Isolation and Antimicrobial Resistance of Staphylococcus spp. in Freshwater Fish and Greek Marketplaces

The presence and antibiotic resistance of Staphylococcus spp. in freshwater fish and the environment of fish markets of Northern Greece were investigated. A total of 269 samples were examined, consisting of 71 rainbow trout (Oncorhynchus mykiss), 65 gibel carp (Carassius gibelio), and 133 environmental samples swabbed from various surfaces at fish markets.Staphylococcus spp. was isolated from 27% of the samples, and 16%, 9%, 0.7%, 0.4% and 0.4% were found to be positive for S. aureus, S. epidermidis, S. warneri, S. hominis-hominis, and S. haemolyticus, respectively. All isolates were examined for their susceptibility to 20 antibiotics. None of the S. aureus isolates were resistant to oxacillin and glycopeptides. Three S. epidermidis, two S. Warneri, and one S. haemolyticus isolates were resistant to oxacillin (methicillin resistant Staphylococcus, MRS). All isolates, except one, showed resistance to as many as 15 antibiotics. The population of Staphylococcus spp. in fish did not exceed 1.0 log CFU/g. Freshwater fish and the environments of retail fish markets were found to harbor multi-drug resistant staphylococci. Whether these findings present a real health risk for humans and to what extent needs to be evaluated.     

Effect of Trisodium Phosphate or Water Dip on the Survival of Salmonella and Listeria monocytogenes Inoculated Catfish Before and After Freezing

Salmonella and Listeria monocytogenes (LM) are occasional contaminants on raw fish. Catfish fillets were artificially contaminated with LM and Salmonella, dipped in a 1.5 % (30 min) trisodium phosphate solution (TSP), and cryogenically frozen. After 3 months frozen storage, Salmonella (2 log), but not LM, was inactivated on the fillets treated with the dip. This indicates that TSP dip followed by cryogenic freezing can be used to control Salmonella, but not LM, on catfish fillets.     

Antimicrobial Activity of Selected Essential Oils on Pseudomonas Species Associated with Spoilage of Fish with Emphasis on Cinnamon Essential Oil

ABSTRACT

Eight plant essential oils (cardamom, cinnamon, clove, eucalyptus, lemongrass, lime, nutmeg and rosemary) were evaluated for their antimicrobial activity against three Pseudomonas species associated with microbial spoilage of refrigerated tilapia. In vitro test of the essential oils, using disc-diffusion method, showed various degrees of antimicrobial activity against the Pseudomonas species. Cinnamon essential oil (CEO) had the highest antimicrobial activity, followed by clove essential oil. The remaining essential oils showed consistently weak activity. The antimicrobial efficiency of CEO against the Pseudomonas species was confirmed by potential minimum inhibitory concentration and minimum bactericidal concentration values, ranging between 0.125 and 0.375 µL/mL and 0.250–0.500 µL/mL, respectively. The anti-Pseudomonas activity of CEO was also tested in fish extract model at refrigeration temperature. The essential oil reduced the Pseudomonas viable count in fish extract but to a lesser extent than when it was applied at the same concentrations in culture medium. The chemical composition of CEO showed that the oil contained 79.1% cinnamaldehyde, which was suggested to be responsible for its antimicrobial activity. These results revealed the potential of CEO as a promising natural antimicrobial agent that could efficiently contribute to the control of spoilage bacteria and retard microbial spoilage of fresh fish.     

A Laboratory Based Study on the Accumulation and Excretion of Listeria spp. in King Salmon (Oncorynhus tshawytscha)

King (Chinook) salmon (Oncorhynchus tshawytscha) were exposed to salmon feed that had been inoculated with a strain of Listeria innocua. Viable Listeria cells could be isolated for the gut for at least 96 hr after the fish were expose to the feed. Listeria was isolated form the watercolumn, but not from the surface of the fish. The implications of these results on the production of cold smoked salmon is discussed.     

人工育苗条件下的大黄鱼胚胎发育及其仔,稚鱼形态特征与生态的研究

连续观察人工育苗中同一批受精卵,在水温23.2～23.4、盐度27.00～27.80‰条件下,经过3h36min孵出仔鱼,并继续观察仔、稚鱼发育过程中的形态特征与生态习性。还比较了不同年份与不同批次的观察资料,讨论了水温等环境条件变化对胚胎发育的影响,以及仔、稚鱼器官发育与日龄、生长速度等关系。     

Visualization of the respiring bacteria in sediments inhabited by Capitella sp. 1

ABSTRACT:    We used the tetrazolium salt 2-( p -iodophenyl)-3-( p -nitrophenyl)-5-phenyl tetrazolium chloride (INT) to locate sites of active (respiring) bacterial populations in sediments inhabited by the deposit-feeding polychaete Capitella sp. 1. In sediment microcosms, this organism created typical protruding tubes on the sediment surface and burrows from day 1. Within a couple of hours after adding INT into the overlying water, the red color of the reduced form of INT (INT-formazan) became apparent in the water column and on the sediment surface. During the following 24 h, part of the subsurface burrows turned red and the color of formazan intensified with time during incubation. Spatial heterogeneity of the distribution of the formazan deposits along burrows also was recognized. Microscopic observations revealed that the tubes and feces produced by Capitella sp. 1, as well as detrital particles, were the sites of intensive formazan deposition. Observation with higher magnification (up to ×1250) revealed that INT-formazan was present either as bacterial intercellular deposits or as microgranules covering entire bacterial cells. In situ application of INT into a sediment microcosm provides a simple and sensitive way to visualize the impact of burrow structures created by small macrobenthos, such as Capitella , on the distribution of metabolically active bacteria.     

山姜对益生芽孢杆菌体外抑菌活性试验研究

为研究中草药山姜粗提液对益生芽孢杆菌体外抑菌效果,特采用试管二倍稀释法和管碟法检测不同浓度的山姜煎煮液和乙醇提取液在体外对蜡样芽孢杆菌PAS38菌株和枯草芽孢杆菌Pab04菌株的最小抑菌浓度(MIC)和抑菌直径,并以肠毒性大肠杆菌(ETEC)、4μg/mL硫酸庆大霉素作阳性对照,生理盐水作阴性对照。结果表明,山姜煎煮液和乙醇提取液对两株益生芽孢杆菌和ETEC无抑菌作用,硫酸庆大霉素对蜡样芽孢杆菌PAS38和枯草芽孢杆菌Pab04菌株MIC均为1.25μg/mL,对ETEC的最低抑菌浓度MIC为0.625μg/mL。山姜煎煮液和乙醇提取液对受试菌株抑菌直径与生理盐水相比差异不显著(P>0.05),硫酸庆大霉素与其相比差异极显著(P<0.01)。山姜粗提液对两株益生芽孢杆菌无明显抑菌作用。     

"浦江一号"团头鲂与普通团头鲂亲本繁殖力及鱼苗培育对比试验

“浦江一号”团头鲂与普通团头鲂进行亲本繁殖及鱼苗培育的对比试验结果表明:“浦江一号”团头鲂相对产卵量为普通团头鲂的1．3倍,催产率、受精率、出苗率分别比普通团头鲂的高10．8％、5．2％、12．0％。经过一个月的培育,“浦江一号”团头鲂鱼苗平均成活率、平均体重分别比普通团头鲂高6．9％、20．9％。     

Effect of a constant magnetic field on water quality and rearing of European sheatfish Silurus glanis L. larvae

The influence of a constant magnetic field with an intensity ranging from 0.4 to 0.6 T (Tesla) was determined on physicochemical parameters of water and on rearing of larvae of the European sheatfish Silurus glanis L. larvae. In the experiment, feeding brood of European sheatfish was reared in two groups. One was kept in tanks supplied with magnetically treated water. The second group was kept in tanks supplied with water without treatment with a magnetic field (control). The fish tanks were supplied with circulating river water. Rearing was conducted for 15 days at an initial stocking density for both groups of 8 fish per litre. The mean fish mass obtained was 0.46 g, and in the control group – 0.78 g (P<0.05). Stocking mortality was 19.1% in the tanks with a constant magnetic field, and 13.5% in the control group. No changes were observed in water phosphate, ammonium, organic compounds or chloride concentrations.     

V_(B12)V_(B1)对扁藻繁值和生长的影响实验

对比实验表明,V_B_(12)、V_B_1对扁藻的生长无明显影响,不是扁藻生长必需的外源性有机营养。打破了V_B_(12)、V_B_1对单胞藻类生长有明显促进作用的传统结论。     

Influence of replacing fish meal with enzymatic hydrolysates of defatted silkworm pupa (Bombyx mori L.) on growth performance,body composition and non‐specific immunity of juvenile mirror carp (Cyprinus carpio var. specularis)

This study was conducted to investigate the effects of dietary supplementation of enzymatic hydrolysates of defatted silkworm pupa (EHDSP) on growth performance, body composition and non‐specific immunity of juvenile mirror carp (Cyprinus carpio var. specularis). The control diet (EHDSP0) was produced using fish meal (FM) as the main protein source and the other four diets were formulated by substitution of 25% (EHDSP25), 50% (EHDSP50), 75% (EHDSP75) and 100% (EHDSP100) FM with EHDSP. Five groups containing 270 juvenile mirror carp (14.51 ± 0.03 g) were fed to apparent satiation for 8 weeks. The results indicated that the special growth rate, weight gain, protein efficiency ratio and feed conversion rate of experimental fish in EHDSP25 and EHDSP50 groups were not significantly different from EHDSP0 group (p > .05). The spleen index of experimental fish in EHDSP25 group was significantly higher than that of EHDSP0 group (p < .05). The muscle protein content of experimental fish in EHDSP25 and EHDSP50 groups was significantly higher than that of EHDSP0 group (p < .05). Serum alanine aminotransferase and total cholesterol of experimental fish fed with the EHDSP were significantly lower than that of control (p < .05). The activity of serum superoxide dismutase of experimental fish in EHDSP25, EHDSP50 groups was significantly higher than that of EHDSP0 group (p < .05). Intestinal trypsin activity of EHDSP25 group was significantly higher than that of EHDSP0 (p < .05). In conclusion, EHDSP can be included into diet to replace 50% FM of juvenile mirror carp without negative effect on growth, furthermore, it can improve the non‐specific immunity and function of intestinal tract.     

Effect of replacing dietary fish meal with black soldier fly larvae meal on growth and fatty acid composition of Jian carp (Cyprinus carpio var. Jian)

To explore the effect of replacing dietary fish meal (FM) with black soldier fly (Hermetia illucens) larvae meal (BSFLM) on growth and body composition of Jian carp (Cyprinus carpio var. Jian), the FM in basal diet of Jian carp was replaced by 0, 35, 70, 105 and 140 g/kg BSFLM respectively to form five isonitrogenous and isolipidic diets. A total of 300 Jian carp (10.1 ± 1.6 g) were randomly divided into five groups (triplicate per group) and fed five diets, respectively. After 56 days of feeding, growth and body composition of fish were determined. Results showed that serum maleic dialdehyde, total antioxidant capacity, 18:1n‐9, 18:2n‐6, 20:5n‐3 and 22:6n‐3 in fish significantly decreased and 12:0, 14:0 and 16:0 significantly increased with increasing replacement of BSFLM. The growth, biological parameters, proximate composition, amino acid composition and serum biochemical parameters of Jian carp were not affected by the replacement of BSFLM. In conclusion, up to 140 g/kg BSFLM (100% replacement of FM) can be included in diets of Jian carp without unfavourable effects on growth while decreasing n‐3 highly unsaturated fatty acid (HUFA) composition in body of fish, suggesting that BSFLM could be used after nutrient enrichment with n‐3 HUFA to bring active effects on fish quality.     

Karyotype analysis of Oreochromis mossambicus,O. urolepis hornorum and their hybrid based on Cot‐1 DNA bands by fluorescence in situ hybridization

Chromosomal karyotypes of Oreochromis mossambicus and O. urolepis hornorum and their hybrid were analysed by means of Cot‐1 DNA bandings through fluorescence in situ hybridization (FISH). To identify all chromosomes, Cot‐1 DNA – which contains highly and moderately repetitive DNA – was extracted from genomic DNA, labelled as a probe with Dig‐11‐dUTP, and in situ hybridized to spreads of mitotic chromosomes of the three samples. The hybridized signals were detected by means of Cy3‐conjugated antidigoxigenin. The FISH results indicated that the three samples had the same diploid number (2n=44) of chromosomes. Specific fluorescence signal bands were detected on all individual chromosome pairs. On the basis of Cot‐1 DNA FISH banding patterns and chromosome morphology, the karyotypes of the three samples have been constructed; no remarkable differences were detected between the karyotypes of these species using this method. These results – which are similar to those reported previously, with respect to chromosome number, morphology and Cot‐1 DNA FISH patterns – suggest chromosomal stasis during speciation and hybridization of tilapia (Oreochromis, Cichlidae). Such a molecular cytogenetic procedure, if used in conjunction with other genomic research methods, could facilitate the study of genomic structure and be adapted for chromosome studies of other animal species.