Lithium levels and lifestyle in patients with bipolar disorder: a new tool for self-management

BACKGROUND

Patients should get actively involved in the management of their illness. The aim of this study was to assess the influence of lifestyle factors, including sleep, diet, and physical activity, on lithium levels in patients with bipolar disorder.

METHODS

A multicenter study was performed. In total, 157 lithium measurements were done biweekly in a sample of 65 patients (35 women) over 6 weeks. Lifestyle, based on total sleep hours and physical activity, was assessed by actigraphy. Diet was evaluated using the Mediterranean Lifestyle Index (Medlife).

RESULTS

35.4% of patients had a normal weight. The mean Medlife score was 14.5 (± 2.5) (moderate-good adherence to Mediterranean diet). BMI, daily dose of lithium and intensity of physical activity had a combined effect on lithium levels, after adjustment for other variables. Patients who practiced intense physical exercise, who took lower doses and had a higher BMI exhibited lower levels of lithium.

CONCLUSIONS

Higher physical activity and BMI contribute to lower lithium levels. Patients should be made aware of these relationships to improve their perception of control and self-management. Lifestyle-based interventions contribute to establishing a more personalized medicine.

Children and adolescents exposed to maltreatment already exhibit epigenetic patterns suggestive of heightened low-grade inflammation

Introduction

Childhood maltreatment (CM) is one of the best described environmental risk factors for developing any psychiatric disorder, while it also confers increased odds for obesity, cardiometabolic disorders and all-cause mortality. Inflammation has been suggested to mediate the widespread clinical effects of CM. Previously, Ligthart et al. (2016) identified a polyepigenetic signature of circulating CRP levels, a measure of chronic low-grade inflammation, that has been reliably associated with a wide array of complex disorders. The study of this biomarker could dilucidate the mechanistic relationship between CM and psychiatric outcomes.

Objectives

Thus, CRP-associated epigenetic modifications were explored regarding proximal exposure to CM.

Methods

Genomic DNA was extracted from peripheral blood mononuclear cells of 157 children and adolescents (7 to 17 years old). Exposure to CM was assessed following the TASSCV criteria. Genome-wide DNA methylation was assessed by means of the EPIC array. Fifty-two out of the 58 original CRP-associated CpG sites surpassed quality control and were included in the analysis. Age, sex, psychopathological status and cell type proportions were included as covariates.

Results

DNA methylation at 12 out of 52 CpG sites (23%) was significantly associated with exposure to CM (p < .05); 8 of these associations survived correction for multiple testing (q < .05).

Conclusions

This is the first study to date to explore the relationship between childhood maltreatment and an epigenetic signature of chronic low-grade inflammation. Our findings underscore the presence of immune dysregulation early after exposure to CM; further studies are needed to assess the long-term clinical implications of this signature in psychiatric patients.

Disclosure

No significant relationships.

Altered Executive Function in Suicide Attempts

Introduction

Executive function organizes and directs behaviour but alterations in this cognitive domain can lead to inaccurate perception, interpretation and response to environmental information, which could be a risk factor for suicide.

Objectives

To explore executive function performance of depressed recent suicide attempters in comparison to depressed past suicide attempters, depressed non-attempters and healthy controls.

Methods

96 participants from the Psychiatry Department of the Araba University Hospital-Santiago were recruited as follows: 20 patients with a recent suicide attempt (<30days) diagnosed with a Major Depressive Disorder (MDD), 33 MDD patients with history of attempted suicide, 23 non-attempter MDD patients and 20 healthy controls. All participants underwent a clinical interview and neuropsychological assessment on executive function with the Wisconsin Sorting Card Test. Backward multiple regressions were performed adjusting for significant confounding variables. For group comparisons ANOVA test and Bonferroni post hoc test were performed with p<0.05 significance level.

Results

Patient groups did not differ regarding severity of depression. All patient groups performed significantly worse than healthy controls on executive function. Adjusted comparisons between patient groups indicated that recent suicide attempters had a poorer performance in this cognitive domain in comparison to both depressed lifetime attempters and depressed non-attempters (B=0.296, p=0.019 and B=0.301, p=0.028 respectively).

Conclusions

Executive function performance is altered in recent suicide attempts. As impaired executive function can be a risk factor for suicide, preventive interventions on suicide should focus on its assessment and rehabilitation.

Disclosure

No significant relationships.

Reinforcing the new diagnosis of Complex Post-Traumatic Stress disorder (CPTSD) of ICD-11: exploring the clinical outcomes in youth exposed to complex trauma

Introduction

Youth exposed to complex trauma (CT) show an increased risk of psychiatric morbidity, including a wide range of psychiatric disorders. However, to date, there is no specific diagnosis in the DSM-5 that capture the clinical complexity of these patients. Properly, the last version of the ICD-11 includes a diagnosis termed Complex Post-Traumatic Stress Disorder (CPTSD), which considers the pattern of post-traumatic stress symptoms, plus life-impairing disturbances in self-organization (emotion dysregulation, negative self-concept and interpersonal problems). Clinical research about CPTSD, especially in younger population, is still limited.

Objectives

To explore the symptomatology of CPTSD in a sample of youth exposed to CT and its association with worse clinical outcomes.

Methods

187 youth aged 7 to 17 years participated in the EPI_young_stress_project (116 with current psychiatric disorder and 71 healthy controls). CT was evaluated following the TASSCV criteria. To identify CPTSD symptomatology, we performed an exploratory factor analysis including CBCL and TEIQue items. The global level of functioning was measured by CGAS.

Results

Preliminary results pointed that youth exposed to CT showed greater internalizing (p<.001) and externalizing (p<.001) symptomatology. Regardless of their current primary diagnosis based on DSM-5, youth exposed to CT reported more CPTSD symptomatology (p<.001). Moreover, youth with CPTSD showed greater use of psychotropic drugs (p<.001), higher and longer hospitalizations (p=.002) and worse overall functioning (p<.001).

Conclusions

The inclusion of the CPTSD in future versions of mental disorders manuals should increase the implementation of early specific trauma interventions, which may improve victims’ lives and reduce the risk of worse clinical outcomes.

Disclosure

No significant relationships.

A longitudinal study of gene expression in first-episode schizophrenia; exploring relapse mechanisms by co-expression analysis in peripheral blood

Little is known about the pathophysiological mechanisms of relapse in first-episode schizophrenia, which limits the study of potential biomarkers. To explore relapse mechanisms and identify potential biomarkers for relapse prediction, we analyzed gene expression in peripheral blood in a cohort of first-episode schizophrenia patients with less than 5 years of evolution who had been evaluated over a 3-year follow-up period. A total of 91 participants of the 2EPs project formed the sample for baseline gene expression analysis. Of these, 67 provided biological samples at follow-up (36 after 3 years and 31 at relapse). Gene expression was assessed using the Clariom S Human Array. Weighted gene co-expression network analysis was applied to identify modules of co-expressed genes and to analyze their preservation after 3 years of follow-up or at relapse. Among the 25 modules identified, one module was semi-conserved at relapse (DarkTurquoise) and was enriched with risk genes for schizophrenia, showing a dysregulation of the TCF4 gene network in the module. Two modules were semi-conserved both at relapse and after 3 years of follow-up (DarkRed and DarkGrey) and were found to be biologically associated with protein modification and protein location processes. Higher expression of DarkRed genes was associated with higher risk of suffering a relapse and early appearance of relapse (p = 0.045). Our findings suggest that a dysregulation of the TCF4 network could be an important step in the biological process that leads to relapse and suggest that genes related to the ubiquitin proteosome system could be potential biomarkers of relapse.

Influence of social cognition as a mediator between cognitive reserve and psychosocial functioning in patients with first episode psychosis

BACKGROUND

Social cognition has been associated with functional outcome in patients with first episode psychosis (FEP). Social cognition has also been associated with neurocognition and cognitive reserve. Although cognitive reserve, neurocognitive functioning, social cognition, and functional outcome are related, the direction of their associations is not clear. Therefore, the main aim of this study was to analyze the influence of social cognition as a mediator between cognitive reserve and cognitive domains on functioning in FEP both at baseline and at 2 years.

METHODS

The sample of the study was composed of 282 FEP patients followed up for 2 years. To analyze whether social cognition mediates the influence of cognitive reserve and cognitive domains on functioning, a path analysis was performed. The statistical significance of any mediation effects was evaluated by bootstrap analysis.

RESULTS

At baseline, as neither cognitive reserve nor the cognitive domains studied were related to functioning, the conditions for mediation were not satisfied. Nevertheless, at 2 years of follow-up, social cognition acted as a mediator between cognitive reserve and functioning. Likewise, social cognition was a mediator between verbal memory and functional outcome. The results of the bootstrap analysis confirmed these significant mediations (95% bootstrapped CI (-10.215 to -0.337) and (-4.731 to -0.605) respectively).

CONCLUSIONS

Cognitive reserve and neurocognition are related to functioning, and social cognition mediates in this relationship.

First bipolar episode and functionality: Relation with depressive symptoms and inflammation levels

Introduction

It is important to make an early and effective intervention from the first bipolar episode. The presence of depressive symptoms in the course of a manic episode could influence negatively the evolution and the prognosis of the patient. Inflammation and oxidative stress are also related with functionality.

Objectives

To explore the relationship between depressive symptoms during a first episode of mania, inflammatory parameters and patient functionality during the follow-up.

Method

We included in the study 92 are patients with a first manic episode and 92 matched healthy controls. We compared 13 inflammatory/oxidative stress parameters measured at baseline (TFNα, IL6, PGE2, MCP1, TBARS, NO2, SOD, CAT, GSHTOT, GSSG, GSHfree, GPx, TAS) between both groups. Between patients, 46 presented pure mania (PM) (no depressive symptoms) and 46 mixed mania (MM) (with depressive symptoms). We explored the influence of inflammatory factors in functionality, exploring differences between PM and MM. To measure patients’ general functioning one year after illness onset, we used the Functional Assessment Short Test (FAST).

Results

We found significant differences in TFNα, MCP1 and TBARS (higher in patients) and in SOD, GSHtot, GSSG, GSHfree, GPx and TAS levels (lower in patients). Only In MM group, there was a significant influence of SOD and GSHfree in FAST scores suggesting that a higher antioxidant levels at baseline the patient functionality improves one year after.

Conclusions

Some parameters of oxidative stress at baseline are related with patient's functionality one year after the first episode of mania, but only when mania debuts with depressive symptons simultaneously.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Monitoring of the novel rabbit haemorrhagic disease virus type 2 (GI.2) epidemic in European wild rabbits (Oryctolagus cuniculus) in southern Spain, 2013-2017

Rabbit hemorrhagic disease (RHD) is a highly infectious disease in European rabbits (Oryctolagus cuniculus), caused by a virus belonging to the genus Lagovirus (RHDV; family Caliciviridae). In 2010, a new genotype of RHDV (RHDV2 or RHDVb, currently designated GI.2) emerged in France, affecting both domestic rabbits, even those vaccinated for the classical RHDV genotypes (currently designated GI.1) and wild rabbits. GI.2 was subsequently identified in other European countries. The aim of the present study was to monitor the GI.2 epidemic in wild rabbits in Andalusia (southern Spain) during the period 2013-2017. At the beginning of summer 2013, high mortalities were detected in wild rabbit populations in southern Spain. A total of 96 affected hunting or protected areas were surveyed. The first outbreak was observed on June 2013. The number of outbreaks sharply increased in 2013 and 2014, with a decreasing trend being observed during the following years. The spatial distribution of GI.2 was not homogeneous, since most of the detected outbreaks were concentrated in the western part of Andalusia. The outbreaks peaked in winter and spring and have been detected in the last five consecutive years, which suggests endemic circulation of GI.2 in wild rabbit populations in Spain. A total of 190 dead rabbits from 87 of the 96 areas surveyed were collected during the study period. Mortality affected rabbits of different age classes, including kittens. RT-PCR confirmed the presence of GI.2 RNA in the livers of 185 of the 190 (97.4%) rabbits. Phylogenetic analysis performed on eleven samples collected in different provinces of Andalusia between 2013 and 2017, showed high nucleotide identity with GI.2 strains Spain, France and Portugal. The results constitute an important step in understanding of the emergence and spread of GI.2 in this country and will provide valuable information for the development of surveillance programs in Europe.

Telemedicine and bipolar disorder

Show the efficacy of an innovate telemedicine psyeducational invention based on a psychoeducational intervention treatment with a group of bipolar patients.

Objetives

To assess the efficacy of an innovate telemedicine psyeducational treatment (TPT) based on a psychoeducational intervention (21 sessions) with an additional support through telemedicine which has 12 videos versus treatment as usual (TAU) based on psychiatry reviews. Specifically, the objective was to evaluate patients’ efficacy of psyeducational treatment with telemedicine (TPT) in the fuctionalitity, depressive symptoms and manic symptoms.

Methods

Thirty-eight patients with bipolar disorder were included in the study and randomly distributed in the two groups. The telemedine treatment is performed through a www.puedoser.es web platform provided by Astra Zeneca. In the web platform is available forums, emails and digital-course with the sessions worked as a reminder. In order to assess the effectiveness of treatments, FAST scale was administered at baseline and 6 months after the intervention. To obtain the results we used coparative data analysis.

Results

In patients, we found a low daily functionality. The main issues were: interpersonal cognitive area (t = –2.611; P = 0.014) and interpersonal-area (t = –2.617; P = 0.014). We found, at baseline, that TPT group had worse overall results in daily functionality (t = –2.876; P = 0.008). After intervention, there is an improvement in the daily functionality of the TPT group. This improvement occurred in cognitive area (z = –3.24; P < 0.001), leisure area (z = –1.85; P = 0.065) and interpersonal area (z = –1.72; P = 0.086).

Conclusions

The psychoeducational program combined with telemedicine shows to be more effective than TAU in the improvement of general patient functioning in bipolar disorder patients.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Evolution of inflammatory dysregulation and oxidative stress in patients with first episode of mania

Introduction

Recent studies have focused on the imbalance in inflammatory and antioxidant pathways as possible causes of the underlying neurodegenerative processes in bipolar disorder. Thus, the study of these pathways in first episodes of mania (FEM) can increase knowledge about this issue.

Aim

To compare plasma concentrations of pro-inflammatory (MCP-1, PGE2, TNFα) and oxidative parameters (TAS, NO2 and TBARS) between controls and FEM patients and to analyze the evolution of these parameters in patients from baseline to 6 months assessment time.

Methods

This study included 44 FEM patients and 79 healthy controls, aged 18 to 40. Blood samples were available for controls at baseline and for patients at baseline and 6 months after. TAS and TBARS were measured using non-EIA assay kits, N02 was measured with Griess method and PGE2, MCP-1 and TNFα with ELISA kits.

Results

At baseline, TAS was significantly lower in patients than in controls and TBARS, MCP-1 and TNFα were significantly higher in patients. Among patients, TAS and MCP1 were lower at 6 months than at the illness onset and PGE2 and NO2 were significantly higher than at baseline.

Conclusion

Patients presented an increased oxidative damage and also a higher activation of pro-inflammatory pathways than healthy controls at baseline. After 6 months their level of oxidative stress continue increased. Pro-inflammatory parameters decreased overtime (MCP-1 and TNF α) but PGE2, increased surprisingly. This can be due to the fact that antipsychotics are not able to completely reverse baseline inflammation.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Cannabis and bipolar disorder: does quitting cannabis use during manic/mixed episode improve clinical/functional outcomes?

OBJECTIVE

To examine whether bipolar disorder patients who stop cannabis use during a manic/mixed episode have better clinical and functional outcomes than continued use or never use.

METHOD

Data from the European Mania in Bipolar Longitudinal Evaluation of Medication (EMBLEM), a 2-year prospective observational study in adults with a manic/mixed episode of bipolar disorder, was used. Three cannabis use groups were: current use (between 12-week and 24-month visits); no current but previous use (during first 12 weeks); and never use. Associations between cannabis use and outcomes were analyzed using regression models.

RESULTS

Of 1922 patients analyzed, 6.9% were current users, 4.6% previous users, and 88.5% never users. Clinical outcomes differed between groups (P<0.019): previous users had highest rates of remission (68.1%) and recovery (38.7%), and lowest rates of recurrence (42.1%) and relapse (29.8%). Logistic regression showed previous users had similar outcomes to never users (all P>0.05), whereas current users had lower recovery (P=0.004) and remission (P=0.014), higher recurrence (P=0.014), greater work impairment (P=0.016), and were more likely not to be living with partner (P=0.006) than never users.

CONCLUSION

Bipolar patients who stop using cannabis during manic/mixed episode have similar clinical and functional outcomes to never users, while continued use is associated with higher risk of recurrence and poorer functioning.

Detection of extended-spectrum beta-lactamase-producing Escherichia coli isolates in faecal samples of Iberian lynx

AIMS

To characterize the diversity of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli isolates recovered within the faecal microbiota of Iberian lynx. The identification of other associated resistance genes and the analysis of clonal relationship were also focused in this study.

METHODS AND RESULTS

From 2008 to 2010, 128 faecal samples of Iberian lynx (wild and captive animals) were collected. Eleven tested samples contained cefotaxime-resistant E. coli isolates (all belonging to captive animals) and 10 ESBL-producing isolates were showed. CTX-M-14 and SHV-12 ESBL-types were detected and seven different patterns were identified by pulsed-field gel electrophoresis analysis.

CONCLUSIONS

The occurrence of unrelated multiresistant E. coli in faecal flora of captive specimens of Iberian lynx, including the presence of ESBLs, resistant genes in integrons and virulence determinants was showed in this study.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results obtained in this study highlight the environmental problem as future reintroductions of Iberian lynx could lead to a spread of resistant bacteria. Additionally, ESBL-producing bacteria can represent a health problem for this endangered species.

Oxidative stress, inflammation and cognitive impairment in first psychotic patients

Introduction

Both oxidative stress and the inflammatory chemokine MCP-1 have been linked to the pathophysiology of certain mental illnesses such as psychosis. There are previous studies in rats and dogs suggesting that oxidative stress can cause cognitive impairment.

Objectives

To correlate oxidative stress and the chemokine MCP-1 levels with cognitive impairment in first episode psychosis.

Methods

28 patients with first episode psychosis and 28 healthy controls matched by sex and age were included in the study, who were given a battery of neurocognitive tests and we determined their blood levels of lipid peroxidation (TBARS), nitric oxide, total antioxidant status (TAS), glutathione, activity of enzymes catalase (CAT), glutathione peroxidase (cGPx) and superoxide dismutase (SOD) and the inflammatory chemokine MCP-1.

Results

Healthy controls had better TAS than patients and increased activity of enzymes cGPx and CAT.

We found a statistically significant negative relationship between levels of MCP-1 and working memory, attention and verbal memory. At higher levels of chemokines, worse cognitive functioning in these areas.

Verbal memory was also negatively related, in a meaningful way, with nitric oxide levels in blood.

Likewise, we found that higher levels of glutathione correlated with better scores on the 3 tests performed of verbal fluency.

Conclusions

In patients with a PEP, levels of certain markers of oxidative stress and inflammation are associated with poorer cognitive functioning.

Factors affecting seroprevalence of Toxoplasma gondii in the endangered Iberian lynx (Lynx pardinus)

Wild felids are considered important in maintaining the sylvatic cycle of Toxoplasma gondii. Although, T. gondii antibodies have been reported in several species of wild felids, little is known of the epidemiology and risk factors associated with T. gondii infection in wild cats. The Iberian lynx (Lynx pardinus) is the most endangered felid species in the world. In the present study, seroprevalence and associated risk factors for T. gondii infection in a large population of Iberian lynx in Spain were determined. Serum samples from 129 Iberian lynx collected from 2005 to 2009 and 85 wild rabbits (Oryctolagus cuniculus), sharing the habitat with the Iberian lynx, were tested for antibodies to T. gondii by the modified agglutination test (MAT) using a cut-off value of 1:25. Antibodies to T. gondii were found in 81 of 129 (62.8%) Iberian lynx. Seroprevalence to T. gondii in Iberian lynx significantly increased with age (P<0.001). T. gondii seroprevalences were similar in free-ranging (66.7% of 93) and wild-caught captive lynx (69% of 84) but significantly lower in captive-born lynx (22.5% of 40). Seroprevalence was higher in lynx with concurrent Cytauxzoonfelis (88% of 25) but not with concurrent Feline Leukemia Virus (FeLV) infection (53.8% of 13). There were no significant differences in seroprevalence between sexes, geographic region and year of sample collection (2005-2009). Oocysts of T. gondii were not detected microscopically in fecal samples from 58 lynx. Wild rabbits are considered the most important food for the lynx. Antibodies to T. gondii were found in 14 (11.9%) of 85 rabbits tested. The present results indicate that T. gondii infection is widespread in the two areas where Iberian lynx survive in Spain. The fact that four captive-born lynx seroconverted was indication of contact with T. gondii also in the Captive Breeding Centers, hence, control measures to prevent T. gondii infection would be necessary in these centers.

PK and PK/PD of doxycycline in drinking water after therapeutic use in pigs

A commercial doxycycline formulation was administered in drinking water to 12 pigs at the recommended dose of 10 mg/kg daily for 5 days. The mean plasma concentration at steady-state was 1.37 +/- 1.21 microg/mL, which was reached at 68 +/- 27.2 h postadministration. Absorption and elimination half-life values were 7.20 +/- 2.42 and 7.01 +/- 2.10 h, respectively. Most plasma concentrations during dosing were higher than the minimum inhibitory concentrations (MICs) described for the main porcine bacterial pathogens of the respiratory tract (Pasteurella multocida, Actinobacillus pleuropneumoniae, Bordetella bronchiseptica and Mycoplasma hyopneumoniae). It is concluded that when pigs were treated with doxycycline in drinking water at the recommended rate, therapeutically effective concentrations were achieved throughout the treatment period, supporting the clinical use of this tetracycline in the control of respiratory infections. However, inter-animal differences were marked.

Intraspecific characterization of Vibrio alginolyticus isolates recovered from cultured fish in Spain

AIMS

Intraspecific differentiation and characterization of Vibrio alginolyticus strains isolated from cultured fish in Spain.

MATERIALS AND RESULTS

Thirty-four Vibrio alginolyticus strains isolated from cultured fish were intraspecifically characterized on the basis of biochemical and exoenzymatic patterns, outer membrane protein (OMP) profiles, ribotyping and plasmid analyses. The typing methods used did not allow to group V. alginolyticus isolates on the basis of their sources of collection. A higher homogeneity was observed in OMP profiles. A high percentage of isolates were plasmidless. Ribotyping was the highest discriminatory typing method, as all the isolates tested presented 23 profiles using the HindIII restriction enzyme. On the basis of the ribotyping pattern, a similarity matrix and a dendrogram were constructed.

CONCLUSIONS

The results obtained indicate that V. alginolyticus strains isolated from southwestern Spain belong to different clonal lineages.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study has shown differences with other similar studies carried out in other areas of Europe with strains of V. alginolyticus with respect to the clonal lineages of the strains isolated in southwestern Spain.

Vibrio species isolated from diseased farmed sole, Solea senegalensis (Kaup), and evaluation of the potential virulence role of their extracellular products

Bacteria isolated from an outbreak with moderate mortalities in farmed sole, Solea senegalensis (Kaup), in the south of Spain were identified as Vibrio harveyi and V. parahaemolyticus. Only bacterial strains showing swarming were virulent in sole and caused mortalities in experimentally inoculated fish. However, the signs of the disease were only reproduced with V. harveyi. The intramuscular inoculation of the extracellular products (ECPs) of both species produced mortalities in inoculated fish and the appearance of surface ulcers in the case of V. harveyi. However, the inoculation of sublethal doses of ECPs to fish showed a protective effect against V. harveyi.

Adaptation of an [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay to evaluate the cytotoxicity of the extracellular products of micro-organisms pathogenic to fish

AIMS

Adaptation of a colorimetric assay using [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT) to evaluate the cytotoxicity of the extracellular products of micro-organisms pathogenic to fish.

METHODS AND RESULTS

The optimal conditions for the colorimetric assay were determined and this method was compared with the trypan blue exclusion assay. The protein concentration of extracellular products causing the death of 50% of the cell population (CI50) was determined.

CONCLUSIONS

This assay enables quantitative and objective comparison of the cytotoxicity of the extracellular products of micro-organisms pathogenic to fish. It was shown to be more accurate than conventional counting with the trypan blue exclusion assay.

SIGNIFICANCE AND IMPACT OF THE STUDY

This method may also be useful for characterizing the cytotoxicity of specific components of extracellular products.

Pathogenicity of Vibrio alginolyticus for cultured gilt-head sea bream (Sparus aurata L.)

The in vivo and in vitro pathogenic activities of whole cells and extracellular products of Vibrio alginolyticus for cultured gilt-head sea bream were evaluated. The 50% lethal doses ranged from 5.4 x 10(4) to 1.0 x 10(6) CFU/g of body weight. The strains examined had the ability to adhere to skin, gill, and intestinal mucus of sea bream and to cultured cells of a chinook salmon embryo cell line. In addition, the in vitro ability of V. alginolyticus to adhere to mucus and skin cells of sea bream was demonstrated by scanning electron microscopy. The biological activities of extracellular products of V. alginolyticus were hydrolytic activities; the products were able to degrade sea bream mucus. V. alginolyticus was cytotoxic for fish cell lines and lethal for sea bream. Moreover, the extracellular products could degrade sea bream tissues. However, experiments performed with the bath immersion inoculation technique demonstrated that V. alginolyticus should be considered a pathogen for sea bream only when the mucus layer is removed and the skin is damaged.

Kinetics of adhesion of selected fish-pathogenic Vibrio strains of skin mucus of gilt-head sea bream (Sparus aurata L.)

The kinetics of adhesion of Vibrio strains isolated from diseased fish to skin mucus of gilt-head sea bream was studied. A modified Langmuir adsorption isotherm was calculated, and the results obtained indicate that the strains tested (Vibrio alginolyticus DP1HE4 and Vibrio anguillarum-like DC12R8 and DC12R9) showed a saturation kinetics except for V. alginolyticus (CAN), which showed a proportional adsorption kinetics. The adhesive capability for skin mucus does not seem to be an essential virulence factor of pathogenic strains of Vibrio, since this specific interaction depended on several environmental factors, temperature and salinity being the most important. However, the absence of an inhibitory effect of mucus on the pathogenic microorganisms, and the capability of the Vibrio strains to utilize mucus as a carbon source, could favor their settlement on the skin with a potential for infection of cultured, stressed fish.