype O2 which originally was isolated from carpet-shell clam Venerupis decussata and to which isolates obtained from wedge sole Dicologoglossa cuneata were also closely related.

Occurrence and fate of CECs (OMPs, ARGs and pathogens) during decentralised treatment of black water and grey water.

Decentralised wastewater treatment is becoming a suitable strategy to reduce cost and environmental impact. In this research, the performance of two technologies treating black water (BW) and grey water (GW) fractions of urban sewage is carried out in a decentralised treatment of the wastewater produced in three office buildings. An Anaerobic Membrane Bioreactor (AnMBR) treating BW and a Hybrid preanoxic Membrane Bioreactor (H-MBR) containing small plastic carrier elements, treating GW were operated at pilot scale. Their potential on reducing the release of contaminants of emerging concern (CECs) such as Organic Micropollutants (OMPs), Antibiotic Resistance Genes (ARGs) and pathogens was studied. After 226 d of operation, a stable operation was achieved in both systems: the AnMBR removed 92.4 ± 2.5 % of influent COD, and H-MBR removed 89.7 ± 3.5 %. Regarding OMPs, the profile of compounds differed between BW and GW, being BW the matrix with more compounds detected at higher concentrations (up to µg L-1). For example, in the case of ibuprofen the concentrations in BW were 23.63 ± 3.97 µg L-1, 3 orders of magnitude higher than those detected in GW. The most abundant ARGs were sulfonamide resistant genes (sul1) and integron class 1 (intl1) in both BW and GW. Pathogenic bacteria counts were reduced between 1 and 3 log units in the AnMBR. Bacterial loads in GW were much lower than in BW, being no bacterial re-growth observed for the GW effluents after treatment in the H-MBR. None of the selected enteric viruses was detected in GW treatment line.

Identification and virulence of Aeromonas dhakensis, Pseudomonas mosselii and Microbacterium paraoxydans isolated from Nile tilapia, Oreochromis niloticus, cultivated in Mexico.

AIMS: To identify bacterial pathogens of diseased NiIe tilapia Oreochromis niloticus and determine their virulence. METHODS AND RESULTS: Sixteen bacterial isolates were recovered from diseased Nile tilapias (O. niloticus) reared in floating cages in Adolfo Lopez Mateos (ALM), Sanalona and Dique IV dams in Sinaloa, Mexico, from February to May 2009. The bacterial isolates were identified by phenotypic and molecular (rep-PCR and 16S rRNA sequencing) methods and were mostly isolated from the kidneys and the brain of tilapias. Bacterial cells and extracellular products (ECPs) of strains were characterized and used in experimental infections with sole Solea vulgaris and Mozambican tilapia Oreochromis mossambicus. The fish challenged with Aeromonas dhakensis sp. nov. comb nov, Pseudomonas mosselii and Microbacterium paraoxydans (3·1 × 10(6)  CFU g(-) 1) exhibited mortality between 40 and 100% starting at 6 h postinoculation. The ECPs displayed gelatinase, haemolytic and cytotoxic activity, causing the total destruction of the HeLa cell lines. CONCLUSIONS: Aeromonas dhakensis and Ps. mosselii were virulent to O. mossambicus, whereas Mic. paraoxydans displayed virulence to S. vulgaris. SIGNIFICANCE AND IMPACT OF THE STUDY: This the first time that Aeromonas dhakensis and Ps. mosselii are reported as pathogens to tilapia and Mic. paraoxydans was isolated from fish; then, these fish pathogens could be a threat to farmed Nile tilapia in Mexico.

Two-dimensional proteome reference map of Vibrio tapetis, the aetiological agent of brown ring disease in clams.

AIMS: Vibrio tapetis is the etiological agent of brown ring disease (BRD) in clams, one of the most threatening diseases affecting this commercially important bivalve. In this study we have constructed a proteome reference map of the V. tapetis type strain CECT 4600(T). METHODS AND RESULTS: Eighty-two proteins, consistently present in all 2D-gels, were identified by mass spectrometry or by de novo sequencing. The majority of the proteins identified (66%) belonged to four COG categories: 'Carbohydrate transport and metabolism', 'Post-translational modification, protein turnover and chaperones', 'Energy production', and 'Amino acid transport and metabolism'. Glyceraldehyde-3-phosphate dehydrogenase, enolase, fructose-bisphosphate aldolase, phosphoglycerate kinase. molecular chaperones Dnak and GroEL, alkyl hydroperoxide reductase, peptidyl-prolyl cis-trans isomerase B and factor Tu, were identified among the 20 most abundant proteins. A comparison of this reference map with that obtained for the V. tapetis strain GR0202RD, with different origin and pathophysiological characteristics, was performed. CONCLUSIONS: Under the culture conditions employed in this study, glucose degradation is one of the major pathways for energy production in Vibrio tapetis. In addition, the two strains studied, although with remarkable differences at genetic and pathophysiological levels, showed a high similarity under laboratory conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The results obtained here can be considered as a first step to gather valuable information on protein expression, related not only to diverse cellular functions and regulation but also to pathogenesis and bacterium-host interactions in the disease process.

Serological and molecular heterogeneity among Yersinia ruckeri strains isolated from farmed Atlantic salmon Salmo salar in Chile.

We investigated 11 strains of Yersinia ruckeri, the causative agent of enteric redmouth disease (ERM), that had been isolated from Atlantic salmon Salmo salar L. farmed in Chile and previously vaccinated against ERM. Phylogenetic analysis of the 16S rRNA gene sequences confirmed the identification of the salmon isolates as Y. ruckeri. A comparative analysis of the biochemical characteristics was made by means of traditional and commercial miniaturised methods. All studied isolates were motile and Tween 80 positive, and were identified as biotype 1. In addition, drug susceptibility tests determined high sensitivity to sulphamethoxazole/trimethroprim, oxytetracycline, ampicillin and enrofloxacin in all isolates. Serological assays showed the presence of O1a, O1b and O2b serotypes, with a predominance of the O1b serotype in 9 strains. Analysis of the lipopolysaccharide profiles and the correspondent immunoblot confirmed these results. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the outer membrane proteins revealed that all Chilean strains had profiles with a molecular weight range between 34 and 55 kDa, with 3 distinct groups based on differences in the major bands. Genotyping analyses by enterobacterial repetitive intergenic consensus (ERIC-) and repetitive extragenic palindromic (REP-)PCR techniques clearly indicated intraspecific genetic diversity among Chilean Y. ruckeri strains.

Molecular intraspecific characterization of Photobacterium damselae ssp. damselae strains affecting cultured marine fish.

AIMS: The aim of this study was to analyse the intraspecific variability of Photobacterium damselae ssp. damselae strains isolated from different cultured marine fish species using molecular typing methods. METHODS AND RESULTS: Twenty P. damselae ssp. damselae strains isolated from marine fish species were used in this study. Phenotypic characterization of the strains was carried out using standard microbiological methods. Genetic characterization was conducted using three PCR-based methods [random amplified polymorphic DNA (RAPD), enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) and repetitive extragenic palindromic-PCR (REP-PCR)]. Dice coefficient and the unweighted pair group method with average linkage were used for numerical analyses of banding patterns. At phenotypic level, the strains analysed showed seven different profiles, which could not be related to the host fish species, geographic area or outbreak of disease. Isolates were grouped into nine and eight clusters using the RAPD technique with primers 5 and 4, respectively. In both cases, the main cluster grouped 45% of strains. The techniques ERIC-PCR and REP-PCR were more discriminatory, both resulting in 14 different clusters, which grouped 15-20% of the isolates. CONCLUSIONS: In this study, the techniques tested are confirmed as good tools for molecular typing, because they allow discrimination between P. damselae ssp. damselae strains isolated within the same outbreak. In addition, ERIC-PCR and REP-PCR methods were more adequate for rapid typing of P. damselae ssp. damselae than RAPD, allowing the discrimination at strain level. SIGNIFICANCE AND IMPACT OF THE STUDY: The results, in agreement with previous studies, confirmed the high intraspecific variability among isolated P. damselae ssp. damselae strains at both phenotypic and genetic levels. This suggests the existence of different clonal lineages that coexist in the same geographic area, within a short period of time (2-3 years). The discrimination at strain level can be useful to study the traceability of infections.

Genotyping of hepatitis A virus detected in bivalve shellfish in Galicia (NW Spain).

Hepatitis A virus (HAV) represents a significant public health problem due to its high persistence in the environment and its transmission through contaminated water and food. Bivalve shellfish are filter feeders that can bioaccumulate human pathogens found in contaminated waters, their consumption being a potential cause of hepatitis A outbreaks. In this work, cultured and wild bivalve shellfish from the Ría de Vigo (Galicia, NW Spain) were analysed for the presence and genotyping of HAV. A total of 160 shellfish samples were collected between March 2004 and December 2006, including 68 samples from cultured mussels (Mytilus galloprovincialis), 30 from wild clams (Rupitapes decussatus), 31 from wild cockles (Cerastoderma edule) and 31 from wild mussel. HAV detection, carried out by quantitative RT-PCR, was positive for 29 (42.6%) cultured and 40 (43.5%) wild samples, with levels ranging from 3.1 x 10(2) and 1.4 x 10(10) RNA copies/g of shellfish digestive tissue. The phylogenetic analysis of VP1-P2A and VP3-VP1 regions, separately or as concatenated sequences, revealed that all HAV strains analysed belong to subgenotype IB. These results indicate a high prevalence of this subgenotype in the area studied.

Experimental Pseudomonas anguilliseptica infection in turbot Psetta maxima (L.): a histopathological and immunohistochemical study.

Experimental infection with Pseudomonas anguilliseptica was performed both by intraperitoneal (i.p.) and bath route on juvenile turbot (Psetta maxima) in order to evaluate the pathology induced. Turbot was found to be sensitive to i.p. challenge (1.7x10(6) CFU/fish) but no to bath exposure. The i.p. challenge induced septicaemic infection and mortality. Externally, moribund fish showed distended abdomen and pale areas at day 9. The gross pathological internal signs present were abundant ascitic fluid in the peritoneal cavity, pale and enlarged spleen, pale and friable liver, and congestive and dilated gut with yellowish exudates. On histopathological examination, bacterial invasion was common in all the tissues studied but the most prominent pathological changes were observed in gut, spleen and kidney after 7 day with features of necrosis. The immunohistochemical findings support the widespread localization of the bacteria after the i.p. injection since the P. anguilliseptica was detected in spleen from day 1 post injection, in liver, kidney and gut from day 4, in muscle from day 7 and in brain from day 9. The difficulties in infecting healthy fish by bath challenge can be explained by the opportunistic nature of this pathogen.

Genetic characterization of Streptococcus phocae strains isolated from Atlantic salmon, Salmo salar L., in Chile.

Streptococcus phocae is a beta-haemolytic bacterium frequently involved in disease outbreaks in seals causing pneumonia or respiratory infection. Since 1999, this pathogen has been isolated from diseased Atlantic salmon, Salmo salar, causing serious economic losses in the salmon industry in Chile. In this study, we used different molecular typing methods, such as pulsed-field gel electrophoresis (PFGE), randomly amplified polymorphic DNA (RAPD), enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR), repetitive extragenic palindromic PCR (REP-PCR) and restriction of 16S-23S rDNA intergenic spacer regions to evaluate the genetic diversity in S. phocae. Thirty-four strains isolated in different years were analysed. The S. phocae type strain ATCC 51973(T) was included for comparative purposes. The results demonstrated genetic homogeneity within the S. phocae strains isolated in Chile over several years, suggesting the existence of clonal relationships among S. phocae isolated from Atlantic salmon. The type strain ATCC 51973(T) presented a different genetic pattern with the PFGE, RAPD, ERIC-PCR and REP-PCR methods. However, the fingerprint patterns of two seal isolates were distinct from those of the type strain.

#EUROmicroMOOC: using Twitter to share trends in Microbiology worldwide.

Twitter is one of the most popular social media networks that, in recent years, has been increasingly used by researchers as a platform to share science and discuss ongoing work. Despite its popularity, Twitter is not commonly used as a medium to teach science. Here, we summarize the results of #EUROmicroMOOC: the first worldwide Microbiology Massive Open Online Course taught in English using Twitter. Content analytics indicated that more than 3 million users saw posts with the hashtag #EUROmicroMOOC, which resulted in over 42 million Twitter impressions worldwide. These analyses demonstrate that free Microbiology MOOCs shared on Twitter are valuable educational tools that reach broad audiences throughout the world. We also describe our experience teaching an entire Microbiology course using Twitter and provide recommendations when using social media to communicate science to a broad audience.

Complete Genome Sequence of Arcobacter sp. Strain LFT 1.7 Isolated from Great Scallop (Pecten maximus) Larvae.

Arcobacter sp. strain LFT 1.7 was isolated from great scallop (Pecten maximus) larvae. Analysis of the 16S rRNA gene sequence showed that strain LFT 1.7 formed an independent lineage in the genus Arcobacter The draft genome of LFT 1.7 was sequenced to determine the taxonomic position and ecological function of this strain.

Draft Genome Sequences of Neptuniibacter sp. Strains LFT 1.8 and ATR 1.1.

We present the draft genomes of two strains previously identified as Neptuniibacter sp. LFT 1.8 (= CECT 8936 = DSM 100781) and ATR 1.1 (= CECT 8938 = DSM 100783) isolated from larvae of great scallops (Pecten maximus) and seawater, respectively. Both strains surely constitute two novel species in this genus, with putative applications for aromatic compound degradation.

Vaccination strategies to prevent emerging diseases for Spanish aquaculture.

In recent years, three serious diseases have emerged in Spanish aquaculture. These are lactococcosis caused by Lactococcus garvieae, which is of economical importance in rainbow trout (Oncorhynchus mykiss); pseudomonadiasis caused by Pseudomonas anguilliseptica which affects gilthead seabream (Sparus aurata) and turbot (Scophthalmus maximus); and flexibacteriosis caused by Tenacibaculum maritimum which became a devastating problem in the emerging culture of sole (Solea spp). To obtain useful information for the design and development of new vaccines, antigenic characterisation of representative strains was performed. In this work we present the strategies adopted for the vaccine formulation (strains included, use of adjuvants) and administration (route, necessity of booster, etc.). The results from laboratory and/or field vaccination trials performed showed that for lactococcosis, protection lasting for five months was obtained with an oil-adjuvanted bacterin formulation. Unadjuvanted bacterin gave only a short duration of protection, which could, however, be prolonged by an antigen boost administered via the feed. A bacterin against Pseudomonas anguilliseptica gave protection for 12 weeks when tested in an experimental challenge trial in turbot. Besides the flexibacteriosis vaccine developed by our group for turbot, and due to the antigenic host-associated variability within T. maritimum, a new bacterin was developed against this bacterium to be used specifically in sole. This new bacterin, administered to sole by intraperitoneal injection, yielded RPS values of 94 % six weeks after immunization. In conclusion, these results suggest that vaccination constitutes a cost-effective method of controlling diseases that have emerged in the most important fish species being cultured in Spain.

Seasonal variation of bacterial communities in shellfish harvesting waters: preliminary study before applying phage therapy.

The recurrent emergence of infections outbreaks associated with shellfish consumption is an important health problem, which results in substantial economic losses to the seafood industry. Even after depuration, shellfish is still involved in outbreaks caused by pathogenic bacteria, which increases the demand for new efficient strategies to control the shellfish infection transmission. Phage therapy during the shellfish depuration is a promising approach, but its success depends on a detailed understanding of the dynamics of bacterial communities in the harvesting waters. This study intends to evaluate the seasonal dynamics of the overall bacterial communities, disease-causing bacterial populations and bacterial sanitary quality indicators in two authorized harvesting-zones at Ria de Aveiro. During the hot season, the total bacterial community presented high complexity and new prevalent populations of the main shellfish pathogenic bacteria emerged. These results indicate that the spring/summer season is a critical period during which phage therapy should be applied.

Pathological activities of Yersinia ruckeri, the enteric redmouth (ERM) bacterium.

The adherence and invasive capacities as well as the pathobiological activities exhibited by Yersinia ruckeri were examined. Although adhesive ability was dependent on the cell-line employed, all the strains showed moderate adhesion and invasiveness in the salmon cell-line CHSE-214. With regard to the extracellular products (ECP) all of them were strongly toxic for fish with LD50 ranging from 2 to 9.12 micrograms protein per g fish. In addition, all the ECP samples showed caseinase, gelatinase, amylase, lipase and phospholipase activities, hydrolysed esculin and displayed hemolytic activities for trout, salmon, sheep and human erythrocytes. Heat treatment (100 degrees C for 10 min) caused the loss of all these biological activities except the hydrolysis of gelatin. On the other hand, SDS-PAGE analysis of the LPS and protein components of the ECP revealed variations among strains depending on the serotype. The lack of lethal effects of the LPS present in the ECP was also demonstrated.

Use of pulsed field gel electrophoresis to size the chromosome of the bacterial fish pathogen Yersinia ruckeri.

Field inversion gel electrophoresis (FIGE) and contour-clamped homogeneous field (CHEF) electrophoresis were used to analyse the chromosome of Yersinia ruckeri. The 8 base-pair recognition endonucleases, NotI and SfiI, generated less than 47 DNA fragments whose size and distribution were appropriate for pulsed field separation. Each isolate displayed a characteristic restriction pattern, with about 20% of bands in common. Depending on the strain used, the estimated genome size for this bacterial fish pathogen ranged from 4460 to 4770 kilobase pairs.