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Structure and gene cluster annotation of the O-antigen of Aeromonas sobria strain K928 isolated from common carp and classified into the new Aeromonas PGO1 serogroup
Microbiological studies of the round goby ( Neogobius melanostomus) from the Puck Bay, southern Baltic Sea
Biomarkers of oxidative stress, biochemical changes, and the activity of lysosomal enzymes in the livers of rainbow trout (Oncorhynchus mykiss Walbaum) vaccinated against yersiniosis before a Yersinia ruckeri challenge
Abstract Introduction This study aimed to evaluate biomarkers of oxidative stress (2-thiobarbituric acid reactive substances, aldehyde and ketone derivatives of oxidatively modified proteins and total antioxidant capacity), the activity of antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase), that of lysosomal enzymes (alanyl aminopeptidase, leucyl aminopeptidase, β-N-acetylglucosaminidase and acid phosphatase) and changes in biochemical parameters (alanine aminotransferase, aspartate aminotransferase, de Ritis ratio, lactate dehydrogenase activity, lactate and pyruvate levels and their ratio) in the liver tissue of fish that were vaccinated against enteric redmouth disease and challenged with its causative agent, the bacterium Yersinia ruckeri. Material and Methods The vaccine was administered orally to trout, some of which were challenged with Y. ruckeri 61 days later. For comparison, unvaccinated and unchallenged trout and unvaccinated and challenged trout were also evaluated. Results In the unvaccinated fish, infection with Y. ruckeri disrupted the pro-oxidant/antioxidant balance, led to a significant increase in lipid peroxidation and oxidative modification of proteins, decreased total antioxidant capacity and significantly increased the activity of lysosomal enzymes. In vaccinated fish, the Y. ruckeri challenge increased the activity of glutathione-related enzymes and decreased lipid peroxidation, anaerobic metabolism and the activity of lysosomal enzymes in fish livers relative to the unvaccinated and challenged group. In contrast, these parameters increased after the Y. ruckeri challenge in unvaccinated trout relative to those in the untreated group. Conclusion Vaccination exerted a protective effect during the Y. ruckeri challenge and had no adverse effect on fish livers.
Is Shewanella oncorhynchi a fish health threat? Possible genetic background of pathogenicity and common carp challenge
Abstract Introduction The Shewanella genus is widely distributed in aquatic environments and occurs in different niches with a wide range of temperatures and salinities. It includes a novel species, S. oncorhynchi, described as recently as 2022, causing lens atrophy, inappetence and growth retardation in rainbow trout (Oncorhynchus mykiss, Walbaum 1792). Shewanella oncorhynchi also occurs in common carp (Cyprinus carpio L.), but its potential pathogenicity in this species is unclear. Material and Methods In this study, the pathogenicity of three well-characterised S. oncorhynchi strains was assessed in vivo in experimental infection of common carp and in vitro by estimation of their cytotoxicity to an epithelioma papulosum cyprini cell line. The strains’ characterisation involved whole-genome sequencing to identify possible virulence genes. Results Our study proved the pathogenicity of S. oncorhynchi to common carp and the bacterium’s cytotoxicity to epithelioma papulosum cyprini cells. Swollen abdomens, lens opacity, areas of discoloration and skin lesions were recorded in infected common carp. However, the ability to cause disease symptoms and mortality depended on the strain. Conclusion The study showed the potential roles of the quorum-sensing system, type IV pili, fimbriae, stress survival, iron metabolism and secretion system genes in the virulence of S. oncorhynchi. Of these, the vscC2, vscN2, vscR2, vscS2 and vscU2 type III secretion system genes potentially and probably enhance the bacterium’s ability to cause lesions in common carp.
Temporal modulation of oxidative stress and antioxidant capacity in rainbow trout (Oncorhynchus mykiss Walbaum) following Yersinia ruckeri vaccination
This study investigated the temporal effects of Yersinia ruckeri vaccination on markers of oxidative stress and antioxidant capacity in the livers of rainbow trout (Oncorhynchus mykiss Walbaum). Oxidative stress was assessed using 2-thiobarbituric acid-reactive substances (TBARS), oxidatively modified protein (OMP) derivatives and total antioxidant capacity (TAC) at three time points: baseline and one and two months post-vaccination. TBARS levels exhibited a transient peak one month after vaccination, suggesting a short-term increase in lipid peroxidation associated with immune activation. In contrast, TAC increased progressively over the experimental period, reaching significantly higher levels in vaccinated fish after two months, which is indicative of enhanced systemic antioxidant defences. OMP derivatives exhibited moderate variability: aldehydic forms peaked in the control group at one month, while ketonic forms were highest at baseline. However, no significant vaccination effect was observed. Correlation analysis revealed a strong negative association between TBARS and TAC (r = −0.58), supporting the role of antioxidant capacity in mitigating oxidative damage. Effect size and variability analyses confirmed substantial time- and treatment-related changes, particularly with regard to TBARS reduction and TAC enhancement in vaccinated fish. Overall, the results demonstrate a biphasic oxidative response to vaccination characterised by an initial oxidative challenge followed by adaptive antioxidant upregulation, highlighting the importance of modulation of redox balance in immune protection and aquaculture health management.
Time-dependent changes in oxidative stress biomarkers and activities of lysosomal and antioxidant enzymes in hepatic tissue of rainbow trout (Oncorhynchus mykiss Walbaum) following vaccination against Yersinia ruckeri
Abstract This study analyzed time-dependent effects of vaccination against Y. ruckeri on the oxidative mechanism underlying those effects by detecting relevant lipid peroxidation (2-thiobarbituric acid reactive substances, TBARS) and protein oxidation biomarkers [aldehydic and ketonic derivatives of oxidatively modified proteins (OMP)], antioxidant defenses [activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), total antioxidant capacity (TAC)], as well as activities of lysosomal functioning [alanyl aminopeptidase (AAP), leucyl aminopeptidase (LAP), acid phosphatase (AcP), and β-N-acetylglucosaminidase (NAG)] in hepatic tissue of rainbow trout, Oncorhynchus mykiss (Walbaum) following anti-Y. ruckeri vaccination in the first, second, and sixth months. A concentrated vaccine with Y. ruckeri strains was enclosed in fish feed and was administered three times every other day. Rainbow trout from each group were euthanized 31, 61, and 181 days following vaccination, and hepatic tissue was sampled for analysis. In the current study, vaccination against Y. ruckeri resulted in a no statistically significant change in TBARS levels, while aldehydic and ketonic derivatives of OMP in hepatic tissue decreased, especially after the first and second months following immunization. Moreover, the activities of glutathione-dependent enzymes increased, especially after the first and sixth months. The highest TAC levels were observed two and six months after vaccination. It has been shown that vaccination-related oxidative stress in hepatic tissue is involved in adaptive responses through the temporary mobilization of antioxidant and lysosomal enzymes in rainbow trout. The present study showed the effect of vaccination on lysosome membrane permeability for carbohydrate cleavage after the development of immunity against Yersinia, whereas antioxidant defence was reduced. Our results confirmed that the concept of preserving antioxidant enzyme function after vaccination was also evident when CAT, GR, and GPx activities either increased or were unchanged following vaccination.
Microbiological analysis of skin lesions of cod (Gadus morhua) from the southern part of the Baltic Sea
Abstract Introduction Since the middle of the 1980s, severe skin disorders have been observed in Baltic cod (Gadus morhua) each year. Available data on the spectrum of bacteria isolated from the clinical cases being limited, and evaluation of the microbial background of fish skin lesions being useful, a bacteriological examination has been undertaken. Material and Methods A total of 1,381 cod were caught during two voyages of the Baltica research vessel in the Polish exclusive economic zone of the southern Baltic Sea. After an examination which found lesions in 164 of the fish, a microbiological analysis was performed to isolate bacteria from them. The collected strains were phenotyped and genotyped, and their antimicrobial resistance was analysed by minimum inhibitory concentration (MIC) techniques. Results Bacteriological examinations provided 850 isolates. The dominant microorganisms were mesophilic Aeromonas spp., Pseudomonas spp. and Shewanella baltica. Opportunistic bacteria potentially hazardous to human health were also isolated, e.g. Alcaligenes faecalis, Staphylococcus epidermidis, Stenotrophomonas maltophilia and Vibrio sp. The MIC analysis determined the highest number of bacteria to resist sulphamethoxazole and amoxicillin and clavulanic acid. Conclusion Most of the collected bacteria were opportunistic pathogens for fish, widespread in the aquatic environment, and potentially threatening to humans.
Autophagic function of the liver of vaccinated rainbow trout (Oncorhynchus mykiss Walbaum) following Yersinia ruckeri infection
The liver plays a critical role in maintaining metabolic homeostasis and immune defence in fish, particularly in response to bacterial infections. Autophagy, a conserved cellular process essential for homeostasis and pathogen clearance, has been implicated in host defence mechanisms. However, the role of autophagy in the liver of vaccinated fish following pathogen exposure remains largely unexplored. Yersinia ruckeri, the causative agent of enteric redmouth disease (ERM), poses a significant threat to rainbow trout (Oncorhynchus mykiss Walbaum) aquaculture, primarily affecting the liver, spleen and kidneys. Vaccination is a widely used preventive strategy, but its effect on autophagic activity during infection is not well understood. The aim of this study was to evaluate the autophagic response in the liver of vaccinated rainbow trout following Y. ruckeri infection by assessing the activity of four lysosomal enzymes: alanyl aminopeptidase (AAP), leucyl aminopeptidase (LAP), acid phosphatase (AcP) and β-N-acetylglucosaminidase (NAG). Rainbow trout were divided into experimental groups: unvaccinated control, vaccinated uninfected, unvaccinated infected and vaccinated infected. The fish were orally immunised with a Y. ruckeri vaccine and challenged with a virulent strain of Y. ruckeri. The results showed significant differences in lysosomal enzyme activity between groups, indicating that vaccination modulated the hepatic autophagic response during bacterial infection. AAP and LAP activity peaked in unvaccinated infected fish, whereas vaccinated fish exhibited a blunted enzymatic response, suggesting that vaccination attenuated excessive autophagic activation. Similarly, AcP and NAG activity patterns indicated an infection-induced autophagic response that was partially attenuated in vaccinated fish. These results suggest that vaccination influences autophagy-related enzymatic activity in the liver of rainbow trout, potentially enhancing pathogen clearance while preventing excessive cellular stress. Understanding the interplay between vaccination, infection and autophagy may provide valuable insights to optimise vaccination strategies and improve disease management in aquaculture.