Göran Bylund

Immune enhancement in rainbow trout (Oncorhynchus mykiss) by potential probiotic bacteria (Lactobacillus rhamnosus)

The present study assessed the immune enhancement of fish by a lactic acid bacterium (LAB) Lactobacillus rhamnosus (ATCC 53103). The bacterium was administered orally at five different doses 7.9 x 10(4) (LAB4), 2.1 x 10(6) (LAB6), 2.8 x 10(8) (LAB8), 1.9 x 10(10) (LAB10) and 9.7 x 10(10) (LAB11) CFU/g feed to rainbow trout for two weeks and the feed was changed to un-supplemented diet. From the onset of feeding supplemented diets at 1, 2, 3 and 4 weeks, blood and mucus samples were taken. During the LAB feeding period L. rhamnosus persisted in the fish intestine and in the tank water in high numbers. However, L. rhamnosus disappeared from the intestine, skin mucus and tank water within one week after the change to the non-supplemented feed. In comparison to untreated control fish, respiratory burst activity of blood cells was raised significantly in the LAB4 treated group on week 2. Serum-mediated killing of Escherichia coli was increased significantly in group LAB6 on week 2. Serum immunoglobulin levels were significantly raised only in LAB8 group on week 1 and in LAB4 and LAB8 at the end of the trial. The results show that rainbow trout immune parameters were enhanced by using probiotic bacteria.

Protection of rainbow trout (Oncorhynchus mykiss) from furunculosis by Lactobacillus rhamnosus

The present study aimed to investigate the potential probiotic properties in fish of a lactic acid bacterium intended for human use: Lactobacillus rhamnosus (ATCC 53103). A probiotic for human use was specifically chosen since it is known to be safe for human use, which is of major importance because the fish are meant for human consumption. The bacterium was administered at two different doses (109 and 1012 CFU/g feed) to rainbow trout for 51 days. Sixteen days after the start of the Lactobacillus feeding, the fish were challenged with Aeromonas salmonicida ssp. salmonicida, which causes furunculosis. During the challenge trial the mortality was monitored. L. rhamnosus reduced the fish mortality significantly, from 52.6% in the control to 18.9% and 46.3% in the 109 CFU/g feed and the 1012 CFU/g feed groups, respectively. From this, it was concluded that the tested strain may be a promising probiotic for fish without subsequent risk for human consumption.

Characterization of the Properties of Human- and Dairy-Derived Probiotics for Prevention of Infectious Diseases in Fish

ABSTRACT The present study aimed to investigate the potential probiotic properties of six lactic acid bacteria (LAB) intended for human use, Lactobacillus rhamnosus ATCC 53103,Lactobacillus casei Shirota, Lactobacillus bulgaricus, L. rhamnosus LC 705, Bifidobacterium lactis Bb12, and Lactobacillus johnsonii La1, and one for animal use, Enterococcus faecium Tehobak, for use as a fish probiotic. The strains for human use were specifically chosen since they are known to be safe for human use, which is of major importance because the fish are meant for human consumption. The selection was carried out by five different methods: mucosal adhesion, mucosal penetration, inhibition of pathogen growth and adhesion, and resistance to fish bile. The adhesion abilities of the seven LAB and three fish pathogens, Vibrio anguillarum, Aeromonas salmonicida, and Flavobacterium psychrophilum, were determined to mucus from five different sites on the surface or in the gut of rainbow trout. Five of the tested LAB strains showed considerable adhesion to different fish mucus types (14 to 26% of the added bacteria). Despite their adhesive character, the LAB strains were not able to inhibit the mucus binding of A. salmonicida. Coculture experiments showed significant inhibition of growth of A. salmonicida, which was mediated by competition for nutrients rather than secretion of inhibitory substances by the probiotic bacteria as measured in spent culture liquid. All LAB except L. casei Shirota showed tolerance against fish bile. L. rhamnosus ATCC 53103 and L. bulgaricus were found to penetrate fish mucus better than other probiotic bacteria. Based on bile resistance, mucus adhesion, mucus penetration, and suppression of fish pathogen growth,L. rhamnosus ATCC 53103 and L. bulgaricus can be considered for future in vivo challenge studies in fish as a novel and safe treatment in aquaculture.

Residues of oxytetracycline in wild fish and sediments from fish farms.

Abstract The residues and persistence of oxytetracycline were studied in wild fish and sediments on two fish farms after chemotherapy of the farmed fish. In wild fish, residues of oxytetracycline were detected up to 13 days after the medication. The half-life of oxytetracycline in fish farm sediments was 9 days and 419 days on the two farms, respectively. The results indicate that oxytetracycline may, under stagnant anoxic conditions, be very persistent in fish farm sediments. It is suggested that leakage from sediments, not decomposition, may be the main factor reducing the oxytetracycline levels in sediments. Bacteria, resistant to oxytetracycline, were isolated from the intestines of wild fish.

Residues of oxolinic acid and oxytetracycline in fish and sediments from fish farms

Abstract The residues of oxolinic acid and oxytetracycline were studied in fish and sediments from five fish farms after chemotherapy of the farmed fish. Compared to oxytetracycline, oxolinic acid was better absorbed and faster excreted from the treated fish. Oxytetracycline was found persistent in concentrations of 0.8–6.3 μg/g in the sediments under the medicated fish pens. Oxolinic acid levels of 0.05–0.2 μg/g were measured in the sediments for 5 days after the treatment of the fish. Compared to oxytetracycline, oxolinic acid showed a faster loss of antibacterial activity in the fish farm sediments. Fish pathogenic bacteria resistant to oxytetracycline were isolated from the treated fish and from the sediments under fish pens. No fish pathogenic bacteria resistant to oxolinic acid were found in this study.

Temperature-related absorption and excretion of oxytetracycline in rainbow trout (Salmo gairdneri R.)

Abstract The absorption and elimination of oxytetracycline in serum, muscles and liver of rainbow trout were studied at 5°, 10° and 16°C after a single oral dose of 75 mg/kg fish. The absorption of the drug was relatively rapid, with maximum concentrations reached in serum within 1 h at 16°C, 12 h at 10°C and 24 h at 5°C. The highest drug levels were measured in bile and liver followed by serum and muscle tissue. The elimination of the drug was markedly temperature-dependent. The half-life of oxytetracycline in rainbow trout serum was 4.8 days at 16°C, 6.1 days at 10°C and 8.9 days at 5°C. The predicted withdrawal times varied from 27 days to 135 days depending on temperature and tissue studied. Results obtained from laboratory experiments are compared with results from field trials.

Temperature-related absorption and excretion of oxolinic acid in rainbow trout (Oncorhynchus mykiss)

Abstract The absorption and elimination of oxolinic acid in serum, bile and tissues of rainbow trout were studied at 5, 10 and 15 °C after a single oral dose of 75 mg/kg. The maximum levels of oxolinic acid were obtained in serum within 1, 4 and 6 days at 16, 10 and 5 °C, respectively. The highest drug concentrations were measured in bile followed by liver, kidney, muscle tissue and serum. The higher levels of oxolinic acid in tissues compared to serum indicate a good distribution of the drug. The elimination half-life in serum was 24 h at 16 °C, 4.0 days at 10 °C and 6.1 days at 5 °C. With the detection limit of 0.01 μg/g for the oxolinic acid HPLC assay, the predicted withdrawal time with 95% confidence for muscle tissue was 28 days at 16 °C, 60 days at 10 °C and 140 days at 5 °C. Results obtained under laboratory conditions were in accordance with results from field trials.

EFFECT OF FLORFENICOL ON THE IMMUNE RESPONSE OF RAINBOW TROUT (ONCORHYNCHUS MYKISS)

Florfenicol, a drug effective against several bacterial diseases of fish, was tested for possible immunomodulatory effects. The aim of the study was to follow the kinetics of the immune response after vaccination with simultaneous oral antibiotic treatment. The fish were immunised with a commercial oil-based divalent (furunculosis/vibriosis) vaccine and were simultaneously given oral antibiotic treatment. The specific immune response was monitored by analysing the levels of specific antibodies with ELISA. As an indicator of the non-specific immune response the phagocytic activity of circulating leucocytes was measured by a chemiluminescence assay. Total circulating leucocyte counts and differentials were also monitored. The disease resistance was evaluated by challenge tests at the end of the experiment. The results showed that florfenicol did not have any significant effect on antibody production and circulating leucocyte levels but caused a suppression in chemiluminescence response/phagocytic cell 5-6 weeks after vaccination. The survival after challenge was slightly suppressed by the florfenicol treatment. The RPS-value for the vaccinated group was 98% and for the florfenicol-treated group was 88%.

Respiratory burst activity of rainbow trout (Oncorhynchus mykiss) phagocytes is modulated by antimicrobial drugs

Abstract In vitro and in vivo effects of five different antimicrobial drugs on the chemiluminescence (CL) response of phagocytes isolated from the blood and from the head kidney of rainbow trout ( Oncorhynchus mykiss ) were examined. Opsonized zymosan was used to stimulate the respiratory burst utilizing luminol and lucigenin as substrates. The drugs tested were: oxolinic acid (OA), oxytetracycline (OTC), florfenicol (FF) and sulphadiazine in combination with trimethoprim (SDZ/TMP) in ratio 5:1. In the in vitro test, the CL response was measured after a pre-incubation of head kidney and blood phagocytes for 2 and 24 h, with six different concentrations (0.1–100 μg ml −1 ) of each drug. The lucigenin-enhanced CL response of blood phagocytes was significantly suppressed by OA, OTC and SDZ/TMP at the highest concentration tested, but the luminol-enhanced response was unaffected. The lucigenin-enhanced CL response of head kidney phagocytes was significantly suppressed by SDZ/TMP at concentrations greater than 5 μg ml −1 and by OTC and FF at the highest concentration tested. For the in vivo tests, the fish were fed for 10 days with therapeutic doses of the drugs and the blood and head kidney phagocytes were isolated immediately after the drug exposure. SDZ/TMP stimulated the luminol-enhanced CL response of blood and head kidney phagocytes. FF had a suppressive effect on CL response with luminol and lucigenin on blood phagocytes. OA had a suppressive effect on lucigenin CL response in blood and head kidney phagocytes.

Protein profiles as an aid to taxonomy in the genus Diphyllobothrium

SummarySpecific and distinct protein profiles were demonstrated by isoelectric focusing performed on soluble whole-body proteins of four Diphyllobothrium species. The protein patterns differed in number, position and relative density of the fractions separated. Altogether 31–36 protein bands per species were separated by isoelectric focusing in thin-layer polyacrylamide gels. The results show that sensitive chemotaxonomic methods can be used to help characterize and delimit species in the troublesome Diphyllobothrium group.