鱼类肠道微生物总DNA的提取

尝试提取鲫(Carassius auratus)肠道菌群总DNA,为研究鱼类肠道菌群结构提供依据。以鲫肠道内容物为样本,用PBS多次洗涤,离心样品,沉淀菌体。使用试剂盒法提取肠道菌群总DNA,电泳结果显示,样品DNA条带明亮,无降解现象,可用于后续分子生物学试验研究;通过设计的细菌通用引物,对其16S rDNA基因进行PCR扩增,得到较清晰的图谱,条带整齐;表明采用该方法提取鱼类肠道微生物群落的DNA较为简单、准确、可行。     

Francisella sp., an emerging pathogen of tilapia, Oreochromis niloticus (L.), in Costa Rica

Francisella sp. is an emergent bacterial pathogen that causes acute to chronic disease in warm and cold water cultured and wild fish species. During the past 3 years, the bacterium has been detected in tilapia, Oreochromis niloticus , cultured in Costa Rica. Infected fish presented non-specific clinical signs, such as erratic swimming, anorexia, anaemia, exophthalmia and high mortality. Upon macroscopic and microscopic examination, several internal organs (mainly spleen and kidney) were enlarged and contained white nodules. Histological examination revealed the presence of multifocal granulomatous lesions, with the presence of numerous small, pleomorphic, cocco-bacilli. The bacteria were isolated from infected tilapia on selective media and grown on several media with and without antibiotics. Specific PCR primers to the Francisella genus were used to confirm the preliminary diagnoses. In comparison with several bacterial 16S rRNA sequences, our isolate was found to share 99% identity with other Fransicella spp. isolated from fish, and more than 97% identity to the human pathogen Francisella tularensis . Koch's postulates were fulfilled after experimental intraperitoneal and gill exposure challenges.     

The prevalence of mycobacterial infections in striped bass in Chesapeake Bay

Several species of bacteria have been isolated from diseased striped bass, Morone saxatilis (Walbaum), in Chesapeake Bay. Mycobacteria species are of particular interest because of their association with chronic lesions in both fish and humans. The resulting disease in fish may be characterised by emaciation, inflammation of the skin, exophthalmia (pop‐eye), ascites (dropsy), open lesions, and ulceration. The prevalence of mycobacterial infection in 217 striped bass in the Maryland portion of Chesapeake Bay was determined to provide evidence of decreased overall condition of fish affected by these bacteria. The density of the granulomas was higher in the spleen and head kidney than either the heart or liver, and appeared to be most closely associated with the presence of an external lesion. Thirty‐eight per cent of the fish showed some sign of an external lesion. Granulomas appeared in at least one organ in 53% of the fish sampled regardless of the presence or absence of an external skin lesion. Condition factor was significantly higher for striped bass without external lesions (0.96) than those with lesions (0.82). Striped bass with no internal granulomas and no external lesion had the highest condition factor (0.99) and fish with granulomas and external lesions the lowest (0.81). Slopes of the regression log_e weight (g) and log_e length (mm) for striped bass with external lesions was significantly higher than those fish without external lesions and had a lower r². The results suggest that striped bass that are infected with mycobacteria have decreased overall health.     

一株南极大磷虾共附生细菌的分离鉴定及一氧化氮靶向抑制活性筛选

从我国南极磷虾科学探捕项目所采集的南极大磷虾(Euphausia superba)样品中分离纯化到一株共附生细菌,对其进行了细菌多相分类学分析、发酵培养、代谢产物提取及HPLC分析,并对其发酵粗提物进行了针对多种重大疾病药物靶标一氧化氮(N0)抑制活性的靶向筛选.结果表明,该菌株与其进化关系最近的需盐杆菌(Salege...     

Morphopathological features of a severe ulcerative disease outbreak associated with Tenacibaculum maritimum in cultivated sole, Solea senegalensis (L.)

This study describes morphopathologic changes in naturally infected farmed Senegalese sole affected by tenacibaculosis caused by Tenacibaculum maritimum. Macroscopic observation, in addition to light microscopy and scanning electron microscopy, was used to study the lesions. Main lesions were characterized by complete loss of epidermis and dermis, as well as extensive necrosis of muscle layers. Mild-to-moderate inflammatory response with the presence of macrophages was noted around hyaline degenerated muscle cells. Gram-negative filamentous bacteria could be detected only at the dermis. Under scanning electron microscopy, filamentous bacteria located over the scales without epithelium could be observed. These findings together with the isolation and PCR detection of the bacteria in kidney and skin tissues suggest that once the bacteria reach the dermis, probably through eroded epidermis, they are able to proliferate and produce enzymes that are responsible for the damage in the underlying tissues.     

Oomycete fungi associated with ulcerative mycosis in menhaden, Brevoortia tyrannus (Latrobe)

Abstract. Deep necrotic ulcers in Atlantic menhaden, Brevoortia tyrannus (Latrobe), were consistently associated with the presence of oomycete fungi. These organisms were found in over 95% of all lesions both early and late. More than one species of fungus appears to be involved, indicating that these organisms are secondary to some other stressor. However, all characteristically elicit an atypical intense granulomatous inflammatory response and do not behave pathologically as typical oomycetes. Our observation that these fungi appear to be the only organisms consistently present in the earliest stages of the disease indicates that some non-infectious stressor may be responsible for initiating the lesions and subsequently allowing the fungi to induce this atypical response.     

Cephalic osteochondritis and necrotic scleritis in intensively reared salmonids associated with Flexibacter psychrophilus

Three cases of pyogranulomatous cephalic osteochrondritis of intensively reared rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., in Canada and Chile, respectively, were examined for histopathological and bacteriological changes, and by using immunohistochemistry. Bilateral exophthalmia and intraocular haemorrhage were the most common gross lesions seen in the Ontario fish. Histologically, the major pathological changes seen in all cases involved the developing bone and cartilage of the head region, including the eye. Necrosis and pyogranulomatous inflammation of the scleral cartilage (necrotic scleritis) were the major ocular changes. Similarly, lysis of cephalic cartilage and immature bone, accompanied by pyogranulomatous inflammation, usually progressing to fibrosis, were the most common lesions associated with the cranial changes in both the rainbow trout and Atlantic salmon. Routine histological staining, including special stains, failed to reveal the presence of pathogens associated with these lesions. However, immunohistochemical staining of representative sections from all cases with rabbit anti- Flexibacter psychrophilus serum (ATCC 49510) demonstrated significant numbers of antigenically related bacteria within the leading edge of some of the scleral and cephalic osteochondritic lesions. Axenic cultures of Flexibacter psychrophilus were recovered from the eye lesions of the rainbow trout, but it was not possible to reproduce ocular lesions experimentally. However, mortality was produced following intramuscular injection of rainbow trout with bacteria.     

Occurrence of Mycobacterium spp. in ornamental fish in Italy

The occurrence of Mycobacterium spp. in freshwater and marine ornamental fish was studied in Italy from June 2002 to May 2005. Two surveys were carried out, one of aquarium fish sent to the Laboratory for diagnosis, and the other of prevalence of infection by mycobacteria in ornamental fish imported into Italy. Bacterial isolation was carried out from the spleen, kidney and liver, and the isolates were subsequently identified by biochemical tests. In the first survey, 387 fish were examined and Mycobacterium spp. were isolated from 181 (46.8%) fish. In the second survey 127 batches of ornamental fish from different countries were examined. Mycobacterium spp. were isolated from 38 (29.9%) batches. The following species were found: M. fortuitum, M. peregrinum, M. chelonae, M. abscessus, M. marinum, M. gordonae, M. nonchromogenicum and M. interjectum. There was a high prevalence of infection independent of the presence of macroscopic lesions. Mycobacterium fortuitum and M. chelonae were more prevalent than M. marinum in the samples examined.     

Systemic nocardiosis in a Mediterranean population of cultured meagre,Argyrosomus regius Asso (Perciformes: Sciaenidae)

Marine cultured meagre, Argyrosomus regius Asso, in central and western Greece were affected by an outbreak of systemic granulomatous disease subsequently demonstrated to be nocardiosis. The fish were originally imported as juveniles from hatcheries in France and Italy and on‐grown in Greece, the latter also providing broodstock for a small number of local Greek hatcheries for the production of second‐generation juveniles. The disease in cage reared fish had been present throughout the year, particularly in the 1+ and 2+ year old fish with a low to variable morbidity and 1–4% total mortality. Multiple lesions were visible externally on the skin of affected fish, with severe ulcerations and necrosis. Internally, multifocal yellowish‐white nodules, 0.1–0.5 cm in diameter, were visible on the surface of several internal organs. Histopathology revealed systemic granulomatous inflammation. Fite‐Faraco staining clearly demonstrated the presence of Nocardia‐like organisms which were Gram‐positive, long, rod to beaded filamentous bacteria. Nocardia genus‐specific 16s RNA primers NG1 and NG2 were used to generate a 600 bp fragment recovered from affected tissue, confirming the diagnosis of Nocardia spp. To our knowledge, this is the first report of nocardiosis in meagre.     

Clinical and bacteriologic studies of the frequency of mastitis during and after parturition in heifers lactating for the first time

The udders of 100 heifers were examined for clinical changes during parturition. Of each quarter colostral samples were taken and analyzed bacteriologically. 35 heifers (13.5% of the quarters) showed clinical changes of the quarters and/or of colostral samples. 14 of these animals (4.75% of the quarters) suffered from cellulitis-like mastitis. 13 (5.25% of the quarters) had acute catarrhalic mastitis and eight heifers (3.5% of the quarters) showed acute galactophoritis. In all milk samples of animals with pathological changes of the udder or of colostrum the causing bacteria could be identified. Besides the group of 35 heifers with clinical lesions udder-pathogenic bacteria were found in samples of 24 apparently healthy animals (20.5% of the quarters) during parturition. However, these animals failed to show clinical signs of inflammation at least until the end of this study (10 days post partum). Isolated bacteria included facultative and obligate pathogenic species, 70% of which were gram-positive cocci (i.e. Streptococcus [Sc.] uberis, Sc. dysgalactiae, Sc. agalactiae, Staphylococcus aureus and other staphylococci) versus 30% of gram-negative bacteria (i.e. Escherichia [E.] coli, Klebsiella and other coliform species. In-vitro-susceptibility tests showed best effectiveness of Penicillin against Sc., Cloxacillin against staphylococci and Gentamycin and Polymyxin B against coliform bacteria. Possible pathways, leading to bacterial infection of first lactating heifers during parturition, are discussed. Pathways of infection seem to be of lesser importance for the development of apparent, sometimes severe mastitis with coliform bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)