A bacterial ghost vaccine against Aeromonas salmonicida infection in turbot (Scophthalmus maximus).

Aeromonas salmonicida is one of the most prevalent pathogens that causes huge economic losses to aquaculture. Effective vaccination is the first choice for preventing infection. Bacterial ghost (BG), an empty bacterial shell devoid of cytoplasm, is a promising vaccine antigen with distinct advantages. Herein, we established strategies for producing a substantial yield of A. salmonicida ghost (ASG) and investigated the immune-protective properties of it. As a result, 2.84 mg/ml NaOH was discovered to be capable of inducing considerable amounts of ASG. Furthermore, the ASG vaccine elicited adaptive immunity in turbots after rapid activation of innate immunity. Even though formalin-killed cells (FKC) produced a few more antibodies than ASG, ASG ultimately provided a much stronger immune protection effect because it strengthened cellular immunity, with a relative percentage survival (RPS) of 50.1 % compared to FKC. These findings demonstrated that ASG effectively activated cell-mediated immunity, which helped get rid of microorganisms inside cells. Therefore, this study presented novel perspectives for future research on furunculosis vaccine products based on ASG as an antigen.

Inactivated Aeromonas salmonicida impairs adaptive immunity in lumpfish (Cyclopterus lumpus).

Aeromonas salmonicida, a widely distributed aquatic pathogen causing furunculosis in fish, exhibits varied virulence, posing challenges in infectious disease and immunity studies, notably in vaccine efficacy assessment. Lumpfish (Cyclopterus lumpus) has become a valuable model for marine pathogenesis studies. This study evaluated several antigen preparations against A. salmonicida J223, a hypervirulent strain of teleost fish, including lumpfish. The potential immune protective effect of A. salmonicida bacterins in the presence and absence of the A-layer and extracellular products was tested in lumpfish. Also, we evaluated the impact of A. salmonicida outer membrane proteins (OMPs) and iron-regulated outer membrane proteins (IROMPs) on lumpfish immunity. The immunized lumpfish were intraperitoneally (i.p.) challenged with 104 A. salmonicida cells/dose at 8 weeks-post immunization (wpi). Immunized and non-immunized fish died within 2 weeks post-challenge. Our analyses showed that immunization with A. salmonicida J223 bacterins and antigen preparations did not increase IgM titres. In addition, adaptive immunity biomarker genes (e.g., igm, mhc-ii and cd4) were down-regulated. These findings suggest that A. salmonicida J223 antigen preparations hinder lumpfish immunity. Notably, many fish vaccines are bacterin-based, often lacking efficacy evaluation. This study offers crucial insights for finfish vaccine approval and regulations.

A Bioactive Extract Rich in Triterpenic Acid and Polyphenols from Olea europaea Promotes Systemic Immunity and Protects Atlantic Salmon Smolts Against Furunculosis.

In the present study, the modulation of the transcriptional immune response (microarray analysis) in the head kidney (HK) of the anadromous fish Atlantic salmon (Salmo salar) fed a diet supplemented with an olive fruit extract (AQUOLIVE®) was evaluated. At the end of the trial (133 days), in order to investigate the immunomodulatory properties of the phytogenic tested against a bacterial infection, an in vivo challenge with Aeromonas salmonicida was performed. A total number of 1,027 differentially expressed genes (DEGs) (805 up- and 222 downregulated) were found when comparing the transcriptomic profiling of the HK from fish fed the control and AQUOLIVE® diets. The HK transcripteractome revealed an expression profile that mainly favored biological processes related to immunity. Particularly, the signaling of i-kappa B kinase/NF-kappa and the activation of leukocytes, such as granulocytes and neutrophils degranulation, were suggested to be the primary actors of the innate immune response promoted by the tested functional feed additive in the HK. Moreover, the bacterial challenge with A. salmonicida that lasted 12 days showed that the cumulative survival was higher in fish fed the AQUOLIVE® diet (96.9 ± 6.4%) than the control group (60.7 ± 13.5%). These results indicate that the dietary supplementation of AQUOLIVE® at the level of 0.15% enhanced the systemic immune response and reduced the A. salmonicida cumulative mortality in Atlantic salmon smolts.

GAS1: A New ß-Glucan Immunostimulant Candidate to Increase Rainbow Trout (Oncorhynchus mykiss) Resistance to Bacterial Infections With Aeromonas salmonicida achromogenes.

ß-glucans are prebiotic and/or food additives used by the aquaculture industry to enhance the immune response of fish. Their efficiency may vary according to their origin and structure. In this study, the immunostimulant effects of two ß-glucan types extracted from wild-type baker's yeast (Saccharomyces cerevisiae) and its null-mutant Gas1 were investigated. Gas1 has a beta-1,3-glucanosyltransferase activity necessary for cell wall assembly. Using a positive (commercial product MacroGard®) and a negative control (a diet without glucans), we evaluated the immune responses and disease resistance of rainbow trout juveniles (mean weight, ~44 g) fed control, low (0.2%) and high (0.5%) doses of Macrogard®, Gas1, and Wild type-ß-glucan after a short-term (15 days, D15) or mid-term (36 days, D36) feeding periods. We found that ß-glucan supplemented diets did not affect growth performance, mortality, splenic index, or leukocyte respiratory burst activity on D15 nor D36. However, each ß-glucan triggered different immune effectors, depending of the doses or length of exposure compared to others and/or the negative control. Indeed, high dose of MacroGard® significantly increased lysozyme activities at D15 compared with the control and other diets (p<0.05). At D36, MacroGard ß-glucan enhanced the production of lymphocytes in comparison with the control diet (p<0.05). Regarding WT ß-glucan, at D36, WT-ß-glucan, especially the high dose, provided the highest enzymatic activities (lysozyme and ACH50) and Ig level (p<0.01). Furthermore, on D36, Gas1 also increased lysozyme activity, Ig proportion, and some immune genes (mcsfra, hepcidin) compared with MacroGard® (p<0.05). Besides, both doses of Gas1-ß-glucans increased the resistance of juveniles to bacterial infection highlighted by a higher survival rate at 14 days post-challenge compared with the control and other types and doses of ß-glucans (p<0.05). In conclusion, our results suggest that Gas1-ß-glucan could represent a promising immunostimulant that would help to prevent diseases in aquaculture even more efficiently than other ß-glucans already in use. Mode of action and particular efficiency of this new Gas1 mutant are debated.

Characterization of Aeromonas salmonicida and A. sobria isolated from cultured salmonid fish in Korea and development of a vaccine against furunculosis.

Previously, Aeromonas sobria and A. salmonicida were identified to be the most prevalent species in salmonid farms in Korea. In this study, we evaluated the biochemical characteristics, antibiotic susceptibility and pathogenicity of A. salmonicida (3 isolates) and A. sobria (8 isolates) isolated from salmonids, and further investigated efficacy of A. salmonicida vaccine. In antibiotic susceptibility test, all of A. sobria isolates were resistant to amoxicillin and ampicillin. Six A. sobria and two A. salmonicida isolates were resistant to oxytetracycline. In challenge test, A. sobria isolates exhibited low pathogenicity in rainbow trout (Oncorhynchus mykiss) while one A. salmonicida isolate showed high pathogenicity with LD50 of 6.4 × 103  CFU/fish in rainbow trout and coho salmon (Oncorhynchus kisutch). Among virulence factors, secretion apparatus (ascV and ascC) and transcription regulatory protein (exsA) of type 3 secretion system and A-layer protein genes were differentially detected in DNA or cDNA of A. salmonicida isolates, indicating their contribution to the pathogenicity. A formalin-killed vaccine of highly pathogenic A. salmonicida isolate exhibited a protective effect with relative survival rate of 81.8% and 82.9% at 8 weeks and 16 weeks post-vaccination, respectively, in challenge test.

A pentavalent vaccine for rainbow trout in Danish aquaculture.

Mariculture in Denmark is based on production of rainbow trout grown two years in fresh water followed by one growth season in sea cages. Although the majority of rainbow trout are vaccinated against the most serious bacterial pathogens - Aeromonas salmonicida subsp. salmonicida, Vibrio anguillarum and Yersinia ruckeri, by the use of commercially available vaccines, disease outbreaks requiring treatment with antibiotics still occur. The present study tested the potential of a new experimental multicomponent vaccine that is based on local bacterial strains, isolated from rainbow trout in Danish waters, and thus custom-designed for Danish rainbow trout mariculture. The vaccination with the multicomponent vaccine resulted in protection against three relevant bacterial diseases (yersiniosis, furunculosis, vibriosis) under experimental conditions. We showed that i.p. injection of the vaccine induced specific antibody responses in trout against the different bacterial antigens and regulated expression of genes encoding SAA, C3, IL-1ß, IL-6, IL-8, IgD and MHCII.

Vaccine-Induced Protection Against Furunculosis Involves Pre-emptive Priming of Humoral Immunity in Arctic Charr.

With respect to salmonid aquaculture, one of the most important bacterial pathogens due to high mortality and antibiotic usage is the causative agent of typical furunculosis, Aeromonas salmonicida spp. salmonicida (Asal). In Atlantic salmon, Salmo salar, the host response during infections with Asal is well-documented, with furunculosis outbreaks resulting in significant mortality in commercial settings. However, less is known about the host-pathogen interactions in the emerging aquaculture species, Arctic charr Salvelinus alpinus. Furthermore, there is no data on the efficacy or response of this species after vaccination with commonly administered vaccines against furunculosis. To this end, we examined the immunological response of S. alpinus during infection with Asal, with or without administration of vaccines (Forte Micro®, Forte Micro® + Renogen®, Elanco Animal Health). Artic charr (vaccinated or unvaccinated) were i.p.-injected with a virulent strain of Asal (106 CFUs/mL) and tissues were collected pre-infection/post-vaccination, 8, and 29 days post-infection. Unvaccinated Arctic charr were susceptible to Asal with 72% mortalities observed after 31 days. However, there was 72-82% protection in fish vaccinated with either the single or dual-vaccine, respectively. Protection in vaccinated fish was concordant with significantly higher serum IgM concentrations, and following RNA sequencing and transcriptome assembly, differential expression analysis revealed several patterns and pathways associated with the improved survival of vaccinated fish. Most striking was the dramatically higher basal expression of complement/coagulation factors, acute phase-proteins, and iron hemostasis proteins in pre-challenged, vaccinated fish. Remarkably, following Asal infection, this response was abrogated and instead the transcriptome was characterized by a lack of immune-stimulation compared to that of unvaccinated fish. Furthermore, where pathways of actin assembly and FcγR-mediated phagocytosis were significantly differentially regulated in unvaccinated fish, vaccinated fish showed either the opposite regulation (ForteMicro®), or no impact at all (ForteMicro®Renogen®). The present data indicates that vaccine-induced protection against Asal relies on the pre-activation and immediate control of humoral immune parameters that is coincident with reduced activation of apoptotic (e.g., NF-κB) and actin-associated pathways.

Four selenoprotein P genes exist in salmonids: Analysis of their origin and expression following Se supplementation and bacterial infection.

The following research was conducted to elucidate the evolution and expression of salmonid selenoprotein P (SelP), a selenoprotein that is unique in having multiple selenocysteine (Sec) residues, following supranutritional selenium supplementation and infection in rainbow trout. We show that in salmonids SelP is present as four paralogues and that the diversification of SelP genes during vertebrate evolution relates to whole genome duplication events. With 17 and 16 selenocysteine residues for rainbow trout (Oncorhynchus mykiss)/Atlantic salmon (Salmo salar) SelPa1 and SelPa2 proteins respectively and 1 or 2 (trout or salmon) and 4 or 3 (trout or salmon) selenocysteine residues for salmonid SelPb1 and SelPb2 proteins respectively, this is the highest number of (predicted) multiple selenocysteine containing SelP proteins reported for any vertebrate species to date. To investigate the effects of selenium form on SelP expression we added different concentrations (1 nM- 10 µM) of organic or inorganic selenium to a trout cell line (RTG-2 cells) and analysed changes in mRNA abundance. We next studied the impact of supplementation on the potential modulation of these transcripts by PAMPs and proinflammatory cytokines in RTG-2 and RTS-11 cells. These experiments revealed that selenium type influenced the responses, and that SelP gene subfunctionalisation was apparent. To get an insight into the expression patterns in vivo we conducted a feeding trial with 2 diets differing in selenium content and 5 weeks later challenged the trout with a bacterial pathogen (Aeromonas salmonicida). Four tissues were analysed for SelP paralogue expression. The results show a significant induction of SelPa1 in gills and intestine following infection in selenium supplemented fish and for SelPa2 in gills. SelPb1 was significantly reduced in head kidney of both diet groups following infection, whilst SelPb2 was significantly upregulated in skin of both diet groups post infection. Overall these findings reveal differential expression profiles for the SelPa/SelPb paralogues in trout, influenced by selenium supply, cell type/tissue and stimulant. The increase of multiple Sec containing SelP proteins in salmonids could indicate an enhanced requirement for selenium in this lineage.

Analysis of adipose tissue immune gene expression after vaccination of rainbow trout with adjuvanted bacterins reveals an association with side effects.

Most existing fish vaccines are presented in the form of oil-based emulsions delivered by intraperitoneal injection. Whilst very effective they are frequently associated with inflammatory responses that can result in clinically significant side-effects often involving the adipose tissue that is in direct contact with the vaccine. To explore the potential of immune gene expression changes in the adipose tissue of fish to be markers of vaccination efficacy or development of side-effects we have studied the response to a bacterial (Aeromonas salmonicida) vaccine administered with two different adjuvants. The first adjuvant was Montanide™ ISA 763A VG, thought to induce a mostly humoral response, and the second was Montanide™ ISA 761 VG that gives a more balanced humoral and cell mediated response. Following vaccination tissue samples were collected at days 3, 14 and 28 for RTqPCR analysis. Fifty immune genes were studied with a focus on a) pro-inflammatory associated molecules and b) adaptive immune response related molecules linked with possible Th1, Th2, Th17 and T-regulatory pathways, with the expression data analysed for associations with Speilberg post-vaccination side effect scores. The results showed that the adipose tissue is a particularly sensitive and discriminatory tissue for studying adjuvant effects. A clear upregulation of many immune genes occurred in response to both vaccine groups, which persisted over time and overlapped with the appearance of visible adhesions. Our analysis revealed a relationship between adipose tissue immune function and the development of vaccine-induced adhesions giving the potential to use immune gene expression profiling in this tissue to predict the side-effects seen.

Pharmacokinetic model of florfenicol in turbot (Scophthalmus maximus): establishment of optimal dosage and administration in medicated feed.

The pharmacokinetics of florfenicol (FF) in turbot (Scophthalmus maximus) was studied after single intravenous (10 mg kg-1 ) and oral (100 mg kg-1 ) administration. The plasma concentration-time data of florfenicol were described by an open one-compartment model. The elimination half-life (t1/2 ) was estimated to be 21.0 h, and the total body clearance, Cl, was determined as 0.028 L kg h-1 . The apparent volume distribution (Vd ) was calculated to be 0.86 L kg-1 and the mean residence time (MRTiv ) was 30.2 h. Following oral administration, the maximum plasma concentration (Cmax ) of 55.4 µg mL-1 was reached at 12 h (Tmax ). The absorption constant (ka ) was 0.158 h-1 . The bioavailability was estimated to be 57.1%. The low bioavailability observed at higher doses was explained by the saturation of the mechanisms of absorption. The drug absorption process was limited by its inherent low solubility, which limited the amount of available FF absorbed in the gastrointestinal tract. Based on the pharmacokinetic data, an optimal dosing schedule for FF administration is hereby provided. Based on the minimum inhibitory concentration found for susceptible strains of Aeromonas salmonicida, oral FF administration of first, an initial dose of 30 mg FF kg-1 , followed by 6 maintenance doses at 18 mg kg-1 /daily could be effective against furunculosis in turbot.

The effects of increasing dietary levels of soy protein concentrate (SPC) on the immune responses and disease resistance (furunculosis) of vaccinated and non-vaccinated Atlantic salmon (Salmo salar L.) parr.

Juvenile salmon, with an initial weight of 9 g, were fed three experimental diets, formulated to replace 35 (SPC35), 58 (SPC58) and 80 (SPC80) of high quality fishmeal (FM) with soy protein concentrate (SPC) in quadruplicate tanks. Higher dietary SPC inclusion was combined with increased supplementation of methionine, lysine, threonine and phosphorus. The experiment was carried out for 177 days. On day 92 salmon in each tank were bulk weighed. Post weighing eighty salmon from each tank were redistributed in two sets of 12 tanks. Salmon from the first set of tanks were vaccinated, while the second group was injected with phosphate buffer saline (PBS). Salmon were sampled on day 92 (pre-vaccination), day 94 (2 days post vaccination [dpv]/PBS injection [dpPBSinj]) and day 154 (62 dpv/dpPBSinj) of the trial for the assessment of their immune responses, prior to the performance of salmon bulk weights for each tank. On day 154, fish from each tank were again bulk weighed and then seventeen salmon per tank were redistributed in two sets of twelve tanks and intra-peritoneally infected with Aeromonas salmonicida. At Day 154, SPC80 demonstrated lower performance (weight gain, specific growth rate and thermal growth coefficient and feed conversion ratio) compared to SPC35 salmon. Reduced classical and total complement activities for salmon fed diets with over 58% of protein from SPC, were demonstrated prior to vaccination. Reduced alternative complement activity was detected for both SPC58 and SPC80 salmon at 2 dpv and for the SPC80 group at 62 dpv. Total and classical complement activities demonstrated no differences among the dietary groups after vaccination. Numerical increases in classical complement activity were apparent upon increased dietary SPC levels. Increased phagocytic activity (% phagocytosis and phagocytic index) was exhibited for the SPC58 group compared to SPC35 salmon at 62 dpPBSinj. No differences in serum lysozyme activity, total IgM, specific antibodies, protein, glucose and HKM respiratory burst were detected among the dietary groups at any timepoint or state. Mortalities as a result of the experimental infection only occurred in PBS-injected fish. No differences in mortality levels were demonstrated among the dietary groups. SPC58 diet supported both good growth and health in juvenile Atlantic salmon while SPC80 diet did not compromise salmon' immunity or resistance to intraperitoneally inflicted furunculosis.

A comparison of the response of diploid and triploid Atlantic salmon (Salmo salar) siblings to a commercial furunculosis vaccine and subsequent experimental infection with Aeromonas salmonicida.

Sterile triploid fish represent a solution to the problems associated with sexual maturation and escapees in aquaculture. However, as disease outbreaks continue to cause significant economic losses to the industry, it is essential that the response of triploids to disease and disease treatments be characterised. The aim of this study was to compare the response of triploid Atlantic salmon to a commercial furunculosis vaccine with that of diploid fish, and to assess the vaccine efficacy in the two ploidies through an experimental infection with Aeromonas salmonicida. Diploid and triploid Atlantic salmon were injected intraperitoneally with either phosphate buffered saline, liquid paraffin adjuvant or a commercial furunculosis vaccine. Following vaccination, growth, adhesion scores and a variety of assays to assess immune function, such as respiratory burst and antibody response, were measured. Vaccination did not have a significant effect on the weight of either ploidy prior to challenge at 750° days. Adhesion scores were significantly higher in vaccinated fish compared to unvaccinated fish, although no effect of ploidy was observed. Ploidy significantly affected respiratory burst activity following vaccination, however, with triploids exhibiting higher activity than diploids. Combined with lower white blood cell numbers observed in the triploids, it may be that this low cell number is compensated for by increased cellular activity. Ploidy however, did not have a significant effect on complement activity or antibody response, with significantly higher antibody levels detected in all vaccinated fish compared to unvaccinated controls. In addition, both ploidy groups were well protected following challenge with no difference in the relative percentage survival. Based on these results, it appears that ploidy does not affect the severity of adhesions that result post-vaccinate or in the fish's immune response following vaccination, and the furunculosis vaccine performs equally well in both diploid and triploid Atlantic salmon.

Aeromonas salmonicida infection levels in pre- and post-stocked cleaner fish assessed by culture and an amended qPCR assay.

Due to increasing resistance to chemical therapeutants, the use of 'cleaner fish' (primarily wrasse, Labridae, species) has become popular in European salmon farming for biocontrol of the salmon louse, Lepeophtheirus salmonis (Krøyer). While being efficient de-licers, cleaner fish mortality levels in salmon cages are commonly high, and systemic bacterial infections constitute a major problem. Atypical furunculosis, caused by Aeromonas salmonicida A-layer types V and VI, is among the most common diagnoses reached in clinical investigations. A previously described real-time PCR (qPCR), targeting the A. salmonicida A-layer gene (vapA), was modified and validated for specific and sensitive detection of all presently recognized A-layer types of this bacterium. Before stocking and during episodes of increased mortality in salmon cages, cleaner fish (primarily wild-caught wrasse) were sampled and screened for A. salmonicida by qPCR and culture. Culture indicated that systemic bacterial infections are mainly contracted after salmon farm stocking, and qPCR revealed A. salmonicida prevalences of approximately 4% and 68% in pre- and post-stocked cleaner fish, respectively. This underpins A. salmonicida's relevance as a contributing factor to cleaner fish mortality and emphasizes the need for implementation of preventive measures (e.g. vaccination) if current levels of cleaner fish use are to be continued or expanded.

Incidence and recurrence of boils and abscesses within the first year: a cohort study in UK primary care.

BACKGROUND: Boils and abscesses are common in primary care but the burden of recurrent infection is unknown. AIM: To investigate the incidence of and risk factors for recurrence of boil or abscess for individuals consulting primary care. DESIGN AND SETTING: Cohort study using electronic health records from primary care in the UK. METHOD: The Health Improvement Network (THIN) database was used to identify patients who had consulted their GP for a boil or abscess. Poisson regression was used to examine the relationship between age, sex, social deprivation, and consultation and to calculate the incidence of, and risk factors for, repeat consultation for a boil or abscess. RESULTS: Overall, 164 461 individuals were identified who consulted their GP for a boil or abscess between 1995 and 2010. The incidence of first consultation for a boil or abscess was 512 (95% CI = 509 to 515) per 100 000 person-years in females and 387 (95% CI = 385 to 390) per 100 000 person-years in males. First consultations were most frequent in younger age groups (16-34 years) and those with the greatest levels of social deprivation. The rate of repeat consultation for a new infection during follow up was 107.5 (95% confidence interval [CI] = 105.6 to 109.4) per 1000 person-years. Obesity (relative risk [RR] 1.3, 95% CI = 1.2 to 1.3), diabetes (RR 1.3, 95% CI = 1.2 to 1.3), smoking (RR 1.3, 95% CI = 1.2 to 1.4), age <30 years (RR 1.2, 95% CI = 1.2 to 1.3), and prior antibiotic use (RR 1.4, 95% CI = 1.3-1.4) were all associated with repeat consultation for a boil or abscess. CONCLUSION: Ten percent of patients with a boil or abscess develop a repeat boil or abscess within 12 months. Obesity, diabetes, young age, smoking, and prescription of an antibiotic in the 6 months before initial presentation were independently associated with recurrent infection, and may represent options for prevention.

The adjuvant effect of low frequency ultrasound when applied with an inactivated Aeromonas salmonicida vaccine to rainbow trout (Oncorhynchus mykiss).

Vaccine adjuvants are classified according to their properties of either inducing the persistence of antigens within the animal after immunisation and/or activation of the animal's immune response. The adjuvant effect of low intensity low frequency sonophoresis (LFS) was tested in rainbow trout using an Aeromonas salmonicida bacterin vaccine administered by immersion vaccination using LFS at 37 kHz. The adjuvant effect obtained with LFS was compared with that of normal immersion or intraperitoneal injection vaccination. Quantitative PCR was used to measure bacterial DNA in vaccinated fish up to 35 days post-vaccination, while RT-qPCR was used to assess gene expression during the early and late immune response post-vaccination. Results showed that antigen uptake in the gills was significantly higher in the group exposed to low intensity LFS compared to the other two vaccination groups 15 min post-vaccination, but this initially high uptake did not persist over the rest of the experiment. In the kidney, by comparison, the vast majority of the samples analysed did not show the presence or persistence of the bacterin. Showing that the route of vaccine uptake using the A. salmonicida bacterin, does not influence the persistence of the bacterin in the gills or the kidney. On the other hand, LFS induced a higher inflammatory response and T-helper cell activation, characterized by a significant up-regulation of interleukin-8 (IL-8), IL-1ß and CD-4, respectively. The expression of Ig-M, Ig-T and Ig-D was up-regulated in gills (being significant for Ig-M), but not in the spleen and kidney of the sonicated group. Conversely, Ig-M was up-regulated in the spleen of the non-sonicated groups, but not in the sonicated group. This highlights the ability of ultrasound to enhance mucosal immunity. It remains to be established whether the up-regulation of Ig-M in gills would be sufficient to offer protection in fish infected with A. salmonicida.

Tissue-specific responses of oxidative stress biomarkers and antioxidant defenses in rainbow trout Oncorhynchus mykiss during a vaccination against furunculosis.

The present study was conducted to evaluate the effects of vaccination against furunculosis on responses of oxidative stress and antioxidant defenses in rainbow trout Oncorhynchus mykiss muscle, gills, liver, and brain tissues. The oxidative stress markers (malondialdehyde and carbonyl derivatives of protein oxidative destruction levels), antioxidant defenses (superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase), and total antioxidant capacity in different tissues of rainbow trout were measured. Our data showed that exposure of trout to vaccine against furunculosis produced changes (either increase or decrease) in oxidative stress and antioxidant enzymes responses, and these responses showed marked organ differences, associated with tissue patterns. Our study demonstrated that vaccinated trout showed alteration in antioxidant defenses and oxidative stress responses, with higher severity in the liver, compared with other tissues. Our data also suggest that vaccination against furunculosis induced lipid peroxidation in gill and liver tissues. However, muscle and brain tissue are capable of restoring its pro- and antioxidant balance after vaccination.

Long-lasting protection induced by bath vaccination against Aeromonas salmonicida subsp. salmonicida in rainbow trout.

For decades Aeromonas salmonicida subsp. salmonicida (from here referred to as A. salmonicida) has been recognized as the causative agent of typical furunculosis. This disease has had a major impact on aquaculture worldwide, making it a target for international research, particularly within the field of immunoprohylaxis. Initial studies attempted vaccination via oral route and immersion. However, these vaccination methods proved insufficient when compared to intraperitoneally (i.p.) injected vaccines. The focus of vaccine research regarding A. salmonicida shifted towards the i.p.-injected vaccines during the 1980's and -90's, resulting in oil-adjuvanted vaccines providing high levels of protection over longer periods of time. The majority of this research has been conducted using salmon, while rainbow trout, which is also a commercially important species, has played a much less central role. In this study, we have examined the effect of a bath vaccination using an experimental A. salmonicida bacterin. Rainbow trout were vaccinated by a 5 min bath in a formalin-inactivated bacterin. Half of these fish was booster vaccinated using 50% of the initial vaccine dose 10 weeks post primary immunization. Along with an un-vaccinated control group, the fish were challenged by waterborne infection 24 weeks post primary immunization. Both vaccinated groups showed a significantly increased survival (>93% survival) compared to a 70% survival in the un-vaccinated control group (P = 0.005 and P = 0.019 for single and dual immunizations, respectively). When comparing the survival of the single and dual immunization groups, there was no significant difference (P = 0.531). ELISA showed no significant induction of specific circulating antibodies in either vaccinated group. These results are interesting with regard to the protective mechanisms, seen in the light of previous results obtained using bath as well as i.p. vaccination against furunculosis in salmonid fishes.

Recurrent furunculosis: Efficacy of the CMC regimen--skin disinfection (chlorhexidine), local nasal antibiotic (mupirocin), and systemic antibiotic (clindamycin).

BACKGROUND: The treatment of recurrent furunculosis is poorly documented and represents a public health challenge. The medical care of this disease is often disappointing, especially as the disease evolution is uncertain and relapses occur. We report the efficacy and safety of our CMC regimen: skin disinfection (chlorhexidine), local nasal antibiotic (mupirocin), and systemic antibiotic (clindamycin). METHODS: Patients attending our institution during the period 2006-2012 for recurrent furunculosis (≥ 4 episodes/y) were enrolled in the study. Clinical and bacteriological data were collected. Staphylococcus aureus colonization was also investigated in close contacts, and carriers were treated. Patients were treated with the CMC regimen: skin disinfection with chlorhexidine for 21 days, nasal mupirocin ointment for 5 days, and oral clindamycin 1800-2400 mg for 21 days. RESULTS: Nineteen patients were included. Their mean age was 36 ± 14.5 y and the male to female sex ratio was 1.1. Screening swabs from all sites were S. aureus-positive in 63% (n = 12), including 4 methicillin-resistant S. aureus (MRSA). Before the CMC regimen, the median time to relapse was 31 days (mean 52 days). The mean number of recurrences was 5.5 ± 2.4/y. After the CMC regimen, among 16 patients who had a complete follow-up, 14 were healed beyond 9 months. Two recurrences occurred, 1 in an MRSA carrier and 1 in a patient with an insufficiently treated dermatosis. No serious side effect occurred that required the cessation of treatment. CONCLUSIONS: There are 2 major routes involved in recurrent furunculosis: risk factors and staphylococcal colonization of close contacts. Our procedure is safe and effective, with 87% remission beyond 9 months. It merits testing on larger numbers of participants.

Antibody responses correlate with antigen dose and in vivo protection for oil-adjuvanted, experimental furunculosis (Aeromonas salmonicida subsp. salmonicida) vaccines in Atlantic salmon (Salmo salar L.) and can be used for batch potency testing of vaccines.

Salmon farming has increased dramatically over last thirty years and a key to the success is the introduction of protective vaccines. In Norway, almost 100% of all Atlantic salmon are vaccinated prior to sea transfer. This extensive use of vaccines demands use of a lot of resources in production and quality control of vaccines, and fish are now one of the most widely used laboratory animal species in Norway, since all batch testing today is performed by challenge experiments. With an increasing focus on the 3 R's (Replacement, Reduction and Refinement), new methods are needed. The aim of this study was to assess the use of different vaccine evaluation methods to identify furunculosis vaccines of different "potency", using ELISA as in vitro assay and intraperitoneal and cohabitation challenge as in vivo assays. Eleven vaccines with different antigen content (0, 2, 5, 10, 20, 40, 80, 100 and 200%) and different antigen qualities were included in the study. Challenge and blood sampling for the ELISA assay were conducted 9 weeks post vaccination. The results from this study indicated that there is a close correlation between the antigen dose in the vaccine and the antibody response against Aeromonas salmonicida as measured by ELISA. There is also a close correlation between the antibody response and protection for both i.p. and cohabitation challenge models. The ELISA method identified sub-potent batches better than currently used in vivo assay (i.p challenge) and seems to be the best method of performing a batch potency test of furunculosis vaccines particularly when taking the 3R's principles into account.