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1.
ABSTRACT:   Antibiotic residues in marine sediments of fish farms negatively influence microbial ecologic systems. The microbial degradation of antibiotic residues was experimentally examined in the marine sediments of Uranouchi Bay, to which one of five antibiotics was added. After incubation reducing physical factors, ampicillin, doxycycline, oxytetracycline, and thiamphenicol were significantly degraded, while josamycin maintained most of the initial amounts. The isolates resistant to ampicillin, josamycin, oxytetracycline, or thiamphenicol degraded each antibiotic in wide ranges of degrees, whereas the isolates degrading doxycycline were not obtained. Microbial degradation may contribute to the disappearance of ampicillin, doxycycline, oxytetracycline, and thiamphenicol in the fish farm. In contrast, the disappearance of josamycin would depend on physical factors, but the bacteria degrading josamycin at least exist in the marine sediments. Phylogenetic analysis using 16S rDNA sequences demonstrated that the antibiotic-resistant isolates formed several clusters in the Gram-positive bacterial group, the Flavobacterium–Cytophaga–Bacteroides group, and the proteobacteria subdivisions. The antibiotic-resistant bacterial population would be composed of various species including ubiquitous coastal bacterial groups. Several species of antibiotic resistant bacteria show antibiotic degradation activities, and appear to contribute to the disappearance of antibiotics in Uranouchi Bay.  相似文献   

2.
ABSTRACT:   The concentration of aquatic bacteria is basic information required to evaluate the status of environments and to assess bacterial contribution to material cycles. However, the standard direct counting method using epifluorescence microscopy (EFM) is tedious and there is variation in the counts among workers. Here an automatic counting system that consists of Bioplorer (BP) and image analysis has been applied to marine bacteria. BP is composed of a light-emitting diode (LED) illuminant, an optical unit, a driving stage and a charge-coupled device camera. In combination with fluorescent labeling and simplified membrane filtration, bacteria are enumerated automatically. The reproducibility, sensitivity and accuracy of the system were tested for natural marine bacteria, in comparison with EFM and flow cytometry (FCM). The counts obtained by BP showed good correlation with those obtained by EFM and FCM methods. The counts were significantly higher in inshore and oceanic samples, indicating high sensitivity with low background noise. Considering its reproducibility, objectivity, ease of use and compact size, BP can be used as a routine tool for counting aquatic bacteria in substitution for EFM or FCM.  相似文献   

3.
Carps are the most diversified freshwater fish belonging to family Cyprinidae. Numerous probiotic and pathogenic lactic acid bacteria (LAB) have been characterized from carps. However, the diversity of these ecologically important bacteria is entirely unknown in freshwater fish of Pakistan. The present study aimed to characterize and identify the lactic acid bacteria from two carps viz. Laboe rohita and Cirrhinus mrigala and determine their antagonistic activity. Seventeen bacterial isolates were purified from the gastrointestinal tract and gills of these fish and characterized morphologically. Initially, seven isolates were screened as LAB using agar supplemented with CaCO3. Subsequently, only two isolates CILB2 and RIL10 were selected as LAB after high‐performance liquid chromatography analysis for lactic acid production. Isolates CILB2 and RIL10 were genetically identified as Enterococcus faecalis and Weissella sp., respectively after 16S rRNA gene sequence analysis. Both strains exhibited significant antagonistic activity against common fish pathogens Streptococcus agalactiae, Staphylococcus aureus and Escherichia coli. Enterococcus faecalis CILB2 and Weissella sp. RIL10 were also found negative for haemolysis and gelatinase activities and were sensitive to ampicillin, amoxicillin, doxycycline, erythromycin, chloramphenicol and co‐trimoxazole antibiotics. The identified LAB strains may further be investigated for their potential probiotic application in fish feed and food preservation techniques.  相似文献   

4.
ABSTRACT:   Among several marine antagonistic bacteria isolated from the sea water of Kagoshima Bay, Pseudoalteromonas sp. A1-J11 was found to produce anti- Vibrio substances. The anti- Vibrio substances were extracted from the culture supernatant of the strain with chloroform and isolated using reverse-phase (Cosmosil 75C18-OPN) column chromatography followed by high-pressure liquid chromatography (Mightysil RP-18 GP Aqua). Purified substances, designated as AVS-03 a , c and d showed similar ultraviolet absorption spectra with λmax at 215, 235, 315 and 327 nm in methanol. AVS-03 d , the major anti- Vibrio substance, was thermostable up to 100°C and pH stable over a pH range higher than 4.0, and also showed strong inhibitory activities, specifically against Vibrio harveyi strains.  相似文献   

5.
Use of antibiotics for the control of bacterial diseases in shrimp culture has caused several adverse impacts to the industry. This has resulted in the search for alternative environment friendly approaches to overcome bacterial infections. This study was conducted to investigate the use of beneficial bacteria as an alternative to antibiotics. Ten pathogenic bacterial species isolated from shrimp, Penaeus monodon, and Artemia cysts were tested for susceptibility to indigenous marine Bacillus subtilis AB65, Bacillus pumilus AB58, Bacillus licheniformis AB69 and compared with oxytetracycline, chloramphenicol, gentamicin and bacitracin, which are common antibiotics used in Asian aquaculture. The Bacillus spp. were isolated from the local marine environment for bioremediation use in shrimp hatcheries and were proven to reduce total ammonium nitrogen. The pathogenic bacterial isolates were 90% susceptible to B. subtilis AB65, 70% susceptible to B. pumilus AB58 and B. licheniformis AB69 and 100% susceptible to oxytetracycline, chloramphenicol and gentamicin but only 40% to bacitracin. Two representative isolates of the vibrio group, Vibrio alginolyticus VaM11 and Vibrio parahaemolyticus VpM1, when tested for competitive exclusion by a common broth method using the marine Bacillus spp., showed decreased viable counts from 10(8) to 10(2) cfu mL(-1). The results suggest that the action of the marine bacteria appears to be significant in protecting the host shrimp against pathogenic bacteria. In addition to the alternative use of antibiotics, the selected marine bacteria had additional bioremediation properties of reducing ammonia.  相似文献   

6.
The microenvironment of bacteria associated with the gastrointestinal tract of an animal influences the host in many ways, including the metabolism of several nutrients. Isolation, molecular characterization and enzymatic activities of culturable bacteria associated with the gastrointestinal tract of hatchery‐reared oceanic yellow seahorse, Hippocampus kuda, were investigated in the present study. 16S rRNA sequencing of bacterial isolates yielded 10 different bacterial genera belonging to two major groups: proteobacteria (62.9%) and firmicutes (37.03%). The predominant microbial flora belonged to the genera Vibrio spp., Enterovibrio sp. and Bacillus spp. Burkholderia cenocepacia, hitherto unreported from the gastrointestinal tract of marine fish, was retrieved from the seahorse gut, albeit in small numbers. Enzymatic studies indicated that the bacterial isolates possess the ability to degrade lipids, cellulose, xylan, starch and proteins. Lipase activity was exhibited by a majority of the isolates (70.4%), indicating that the bacterial flora associated with the intestinal tract of seahorses is capable of digesting foods rich in lipids. The possible implications for the role of these bacteria in the digestion and physiological processes are discussed. To our knowledge, this is the first time that the characterization and enzymatic activities of bacteria associated with the intestinal tract of farmed seahorses have been reported.  相似文献   

7.
Salt fermented fish hydrolysate (SFFH) was prepared from freshwater fish Rohu (Labeo rohita), an Indian major carp, using salt at room temperature for 50 days. Total lactic acid bacteria (LAB) counts of SFFH prepared using 20% and 30% NaCl (w/w) were found to be in the range of 5.83–7.25 log cfu/ml and 3.93–5.46 log cfu/ml, respectively, whereas the log cfu/ml values for the halotolerant LAB counts varied from 2.09 to 7.17 and 2.02 to 4.77, respectively. Out of 96 isolates from SFFH, 21 isolates were screened based on their pH reducing ability, total titratable acidity, and proteolytic properties. Morphological, biochemical, and molecular characterization of four selected LAB strains were carried out. The isolates FSAP3-3 (Pediococcus pentosaceus), FSBP4-40 (Pediococcus pentosaceus), FSBP16-40 (Pediococcus pentosaceus), and FSBP28-50 (Pediococcus acidilactici) showed both halotolerant and proteolytic properties. The identified LAB isolates showed antagonistic properties against several human pathogens and exhibited sensitivity toward a broad spectrum of antibiotics. All the identified LAB isolates showed excellent proteolytic activity and phosphohydrolase activity. These halotolerant LAB isolates that had both proteolytic properties and acidifying ability have the potential for application in an acceleration of fermentation to produce salted fish products (i.e., fish sauce, fish paste, fish mince, etc.).  相似文献   

8.
Since its first outbreak in Japan in 2003, koi‐herpesvirus (KHV) remains a challenge to the carp Cyprinus carpio L. breeding industry. In this study, inactivation of KHV in water from carp habitats (carp habitat water) was investigated with the aim of developing a model for rapidly inactivating the pathogen in aquaculture effluent. Experiments with live fish showed that, in carp habitat water, KHV lost its infectivity within 3 days. Indications were that inactivation of KHV was caused by the antagonistic activity of bacteria (anti‐KHV bacteria) in the water from carp habitats. Carp habitat water and the intestinal contents of carp were therefore screened for anti‐KHV bacteria. Of 581 bacterial isolates, 23 showed anti‐KHV activity. An effluent treatment model for the disinfection of KHV in aquaculture effluent water using anti‐KHV bacteria was developed and evaluated. The model showed a decrease in cumulative mortality and in the number of KHV genome copies in kidney tissue of fish injected with treated effluent compared with a positive control. It is thought that anti‐KHV bacteria isolated from the intestinal contents of carp and from carp habitat water can be used to control KHV outbreaks.  相似文献   

9.
Probiotic potential of the autochthonous bacteria in catla, Catla catla has been evaluated through determination of antagonistic activity (in vitro) of the cellular components of gut bacteria against seven fish pathogens. Altogether 208 strains were isolated, inhibitory activity of the isolates was evaluated through cross‐streaking and 16 primarily selected antagonistic strains were confirmed using the double‐layer method. Four bacteria that showed antagonism against ≥4 pathogens were selected as putative probiotics. The intracellular, extracellular, whole‐cell and heat‐killed cell components exhibited bactericidal activity against the pathogens. In addition, the selected strains were capable of producing different extracellular enzymes, competent to grow in intestinal mucus and could tolerate diluted bile juice. Analysis of 16SrRNA partial gene sequence revealed that both the strains CC1FG2 and CC1FG4 were Bacillus methylotrophicus (KF559344 and KF559345), while the isolates CC1HG5 and CC2HG7 were Bacillus subtilis subsp. spizizenii (KF559346) and Enterobacter hormaechei (KF559347) respectively. Bio‐safety evaluation through intra‐peritoneal injection of the isolates did not induce any pathological signs or mortalities in C. catla. The study confirmed probiotic properties of autochthonous gut bacteria in C. catla and demonstrated potential for using them as bio‐control agents. However, in vivo studies are essential to explore their efficacy in the commercial aquaculture.  相似文献   

10.
Fermentation using native lactic acid bacteria (LAB) was evaluated for its effectiveness in recovering lipids and proteins simultaneously from freshwater fish visceral waste (FVW). Five different LAB isolated from fish processing waste were employed in a fermentation process that involved 10% (w/w) glucose, 2% (w/w) NaCl, and 10% (v/w) LAB. Cultures evaluated included four native isolates (Pediococcus acidilactici NCIM5368, Enterococcus faecalis NCIM5367, Pediococcus acidilactici FM37, and Pediococcus acidilactici MW2) from FVW with E. faecium NCIM5335 as the reference culture. Fermentation with native LAB resulted in recovery of > 90% oil present in the material as against no recovery in case of raw (unfermented) viscera and resulted in > 50% of degree of hydrolysis of proteins. The fatty acid profile of lipids was not affected by the fermentation process. The fermentation liquor, rich in hydrolyzed protein, exhibited antioxidant as well as antagonistic properties against several bacterial pathogens. The results clearly demonstrate the usefulness of fermentation using native isolates for simultaneous recovery of lipids and proteins from fish processing waste. It also asserts the value of fermentation as an eco-friendly method and aids in minimizing disposal/pollution problems associated with these solid wastes.  相似文献   

11.
A selection of 16 field isolates of Photobacterium damselae from marine rainbow trout farms in Denmark was subjected to phenotypic and genotypic characterization and pathogenicity to fish. All isolates belonged to the subspecies damselae , being positive for haemolysis, motility and urease. There were considerable differences in haemolytic properties, some isolates presenting a broad zone of haemolysis and others only a narrow zone. Pulsed-field gel electrophoresis revealed a high diversity indicating that P. damselae subsp. damselae is an opportunistic, not clonal pathogen in Danish marine rainbow trout. Virulence of the strains to rainbow trout was highly variable with LD50 values ranging from 3.9 × 103 to 1.5 × 108 cfu at 20 °C. The virulence was significantly higher at 20 °C than at 13 °C. The strains with the strongest haemolytic properties were the most virulent suggesting a strong involvement of haemolysin in the pathogenesis. The pathological changes were consistent with a bacterial septicaemia and the haemorrhages were more pronounced than for most other bacterial infections.  相似文献   

12.
Aerobic heterotrophic bacteria were isolated from the intestinal contents of Atlantic salmon, Salmo salar , rainbow trout, Oncorhynchus mykiss , and turbot, Scophthalmus maximus , on tryptone soya agar and De Man Rogosa and Sharpe agar, of which 11 of 177 (6% of the total) of the isolates were antagonistic to Aeromonas salmonicida . Four of these cultures, which were identified tentatively as A. hydrophila , Vibrio fluvialis , Carnobacterium sp. and an unidentified Gram-positive coccus, were beneficial to fish when fed singly or as an equi-mixture. Feed supplemented with the putative probiotics indicated survival of the organisms in the gastrointestinal tract for 7 days. Feeding with the probiotics for 7 and 14 days led to better survival following challenge with A. salmonicida . There was no indication of serum or mucus antibodies to A. salmonicida , but there was an increased number of erythrocytes, macrophages, lymphocytes and leucocytes, and enhanced lysozyme activity in the fish.  相似文献   

13.
Fermented shrimp paste (Kapi) is traditionally produced using a high content of salt and mainly consumed as a food condiment by the Thai people. In order to select potential functional autochthonous starter culture, the protease-producing bacteria from Kapi were isolated, screened, and evaluated for technological and safety aspects. Among 195 isolates, five bacterial strains (MSK-3P, MSK-4P, MSK-5P, MSK-7P, and MSK-10P) exhibited the highest activity of protease using Anson method. All of them were identified as Virgibacillus halodenitrificans using 16S rRNA sequence analysis. All selected strains exhibited growth in the presence of NaCl up to 25%. Neither strain showed hemolytic activity nor biogenic amine formation. Among all selected strains, only strain MSK-10P had no ability to form a biofilm, while four other strains showed a weak ability. Strain MSK-7P exhibited multiple resistances to tetracycline and vancomycin, while strains MSK-3P, MSK-4P, and MSK-10P showed susceptibility to all antibiotics tested. According to the obtained results, this protease-producing V. halodenitrificans MSK-10P is a good candidate for further investigation for use in Kapi fermentation to assess its technological performance as a autochthonous starter culture.  相似文献   

14.
在零售市场和生产企业抽取4批真空包装淡腌青鱼,对其感官、化学和细菌学品质特性进行分析,并对细菌类型和数量进行研究。结果显示,产品栅栏因子及强度存在差异,盐分含量6.68%~12.06%,平均值(9.36±2.2)%;水分活度值0.75~0.91,平均值0.82±0.07;pH值6.00~6.30,平均值6.20±0.13。栅栏因子种类和强度的不同决定产品品质的差异,感官评价均可接受,过氧化值均值为19.65±8.75 meq/kg,挥发性盐基氮均值为24.50±15.30 mg/100 g,菌落总数均值为4.45±1.15 cfu/g,大肠菌群均低于30 MPN/100 g。从4批淡腌青鱼样品分离到234株细菌,73.9%是革兰氏阳性细菌,其中36.3%是葡萄球菌,31.6%是链球菌,并出现少量微球菌和棒状杆菌;由需氧革兰氏阴性杆菌不动杆菌、摩氏杆菌和鞘氨醇单胞菌组成较小的细菌菌群约占总细菌群落的18.4%,显示水分活度、盐分含量和pH值等栅栏因子与产品细菌类型和数量呈一定相关性。  相似文献   

15.
The aim of the study was to isolate, select, and identify proteolytic lactic acid bacteria (LAB) from chao, a traditional fermented fish from Pangkajene and Kepulauan Regency, South Sulawesi, Indonesia. LAB was isolated by poured plate method. Proteolytic LAB were selected using agar skim milk media. Protease activity of LAB was determined based on the amount of tyrosine released in unit/mL. Proteolytic LAB were identified using API 50 CHL kit and 16S rRNA gene sequence analysis. The result showed that a total of 60 isolates were obtained from chao, and 57% of them were cocci-shape. Fifteen isolates were halotolerant proteolytic LAB. Their R values and protease activity were 2.11–3.39 and 0.267–0.304 U/mL, respectively. Identification by API 50 CHL kit showed that four rod-shape isolates were Lactobacillus plantarum, and two others were Lactobacillus curvatus. Cocci-shape isolates could not be identified as cocci bacterium. Rep-PCR results showed that there were two kinds of bands, namely thick and thin. Two isolates were selected from two types of bands that had the highest R for the analysis of 16S rRNA gene sequences, namely Ags1-3 and Ags7-3. The results showed that Ags1-3 isolate was identified as Lactobacillus plantarum and Ags7-3 as Pediococcus acidilactici.  相似文献   

16.
Abstract. The transformation of Aeromonas salmonicida with DNA fragments from bacterial cell-free sonicates was investigated with intraspecific, interspecific band intergeneric fish pathogenic bacteria including Aeromonas salmonicida, Aeromonas hydrophila, Pseiidomonas fluorescens and Vibrio anguillarum strains as donor bacteria. A phenotypic marker for transformation was extracellular protease production since a protease-deficient mutant NTG-1 induced from pathogenic A. salmonicida strain A-7301 by mutagenesis was used as a recipient. This mutant was non-pathogenic to rainbow trout. The mutant was incubated with each sonicate at 20°C for 20 days with a nutrient-poor medium containing a trace (5 μg/ml each) of both humic acid and tryptone in the presence of clean river sand (100 g/100 ml medium) corresponding with an environment of rivers. During the incubation, the survival of mutant NTG-1 cells was observed and protease positive NTG-1 cells were isolated from each culture. The protease production of the isolates was due to the transmission of protease genes of the donor strains. The activity of proteases produced by the transformants extra-cellularly was determined. These transformants induced with the sonicates of the parent strain, intraspecific strain and with the sonicates of the interspecific A. hydrophila strain were pathogenic to rainbow trout, whereas the transformants derived with the sonicates of the intergeneric strains P. fluorescens and V. anguiUarum showed non-pathogenicity, although all the donor strains, with the exception of the P. fluorescens strain, were pathogenic. These findings are interesting since they demonstrate that trausformation in A. salmonicida occurs with considerable ease even intergenencally and interspecifically, as well as intraspecifically in river environments, and that there is a large difference in the lethal toxicity of extracellular protease produced by these bacteria.  相似文献   

17.
Streptococcus agalactiae is an emerging pathogen of fish and has caused significant morbidity and mortality worldwide. The main objective of this study is to assess whether pathogenic differences exist among isolates from different geographic locations. Nile tilapia (Oreochromis niloticus L.) were administered an intraperitoneal injection of suspension containing USA, Brazil, Honduras, Israel, or Kuwait S. agalactiae isolates at concentrations ranging from 102 to 107 cfu mL?1. The LD50 values 7 days after challenge were as follows: USA (1.0 × 102 cfu mL?1), Brazil (1.5 × 103 cfu mL?1), Honduras (6.8 × 103 cfu mL?1), Israel (1.0 × 104 cfu mL?1) and Kuwait (7.2 × 105 cfu mL?1). Fish from all groups exhibited lethargy, anorexia, exophthalmia, corneal opacity, erratic swimming, petechiae and mortality. Opercular clearing and ascites were only found after infection with certain geographic isolates. The findings in this study indicate that S. agalactiae isolates of different geographic origin can cause significant mortalities after experimental challenge and can have different pathogenic capacities. Isolates from the Americas (USA, Brazil and Honduras) were more pathogenic to Nile tilapia than isolates from the Middle East/Asia (Israel and Kuwait).  相似文献   

18.
Populations of aerobic heterotrophic bacteria present in the gastrointestinal (GI) tract of healthy Atlantic cod (Gadus morhua L.) fed three different diets, fish meal, standard or a bioprocessed soybean meal (BPSBM), were estimated using the dilution plate technique. A total of 944 isolates were characterised by biochemical and physiological properties and 425 isolates were identified further by sequencing the 16S rRNA genes. Our results showed that gut microbiota were affected by dietary manipulation. The GI tract of fish fed fish meal was dominated by Gram-positive bacteria of the genera Brochothrix and Carnobacterium. The Gram-negative bacteria Chryseobacterium spp. and Psychrobacter glacincola, and Gram-positive bacteria belonging to Carnobacterium, dominated in the digestive tract of fish fed soybean meal. In contrast to these results, genus Psychrobacter dominated in the GI tract when fish were fed BPSBM.Until recently, it was generally suggested that the gut microbiota of fish were less diverse than in homoeothermic animals. However, the present study identified several “new” bacterial species isolated from the alimentary tract of Atlantic cod. These “new” bacterial species are not normally isolated from the GI tract of fish. Based on our finding we suggest that the GI tract microbiota of fish might not be as simple as believed.Antagonistic activity of carnobacteria regarding inhibition of growth of two fish pathogens (Aeromonas salmonicida ssp. salmonicida and Vibrio anguillarum) was observed. However, some difference in the antibacterial activity of Carnobacterium spp. was observed. Whether this antagonistic activity has any effect in challenge studies will be discussed, especially in relation to the finding that the digestive tract is one of the major infection routes in fish.  相似文献   

19.
MAIDIE  ASFIE  TORU  YOSHIJIMA  HARUO  SUGITA 《Fisheries Science》2003,69(1):21-26
ABSTRACT:   Bacterial populations in goldfish feces were characterized by the fluorescent in situ hybridization (FISH) method. A total of nine different group-specific rRNA-targeted oligonucleotide probes were used. Approximately half of the microbial cells (57.8 ± 16.7%) were detected with a probe EUB338 and found to be bacteria. The microbial cells in 33–35 of the 35 samples from five specimens strongly hybridized with probes ALF1b, BET42a and GAM42a, suggesting that goldfish intestinal bacteria are mainly composed of α, β and γ-subclasses of Proteobacteria. The fact that a probe AER66 reacted with 25.6 ± 14.2% of the total microbial cells in all 35 samples, demonstrated that genus Aeromonas was the dominant species in the goldfish intestines. Genus Bacteroides including Bacteroides type A detected with a probe BAC303 was observed in 15 of 35 samples while other taxonomic groups determined with HGC69a, CF39a and P72 were detected in 6–11 of 35 samples. These results strongly suggest that Bacteroides shows the greatest daily fluctuation and interindividual variation in the intestines of goldfish. Moreover, the FISH method was proven to be useful for rapid enumeration of taxonomic groups of fish intestinal bacteria.  相似文献   

20.
The objective of this study was to evaluate the probiotic properties of lactic acid bacteria (LAB) strains isolated from digestive tract of white shrimp Litopenaeus vannamei. Eighteen LAB colonies were isolated and one bacterium was found capable of producing three extracellular enzymes (protease, cellulose and lipase) simultaneously and exhibited antagonistic activity against shrimp pathogens (Vibrio vulnificus, V. rotiferianus and V. campbellii). The putative probiotic strain AS13 was identified as Lactobacillus pentosus based on 16S rRNA sequencing. The L. vannamei were fed diet containing 0 (control), 106, 107 and 108 CFU g?1 bacterial cells of AS13 for 28 days. The results showed that supplementation of L. pentosus significantly improved the growth performance and feed utilization in the treated groups over the control. Similarly, digestive enzyme activities were elevated in the intestines of treated groups. Moreover, feeding of supplemented diets containing AS13 significantly reduced the mortality rate caused by pathogenic Vibrio species (V. vulnificus, V. rotiferianus and V. campbellii). Our results indicated L. pentosus AS13 addition at 107 CFU g?1 can effectively enhance the growth performance, feed utilization, digestive enzymes and disease resistance of L. vannamei in the laboratory condition.  相似文献   

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