The incidence of allotypes of the genes of the fourth component (C4) and factor B of the complement system was compared in 252 persons under 45 years of age ("young" group) with 482 people between 61 and 90 years of age ("old" group). One hundred people older than 90 years of age (nonagenarians) were also investigated. A striking difference was found between the "young" and "old" groups in the incidence (16.1% and 5.4%, respectively) of a silent gene of the C4B allele (C4B*Q0). This difference was even more marked among "young" and "old" men (17.6% vs 3.4%). The incidence of the C4B*Q0 allele in women dropped to the level of the men only in the nonagenarian group. The most probable explanation for this finding is that people carrying the C4B*Q0 allele die from as yet unidentified disease(s) in their middle-age. Therefore, male (and to a lesser extent female) carriers of this allele may have a considerably shorter life expectancy than individuals without a silent gene in the C4B locus.
The bacterium Flavobacterium columnare was recovered and identified as the aetiological agent causing freshwater columnaris infection in farmed striped catfish Pangasianodon hypophthalmus (Sauvage) fingerlings that had suffered high mortality rates within commercial hatchery ponds in Vietnam. The gross clinical signs were typical of columnaris-infected fish. Histological examination found numerous Gram-negative, filamentous bacteria present on the skin, muscle and gill tissues of affected fish. The yellow-pigmented bacteria were isolated and identified as F. columnare using primary, biochemical and PCR methods. An experimental immersionchallenge study with 2 strains was also performed. It fulfilled Koch's postulates and showed a median lethal concentration (LC 50 ) of 4.27 × 10 5 and 1.66 × 10 6 cfu ml −1 for the F. columnare strains FC-HN and FC-CT, respectively. To the best of our knowledge this is the first report of freshwater columnaris infection in P. hypophthalmus. KEY WORDS: Flavobacterium columnare · White patch disease · Pangasianodon hypophthalmus Resale or republication not permitted without written consent of the publisherDis Aquat Org 100: [83][84][85][86][87][88] 2012 with similar signs to those described for columnaris infections in other fish species. Outbreaks of F. colum nare in P. hypophthalmus have not yet been reported from Vietnam or elsewhere, and so the aim of the present study was to investigate the disease and identify the aetiological agent associated with the high fingerling mortalities in Vietnamese P. hypo phthalmus hatcheries. An experimental bacterial challenge study was also completed to confirm Koch's postulates and to determine the median lethal concentration (LC 50 ) for 2 different F. columnare strains on P. hypophthalmus. MATERIALS AND METHODSA total of 83 Pangasianodon hypophthalmus (weighing 3 to 20 g) were collected during natural disease outbreaks from 5 hatchery and 7 earthen pond farms located in Vietnam. Histology samples of the skin, gill, kidney, liver and spleen were aseptically removed, placed in 10% (v/v) neutral buffered formalin and processed for routine wax sections. Four-micron thick sections were cut and stained with haematoxylin and eosin (H&E) and Giemsa (Roberts 1989). These were examined under light microscopy. Bacterial isolation was performed where samples were taken aseptically from gills, skin, liver, kidney and spleen of the affected animals directly onto peptone, yeast extract, salt and agar (PYES) (Triyanto & Wakabayashi 1999) and tryptone soy agar (TSA; Oxoid) and then incubated at 28°C. Inoculated agar plates were checked daily up to 4 d post-inoculation for the presence of yellow-pigmented colonies, and primary identification tests included Gram stain, oxidase, oxidation/fermentation (O/F) of glucose, and motility, as described in Frerichs & Millar (1993). Biochemical tests on the yellow-pigmented bacteria (YPB) included catalase, temperature tolerance (13, 15 and 36°C), NaCl tolerance (0.5 and 1%), citrate utilisation, productio...
22Eight tetracycline resistant Edwardsiella ictaluri isolates obtained from diseased freshwater catfish 23 (Pangasianodon hypophthalmus) in Vietnam, and showing different resistance phenotypes to other 24 antimicrobial agents, were studied. The tet genes were determined using PCR. Conjugation 25 experiments were performed to assess transferability of the tetracycline resistance determinant and the 26 size and incompatibility group (Inc) of each tet-carrying plasmid were determined. PCR and 27 sequencing were used for characterization of the co-transferred resistance genes. A tetA gene was 28 demonstrated in the E. ictaluri isolates and for all of them, E. coli transconjugants were obtained. All 29 transconjugants contained high-molecular weight tetA-carrying plasmids (~140 kb) belonging to the 30 incK group, as was shown with the PCR-based replicon typing method. The strA-strB, dhfr1 and sul 2 31 genes were detected on the tetA-carrying plasmids of the transconjugants showing resistance to 32 streptomycin, trimethoprim and sulfonamides, respectively. The dhfr1 gene was found to be located in 33 a class 1 integron as determined by PCR and sequencing. Interestingly, the 3' CS region of class 1 34 integrons was not detected by PCR. This study shows the presence of incK plasmid-mediated 35 tetracycline resistance among E. ictaluri isolates from diseased freshwater catfish in Vietnam. 36 37 3
While preformed BSA-anti-BSA immune complexes (PIC) bind efficiently to human RBC after their interaction with human complement, nascent BSA-anti-BSA immune complexes (NIC) formed in the presence of complement do not bind to autologous RBC. The same results were obtained with tetanus toxoid-anti-tetanus toxoid PIC and NIC. In order to elucidate the causes of this marked difference between the RBC-binding properties of PIC and NIC, the profile of complement activation induced by them was compared using haemolytic assays and sensitive ELISA tests. BSA-anti-BSA NIC activated Cl more efficiently than PIC. This was reflected in a higher C4 content of the isolated NIC and higher Cl INH-Cls and lower Clq-fibronectin complex level in the NIC-treated serum as compared to the PIC-treated ones. Although isolated NIC contained more C3 than isolated PIC did, there was no significant difference in the AP activation. These findings suggest that the failure of NIC to bind to RBC is not due to a lack of C4-binding, or C3-binding and/or activation, but rather to the special structure of this type of complex.
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