Pathogenic potential to humans of Shiga toxin-producing Escherichia coli isolated from wild boars in Poland.

The aim of the study was to investigate the presence of Shiga toxin-producing Escherichia coli (STEC) in the wild boar population of north-eastern Poland, and to evaluate the potential health risk associated with wild boars carrying STEC/AE-STEC strains. In Poland, the African Swine Fever (ASF) virus has been a growing problem in domestic pigs and wild boars, one of the main reservoirs of the virus, because of this hunters, veterinary practitioners and foresters thus face a greater risk of coming into contact with animals. Rectal swabs samples were obtained from 152 wild boars hunter-harvested in the 2017/2018 season (autumn-winter) in north-eastern Poland. The samples were enrichment in modified buffered peptone water. Polymerase chain reaction (PCR) assays were conducted to determine the virulence profile of stx1, stx2 and eae and aggR genes, identify subtypes of stx1 and stx2 genes, and perform O and H serotyping. STEC/AE-STEC virulence genes were detected in 43 isolates (28.29%): STEC in 17 isolates (11.18%) and AE-STEC in 26 isolates (17.11%), respectively. None of the tested isolates carried the aggR gene. The most dangerous AE-STEC virulence profile associated with HUS was found in 2 isolates (1.32%): stx1NS/stx2a/d/eae serotype ONT:H7 and stx2a/eae serotype O146:H7. Six of the 152 tested samples belonged to serogroup O157 (3.95%), including one AE-STEC isolate with virulence profile stx2g/eae and five EPEC isolates. The results of this study suggest that wild boars in north-eastern Poland can carry STEC/AE-STEC strains that are potentially pathogenic for humans. This is the first report documenting the virulence of STEC and AE-STEC isolates from wild boars in Poland.

Effect of feed supplementation with kynurenic acid on the morphology of the liver, kidney and gills in rainbow trout (Oncorhynchus mykiss Walbaum, 1792), healthy and experimentally infected with Yersinia ruckeri.

Kynurenic acid (KYNA) is an endogenous substance produced on the kynurenine pathway which is primarily known for its neuroactive properties. Recently, it has been proven that KYNA is a selective ligand for G protein-coupled receptor (GPR 35), presented on immunocompetent cells such as T lymphocytes. This opens up new possibilities of its application as an immunostimulating substance in aquaculture. Thus far, no histopathological investigations in fish have been completed to evaluate influence of KYNA supplementation in feed. This study has been undertaken to determine the effect of feed supplementation with KYNA (2.5, 25, 250 mg kg-1 of feed) for 28 days on the liver, gills and kidney in healthy fish and experimentally infected with Yersinia ruckeri. In a control group were observed a fatty liver, which is natural for this fish species in the autumn and winter season. As the dose of the supplement was increased, the fat liver changed, it decreased or completely disappeared. Additionally, inflammatory changes occurred in all the analysed organs, and their intensification was dose dependent. In the fish experimentally infected, KYNA caused aggravation of the signs in the liver, kidneys and gills, and the effect was dose dependent. The results implicate that KYNA may be a stressor for fish.

Characterization of Yersinia enterocolitica strains potentially virulent for humans and animals in river water.

AIMS: The aim of this study was to isolate and identify potentially pathogenic strains of Yersinia enterocolitica in water samples collected from the upstream section of the Drweca River in Poland. METHODS AND RESULTS: Thirty-nine water samples were collected. Strains were isolated, identified with the use of the API(®) 20E test kit (Biomerieux, Marcy l'Etoile, France) at 37°C, serotyped and subjected to a molecular analysis. Multiplex PCR was carried out to amplify three virulence genes: ail, ystA and ystB. Fragments of ail and ystA genes were not identified in the genetic material of the analysed strains. The ystB gene was identified in four strains. Yersinia enterocolitica strains of biotype 1A, which contain the ystB gene, may cause gastrointestinal problems. CONCLUSIONS: In our study, Y. enterocolitica strains of biotype 1A/ystB with serotypes 0 : 3, 0 : 5 and 0 : 8 were identified in samples collected from the Drweca River which flows through the areas protected by Natura 2000, one of the largest networks of nature conservation areas in the European Union. The presence of Y. enterocolitica in the Drweca River indicates that the analysed bacteria colonize natural water bodies. SIGNIFICANCE AND IMPACT OF THE STUDY: Most research focuses on food or sewage as a source of Y. enterocolitica infections. Little is known about the occurrence of this pathogen in natural waters. Our results show that natural waters are also a potential threat to human and animal health.

Application of DNA vaccines in fish.

Vaccination is a most cost-effective way of controlling infectious diseases in fish. However, some vaccination techniques when applied to hatchery conditions are not as effective as we expect them to be. Modern molecular biology techniques offer a number of opportunities for improving existing bacterial or viral vaccines or creating new ones. One of the most promising trends in vaccinology is development of DNA vaccination. DNA vaccines are based on the gene encoding specific antigen, which is expressed in vaccinated organism and induces the host immune system. DNA vaccines, compared to conventional vaccines, have many advantages including ability to trigger wider immune response, bigger stability and possibility of large-scale production. To date, there are several reports indicating effectiveness of DNA vaccines used against fish pathogens.

Modulative influence of lysozyme dimer on defence mechanisms in the carp (Cyprinus carpio) and European sheatfish (Silurus glanis) after suppression induced by herbicide Roundup.

Immunomodulation is a commonly used method of prophylaxis in humans and animals. Lysozyme dimer (KLP-602) was used at a dose of 50 ug/kg b.w. in order to correct the immunosuppression caused by the action of herbicide glyphosate (Roundup- Monsanto), which was used in a single bath for 10 minutes in a concentration of 100 mg/l of water. The investigations were carried out on 2 species of fish: the carp (Cyprinus carpio L.) and european catfish (Silurus glanis L.). Herbicide glyphosate caused a decrease in metabolic and phagocytic activity (RBA and PKA) and in proliferative response stimulated by Con A and LPS in carp and european catfish. The immunosuppression sustained for about 2 weeks. The results obtained indicate the possibility of correction of immunosuppression applying lysozyme dimmer (KLP-602) after use of which, the level of the studied indexes increased.

Effects of the herbicide Roundup on the ultrastructural pattern of hepatocytes in carp (Cyprinus carpio).

Experimental studies were performed on healthy, 80-100 g carp (Cyprinus carpio). Fish were exposed by emersion in Roundup (205 mg of glyphosate/l or 410 mg of glyphosate/l) in concentrations of 40- to 20-fold lower than those used in practice. Electron microscopy revealed that the herbicide caused appearance of myelin-like structures in carp hepatocytes, swelling of mitochondria and disappearance of internal membrane of mitochondria in carp at both exposure concentrations. It means that Roundup was harmful to carp when used in applied concentrations. Results of these studies enhance our knowledge of ultrastructural pathomorphology of fish organs following exposure to Roundup.

Effects of iridovirus-like agent on the cell-mediated immunity in sheatfish (Silurus glanis)--an in vitro study.

An iridovirus-like agent was tested for the first time in vitro on cell-mediated immunity in sheatfish (Silurus glanis). The influence of the iridovirus-like agent on pronephric macrophage metabolism was examined at two temperatures, 20 and 30 degrees C, by studying the respiratory burst activity stimulated by phorbol myristate acetate as well as the proliferative ability of lymphocytes stimulated by concanavalin A (ConA) and lipopolysaccharide (LPS) measured by MTT assay. The results showed that the iridovirus-like agent decreased the macrophage activity at incubation temperatures of 20 and 30 degrees C. The highest inhibitory effect was observed at 30 degrees C. The proliferative ability of pronephric lymphocytes had a similar pattern. The results showed that applying a virus at the same time or after the mitogen at 20 and 30 degrees C decreased the lymphocyte proliferation that was stimulated by either ConA or LPS. The highest suppressive effect was observed when virus was applied 14 h after the mitogen. This preliminary in vitro study demonstrated a strong suppressive influence of the iridovirus-like agent on pronephric macrophage and lymphocyte activity in sheatfish.