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1.
Abstract. Thirty-four A. hydrophila strains isolated from various fish species and several geographical locations in Malaysia were examined for their antibiotic resistance pattern and plasmid carriage. All strains were found to possess multiple resisitance, most commonly to ampicillin and carbenicillin. Six different antibiogroups representing 18 different antibiotic patterns were obtained. There were no differences in the resistance patterns of A. hydrophila isolates from healthy and diseased fish with ulcerative syndrome. Rifampicin was found to be the most active antibiotic against these strains. Isolation of plasmid DNA have a plasmid occurrence rate of only 14·7%. The molecular sizes of these plasmids ranged from 2·6 to 6Mda. Multiple carriage of plasmid is more likely with strains having three of four plasmids.  相似文献   

2.
Abstract. Eighty isolates of Aeromonas salmonicida , recovered from separate outbreaks of furunculosis in farmed and wild salmon in Scotland during 1988 and 1989, were examined for susceptibility to the β-lactam antibiotic amoxycillin. Susceptibility was determined in terms of minimum inhibitory concentration (MIC). All of the A. salmonicida subsp. salmonicida isolates investigated were susceptible to amoxycillin, with MICs of 0.30–1.50mg1-1. All of the A. salmonicida subsp. achromogenes isolates tested were resistant to amoxycillin, with MICs in excess of 500mgl-1. The A. salmonicida subsp. achromogenes produced a β-lactamase enzyme with a pI of approximately 8.0. The enzyme was inducible and its production was unaffected by plasmid curing with ethidium bromide, suggesting that resistance was chromosomal rather than plasmid mediated.  相似文献   

3.
Abstract. A collection of 130 strains of the bacterial fish pathogen Aeromonas salmonicida subsp. salmonicida isolated from diseased salmonids in Denmark, Norway, North America and Scotland has been characterized with regard to protein patterns, antibiotic resistance and exoprotease activity. Whole cell and outer membrane protein profiling could distinguish three different profiles in A. salmonicida. Eight outer membrane proteins were demonstrated (49, 40, 38, 37, 33, 31, 30 and 29 kDa). One protein profile was deficient in a 38 kDa outer membrane protein and instead contained an outer membrane protein of 37 kDa which was not detectable among the other protein profiles. Strains with the 37 kDa outer membrane protein showed multiple low-level antibiotic resistance towards cephalothin, penicillin, chloramp-henicol, tetracycline and quinolones. In addition, these strains were exoprotease deficient. Strains with the 37 kDa protein were unable to degrade cattle and trout serum proteins and displayed a delayed degradation of casein. Haemolysis on cattle blood agar plates was similarly delayed. In vivo examination of extracellular products from a normal protein profile strain and one with the 37 kDa outer membrane protein demonstrated major differences in pathological effects in rainbow trout. The strain possessing the 37 kDa outer membrane protein produced almost no pathological effects while the normal protein profile strain produced typical furuncles.  相似文献   

4.
Twelve strains of fish pathogenic aeromonads were identified by 16S rRNA sequencing as Aeromonas bestiarum , A. hydrophila , A. hydrophila subsp. dhakensis , A. salmonicida subsp. salmonicida , A. sobria biovar sobria and A. veronii biovar sobria. Following intramuscular injection, A. hydrophila subsp. dhakensis caused dark liquefying, raised furuncle-like lesions in rainbow trout within 48 h. Extracellular products of all cultures contained gelatinase and lecithinase, and most revealed lipase. Congo red absorption and siderophore production was recorded, but not so the suicide phenomenon or slime production. Sodium dodecyl sulphate polyacrylamide gel electrophoresis profile of the outer membrane proteins (OMP) revealed 10–25 bands, of which major bands were seen in the region of 32.5–47.5 and 62–83 kDa. Marked heterogenicity of the OMP and whole cell protein (WCP) profiles within and among the species was observed. Polypeptides of 83–173 kDa were detected in the WCP profile of the cultures, but they were not expressed in OMP fractions.  相似文献   

5.
Aeromonas genomes were investigated by restriction digesting chromosomal DNA with the endonuclease Xba I, separation of restriction fragments by pulsed field gel electrophoresis (PFGE) and principal components analysis (PCA) of resulting separation patterns. A. salmonicida salmonicida were unique amongst the isolates investigated. Separation profiles of these isolates were similar and all characterised by a distinct absence of bands in the 250kb region. Principal components analysis represented these strains as a clearly defined homogeneous group separated by insignificant Euclidian distances. However, A. salmonicida achromogenes isolates in common with those of A. hydrophila and A. sobria were shown by principal components analysis to be more heterogeneous in nature. Fragments from these isolates were more uniform in size distribution but as demonstrated by the Euclidian distances attained through PCA potentially characteristic of each strain. Furthermore passaging of Aeromonas isolates through an appropriate host did not greatly modify fragment separation profiles, indicative of the genomic stability of test aeromonads and the potential of restriction digesting/PFGE/PCA in Aeromonas typing.  相似文献   

6.
Abstract. A bacterium resembling Aeromonas salmonicida and determined to be the aetiologic agent of a cutaneous ulcerative disease in goldfish Carassius auratus (L.) was further characterized in this study.
Forty-five isolates of the bacterium (43 from the United States and one each position (moles % guanine plus cytosine) and DNA homology. The bacteriological atypical A. salmonicida previously described. Several important biochemical characteristics distinguished the goldfish isolates from typical A. salmanicida , but the DNA binding experiments indicated a high degree of relatedness between the goldfish isolates and typical A. salmonicida strains.  相似文献   

7.
During a 2-year period, bacterial fish pathogens were monitored on five rainbow trout, Oncorhynchus mykiss (Walbaum), freshwater farms in Denmark. A total of 1206 fish were examined and 361 bacterial isolates were identified phenotypically. Enteric redmouth disease, furunculosis and rainbow trout fry syndrome/coldwater disease were recorded. Infections caused by Flavobacterium psychrophilum occurred most frequently, but only one outbreak of enteric redmouth disease caused by Yersinia ruckeri serotype O1 and one of furunculosis caused by Aeromonas salmonicida were recorded during the monitoring period. Flavobacterium psychrophilum was isolated on all farms, both during disease outbreaks and from fish without any signs of disease. Serological investigations of F. psychrophilum showed that serotype Th was the dominant serotype found. The serotypes Th and Fd were involved in disease outbreaks of fry and larger fish. All isolates of F. psychrophilum showed proteolytic activities; however, a few isolates, belonging to serotype FpT did not degrade elastin and were not associated with mortality. Increasing resistance problems to oxytetracycline were demonstrated. More than half of the F. psychrophilum isolates showed resistance to oxolinic acid and oxytetracycline. No antibiotic resistant isolates were found among Y. ruckeri and A. salmonicida .  相似文献   

8.
Abstract. A bath challenge system was used to infect carp. Cyprinus carpio L., with Aeromonas salmonicida subsp. nova , the causative agent of carp cruthrodermatitis. Bath-challenged fish became infected with the bacterium exihibitinng typical signs of the disease, Carp that were sublethally bath exposed became infected and exhibited some skin lesions, but after one week, these quickly healed and the animals fully recovered from the infection, Naive fish that had not been previously exposed to the bacterium had mortalities of 100% when infected by the subcutaneous route and 40–60% by the bath route of infection. Carp that received sublethal infections were able to withstand subsequent lethal infection and recover regardless of the route of infection. Sublethally bath-exposed carp were protected from subsequently lethal challenges of A. salmonicida subsp. nova for at least 5 months.  相似文献   

9.
Abstract. The spread of goldfish ulcer disease (GUD) from Victoria to New South Wales, Australia, and the first isolation of Aeromonas salmonicida from wild goldfish are reported. Cultural, biochemical and protein SDS-PAGE characteristics of these recent isolates are compared with those of existing Australian isolates, with strains recovered from goldfish in Italy and the USA (atypical strains) and with strain ATCC 14174 (typical strain). The Australian isolates were identical and closely resembled the exotic atypical strains. Although there were several biochemical differences between the atypical isolates and the typical ATCC 14174 strain, the results of SDS-PAGE confirmed that these strains were closely related. The homology of the Australian and overseas strains recovered from goldfish supports the common view that A. salmonicida was introduced first into Australia with diseased goldfish in 1974. The three widely separated outbreaks of GUD reported here confirm that an atypical strain of A. salmonicida is now endemic in Australia.  相似文献   

10.
为探明斑点叉尾[鱼回](Ictalunes punctatus)溃烂症的病因,从4尾患鱼肝脾中分离纯化出4株优势菌株,并进行病原鉴定、毒力基因检测、动物回归感染和药敏试验。4株优势菌经鉴定并命名为杀鲑气单胞菌无色亚种(Aeromonas salmonicida subsp achromogenes)X-G1,杀鲑气单胞菌杀鲑亚种(A.s subsp salmonicida)X-P2、X-P3和嗜水气单胞菌(A.hydrophila)X-P4。15℃时,杀鲑气单胞菌X-G1、X-P2和X-P3的世代时间(约14 min)均小于嗜水气单胞菌X-P4(约20 min);25℃时,杀鲑气单胞菌X-G1、X-P2和X-P3株的世代时间(约20 min)均大于嗜水气单胞菌X-P4株(约16 min)。X-G1株可检到弹性蛋白酶、溶血素和甘油磷脂胆固醇酰基转移酶等3种毒力基因;X-P2株仅可检到弹性蛋白酶1种毒力基因;X-P3株可检测到弹性蛋白酶、溶血素、细胞毒性肠毒素、丝氨酸蛋白酶、酯酶、气溶素和甘油磷脂胆固醇酰基转移酶等7种毒力基因;X-P4株可检测到鞭毛、弹性蛋白酶、气溶素、细胞毒性肠毒素、热不稳定性肠毒素、丝氨酸蛋白酶和溶血素等7种毒力基因。分离株X-G1、X-P2、X-P3和X-P4在15~17℃水温下腹腔注射攻毒的半数致死浓度(LD 50)依次为0.49×10^4、0.78×10^4、0.53×10^4、3.84×10^4 CFU/g;而在23~26℃水温下测得的LD 50依次为1.48×10^4、1.80×10^4、0.82×10^4、0.68×10^4 CFU/g。分离株混合感染比单一株感染均表现出更强的致死能力。分离菌株对多西环素、恩诺沙星、氟苯尼考均敏感,但因患病鱼不能摄食药饵而导致治疗失败。  相似文献   

11.
Streptococcus dysgalactiae strains have been isolated from cultured amberjack Seriola dumerili and yellowtail Seriola quinqueradiata in Japan. To characterize the fish isolates, we performed genetic analysis and compared the biochemical properties of these isolates with those of the S. dysgalactiae subsp. dysgalactiae and S. dysgalactiae subsp. equisimilis strains isolated from mammals. The genetic analysis revealed that the fish isolates were genetically very similar to each other with high DNA–DNA relatedness (>95.4%) and sequence homology. Meanwhile, the DNA relatedness between mammalian isolates and the fish isolates was 73.4–82.6%. In biased sinusoidal gel electrophoresis (BSFGE) analysis, the restriction patterns of mammalian isolates were different from those of fish isolates. The fish isolates did not show streptokinase activity in plasminogen obtained from mammals. These characteristics enabled us to distinguish between the fish isolates and the Sdd and Sde strains isolated from mammals. In order to obtain epidemiological information on the fish isolates, BSFGE patterns from 284 S. dysgalactiae strains from fish in Japan were examined. Based on the results of BSFGE analysis, the fish isolates were classified into 16 groups (AP1–AP16) with restriction enzyme ApaI. The dendrogram based on BSFGE analysis indicated that all fish isolates using in this study were closely related.  相似文献   

12.
In this study, exotoxins produced by 62 Aeromonas salmonicida strains and the bacterium Haemophilus piscium were analysed. Enzymatic assays, zymograms and serological detection were used to monitor secretion by bacterial strains of the previously described exotoxins P1, GCAT and AsaP1 and also the extracellular P2 metallo-gelatinase and a serine caseinase, which is different from the P1 protease and has not yet been characterized. Based on the results, the strains were divided into five groups. One comprised the type strains for A. salmonicida ssp. masoucida, H. piscium and 36% of the atypical isolates, and another, a type strain for A. salmonicida ssp. smithia together with 14% of the atypical isolates. A second type strain of A. salmonicida ssp. smithia was grouped with 8% of the atypical isolates. The largest group contained the type strains for A. salmonicida ssp. achromogenes and 38% of the atypical isolates. The type strains for A. salmonicida ssp. salmonicida were in the last group with all the four typical strains and 4% of the atypical isolates. The combination of zymogram and serological detection used is recommended as the most reliable method for characterizing A. salmonicida strains according to their exotoxin secretion.  相似文献   

13.
Abstract. Incubation temperatures of 11°, 18° and 28° did not substantially affect biochemical reactions of either virulent or avirulent forms of Aeromonas salmonicida subspecies salmonicida. The only change observed, amygdalin fermentation, was positive at 11° and 18° but negative at 28°C. Several isolates utilized sucrose, a characteristic not normally recognized for A. salmonicida subspecies salmonicida. Antimicrobial susceptibility screening indicated resistance to novobiocin increased at the higher incubation temperatures. Standardized drug sensitivity testing procedures and precise zone diameter interpretive standards for bacterial fish pathogens are needed.  相似文献   

14.
为探究嗜水气单胞菌中内生质粒与菌株对喹诺酮类抗生素耐药表型的关系,实验克隆并分析了分离自湖北仙桃某渔场患病团头鲂的对喹诺酮类抗生素耐药的嗜水气单胞菌W39菌株中的质粒pAhW39。测序结果显示,质粒pAhW39的大小为6 739 bp,GC含量为46.13%,低于目前已公布的嗜水气单胞菌染色体DNA的GC含量(60.1%～62.0%),表明该质粒可能是通过水平转移而获得;含有4个预测的开放阅读框(ORF),即nspV、nspV-like、repB和qnrS2,分别负责编码Ⅱ型核酸内切酶NspV和NspV-like、复制蛋白RepB和喹诺酮类耐药蛋白QnrS2。在无抗生素压力条件下,质粒pAhW39的稳定性较高,不容易丢失。通过微量肉汤稀释法检测菌株耐药性发现,与质粒pAhW39消失株(W39-C)相比,喹诺酮类的萘啶酸和环丙沙星对W39菌株的最小抑菌浓度分别升高16倍和8倍,表明载有qnrS2的pAhW39介导了W39菌株对喹诺酮类药物的耐药表型。比较基因组分析发现,pAhW39与分离自美国马里兰州某医院管道废水的气单胞菌ASNIH2菌株中的质粒pAER-e58e相似度极高,碱基一致性高达99.9%,表明pAhW39(或pAERe58e)传播具有广泛性和稳定性,同时提醒我们质粒介导的喹诺酮类抗生素耐药在鱼源气单胞菌中的存在,可能会导致喹诺酮类抗生素耐药表型在水产养殖上快速而广泛地传播。  相似文献   

15.
The health status of eight marine rainbow trout farms was followed from mid-June to mid-September 2006 by sampling both dead and healthy fish approximately every 2 weeks for bacteriological and virological investigation. No fish pathogenic viruses were detected, but all farms experienced disease and mortality as a result of various bacterial infections. Yersinia ruckeri was found on four and Renibacterium salmoninarum on five of the farms, but only during the first part of the surveillance period. This indicates that the fish carried the infection from fresh water, and cleared the infection in salt water. Aeromonas salmonicida subsp. salmonicida caused mortality on five farms, but persisted throughout the sampling period. Although A. salmonicida was probably carried from fresh water, the fish were not able to clear the infection in the sea. Vibrio anguillarum caused mortality on six of the farms throughout the sampling period, O1 being the dominant serovar, and Photobacterium damselae subsp. damselae was found on seven farms as a cause of disease. During the period of highest water temperatures Vibrio parahaemolyticus and Vibrio vulnificus were detected in dead fish in five and two farms, respectively, although their significance as causative pathogens is questionable. Vibrio vulnificus has not previously been found in rainbow trout in Denmark. Both mortality and number of antimicrobial treatments during the period were considerably higher in unvaccinated compared with vaccinated fish. Resistance to commonly used antimicrobials was low or absent.  相似文献   

16.
A Lancefield serological group C Streptococcus sp. was isolated from cultured amberjack, Seriola dumerili Risso, and yellowtail, Seriola quinqueradiata Temminck and Schlegel, immunized with Lactococcus garvieae commercial vaccines in Japan. The isolated bacteria were Gram-positive cocci, auto-aggregating in saline, morphologically long chains in growth medium, catalase negative and alpha-haemolytic on blood agar. An almost complete gene sequence of the 16S rDNA of two isolates was determined and compared with that of bacterial strains in the database. The isolates were identified as Streptococcus dysgalactiae based on the results of the 16S rDNA sequence, the bacteriological properties and the Lancefield serological grouping. Oligonucleotide primers specifically designed for the 16S-23S rDNA intergenic spacer region of S. dysgalactiae amplified a gene from all the fish isolates, as well as the type strains alpha-haemolytic S. dysgalactiae subsp. dysgalactiae ATCC430738 and beta-haemolytic S. dysgalactiae subsp. equisimilis ATCC35666, but not those of S. equi ATCC33398, Lactococcus garvieae ATCC43921 and L. garvieae KG9408. The severe necrotic lesions of the caudal peduncle seen in experimentally infected fish were similar to those seen in naturally infected fish.  相似文献   

17.
Abstract The abundances of Aeromonas salmonicida subsp. salmonicida in the water and in the surface microlayer was studied during the initial phase of a cohabitant infection experiment with Atlantic salmon, Salmo salar L., smolt. Aeromonas salmonicida was detected in the water samples only until the intraperitoneally infected smolt were dead and had been removed. In the lipid rich surface microlayer, A. salmonicida was detected in high concentrations from the day of the first fish mortality and throughout the rest of the experiment. The significance of the high cell surface hydrophobicity is discussed as a possible reason for enrichment of A. salmonicida at the air-water interface.  相似文献   

18.
A total of 23 Portuguese strains of Yersinia ruckeri , the causative agent of enteric redmouth disease (ERM), were comparatively studied by means of lipopolysaccharide (LPS) and outer membrane protein (OMP) analysis, plasmid profiling and ribotyping in order to investigate the heterogeneity among isolates and the usefulness of these methods as epidemiological markers. Only two LPS profiles were observed among the isolates studied, corresponding with the serotypes O1 and O3 of Y. ruckeri . A higher heterogeneity was detected analysing the OMP, seven different patterns being observed. Although some isolates carried different small plasmids, all the serotype O1 isolates showed a plasmid band of 50 MDa and all the serotype O3 strains shared in common a extrachromosomic DNA band of 30 MDa. The analysis of the ribopatterns obtained using three different enzymes, separated the strains into 10 ribotypes, indicating genetic heterogeneity among the isolates. The heterogeneity was greater within serotype O1 isolates, six ribotypes being detected, than within serotype O3 in which only three ribotypes were found. Although OMP analysis and ribotyping can be useful for the differentiation of strains on the basis of farm and/or season of isolation, we consider that ribotyping is the best candidate for epidemiological studies because it is easier to perform and offers a slightly better discriminative power.  相似文献   

19.
Aeromonas isolates were collected from cultured fish, characterized phenotypically and identified to species using 16S rDNA. The pathogenicity of all isolates was assayed on the basis of haemolytic and proteolytic activity and challenge tests were performed for isolates from healthy fish. A total of 131 Aeromonas isolates were obtained and identified as follows: A. hydrophila (13), A. bestiarum (23), A. salmonicida (motile biogroup) (19), A. caviae (2), A. sobria (18), A. veronii bt. sobria (42), A. jandaei (1), A. encheleia (11) and A. allosaccharophila (2). All isolates of A. hydrophila and A. bestiarum and most isolates of A. salmonicida and A. veronii were classified as pathogenic. Aeromonas hydrophila was isolated only from diseased trout except for one isolate obtained from carp fry. The other potentially pathogenic Aeromonas species were present in diseased as well as healthy fish. The pathogenicity of isolates from healthy fish was correlated with their enzymatic activity and was also tested by challenge experiments. The dominant pathogenic species were A. veronii bt. sobria, A. bestiarum and A. salmonicida in common carp and A. hydrophila in rainbow trout.  相似文献   

20.
Abstract. The infectivity of the bacterial fish pathogen Aeromonas salmonicida subsp. salmonicida to Atlantic salmon, Salmo salar L., in sea water was investigated and found to be similar to that reported for fresh water. The minimal infective dose in short duration bath exposures (1–3 days) was 104 colony-forming units (cfu) per ml, while prolonged exposure for three weeks, but not for 1 week, produced infection with 102 cfu/ml. Intragastric intubation of A. salmonicida established infection with doses of >105 cfu. Release of bacteria from dead or morbid infected fish was monitored and found to be in the order of 105–108 cfu/fish/h. These results emphasize the importance of removing dead fish from farm sites.  相似文献   

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