Direct detection of Yersinia pestis from the infected animal specimens by a fiber optic biosensor

The FOB-3, anew type fiber optic biosensor, is designed to rapidly detect a variety of biological agents or analytes with better stability, sensitivity and specificity. In order to detect Y. Pestis, a sandwich immunoassay was developed by using the purified antibody against antigen FI immobilized on polystyrene probes as the capture antibody and the monoclonal antibody-Cy5 conjugate as the detector. After a series of optimization for the stability, sensitivity and specificity of the FOB-3, 50-1000 ng/ml of antigen FI and 6 x 10(1)-6 x 10(7) CFU/ml Y. pestis could be detected constantly in about 20 min, and Y pestis could be detected specifically from Y. pseudotuberculosis, Y. enterocolitica, B. anthracis and E. coli. Then, 39 blind samples, including 27 tissues of mice infected with Y pestis and 12 tissues of healthy mice as negative control, were detected with the FOB-3. 92.6% infected tissues were identified from the tissues of healthy mice and the tissues containing more than 100 CFU/ml bacteria could be detected by the biosensor. The results demonstrated the feasibility of the FOB-3 as an effective method to detect Y. pestis rapidly and directly from the infected animal specimens with the advantage of portability, simple-operation as well as high sensitivity and specificity. (c) 2006 Elsevier B.V. All rights reserved.

Rapid quantitative detection of Yersinia pestis by lateral-flow immunoassay and up-converting phosphor technology-based biosensor

Up-converting phosphor technology (UPT)-based lateral-flow immunoassay has been developed for quantitative detection of Yersinia pestis rapidly and specifically. In this assay, 400 nm up-converting phosphor particles were used as the reporter. A sandwich immumoassay was employed by using a polyclonal antibody against F1 antigen of Y. pestis immobilized on the nitrocellulose membrane and the same antibody conjugated to the UPT particles. The signal detection of the strips was performed by the UPT-based biosensor that could provide a 980 nm IR laser to excite the phosphor particles, then collect the visible luminescence emitted by the UPT particles and finally convert it to the voltage as a signal. V-T and V-c stand for the multiplied voltage units for the test and the control line, respectively, and the ratio V-T/V-C is directly proportional to the number of Y pestis in a sample. We observed a good linearity between the ratio and log CFU/ml of Y pestis above the detection limit, which was approximately 10(4) CFU/mI. The precision of the intra- and inter-assay was below 15% (coefficient of variation, CV). Cross-reactivity with related Gram-negative enteric bacteria was not found. The UPT-LF immunoassay system presented here takes less than 30 min to perform from the sample treatment to the data analysis. The current paper includes only preliminary data concerning the biomedical aspects of the assay, but is more concentrated on the technical details of establishing a rapid manual assay using a state-of-the-art label chemistry. (c) 2006 Elsevier B.V. All rights reserved.

鲢、鳙鱼一种新的传染病——Yersinia ruckeri,一种新的鲢、鳙鱼病原菌

<正> 历来以少病易养、产量高著称的鲢、鳙鱼近年来却爆发了一种新的流行病,而且流行面很广,从南方各省至京津地区均有发生。罹病鱼一周之内便会出现大批死亡,甚至可以死光。 据我们观察该鱼病以体表发炎充血为特征,特别在体表两侧,以及腹鳍下和尾柄处、眼眶、鳃盖、头、嘴等部位出现,但每条病鱼症状并不完全相同。有的还可见突眼和鳃丝贫血。内部

Effects of the “all-fish” GH (growth hormone) transgene expression on resistance to Ichthyophthirius multifiliis infections in common carp, Cyprinus carpio L.

A study was undertaken on the susceptibility of the F-4 generation of "all-fish" growth hormone transgenic carp, Cyprinus carpio L, against Ichthyophthirius multifiliis infections. When 1-year old, transgenic carp, with non-transgenic carp and non-manipulated carp (controls) were split into three batches, and experimental infections were performed throughout the 3-month period. All 72 fish were successfully infected. It was shown that there was a significant difference (P<0.01) on infection level between transgenics and non-transgenics, and transgenics and controls. It possibly resulted from transgenics that had stronger non-specific immune functions. In addition, fish surface area affected significantly infection level (P<0.001). Carp with larger surface area harboured more parasites for each type of fish, but transgenic with larger surface area than non-transgenics and controls (P<0.01), loaded fewer parasites than others. Besides, the time of infection also greatly influenced (P<0.001) infection level. Results showed that there was a significant decline in parasite infectivity through October to November (P<0.001). It was likely to suggest that there existed senescence resulted in failure of any I. multifiliis isolate maintenance. Significant difference in infectivity between isolate G from grass carp and isolate H from gold fish suggested that different parasite strains may exist. (C) 2009 Elsevier B.V. All rights reserved.

High-throughput synergy screening identifies microbial metabolites as combination agents for the treatment of fungal infections

The high mortality rate of immunocompromised patients with fungal infections and the limited availability of highly efficacious and safe agents demand the development of new antifungal therapeutics. To rapidly discover such agents, we developed a high-throughput synergy screening (HTSS) strategy for novel microbial natural products. Specifically, a microbial natural product library was screened for hits that synergize the effect of a low dosage of ketoconazole (KTC) that alone shows little detectable fungicidal activity. Through screening of approximate to 20,000 microbial extracts, 12 hits were identified with broadspectrum antifungal activity. Seven of them showed little cytotoxicity against human hepatoma cells. Fractionation of the active extracts revealed beauvericin (BEA) as the most potent component, because it dramatically synergized KTC activity against diverse fungal pathogens by a checkerboard assay. Significantly, in our immunocompromised mouse model, combinations of BEA (0.5 mg/kg) and KTC (0.5 mg/kg) prolonged survival of the host infected with Candida parapsilosis and reduced fungal colony counts in animal organs including kidneys, lungs, and brains. Such an effect was not achieved even with the high dose of 50 mg/kg KTC. These data support synergism between BEA and KTC and thereby a prospective strategy for antifungal therapy.

Host sex and ectoparasite infections of plateau pika (Ochotona curzoniae, Hodgson) on the Qinghai-Tibetan Plateau

A total of 449 plateau pika (Ochotona curzoniae Hudgson) individuals were sampled with rattraps from 21 plots (size 1 ha) randomly scattered over the area of the species distribution at the altitude 3275-4807 in a.s.l. in the Qinghai-Tibetan Plateau (West China). Two main ectoparasite species Hypoderma satyrus Brauer and Ixodes crenulatus Neumann of plateau pika were surveyed, and the relations between host sex and parasitism were analyzed. The results were: (i) although not significantly, the infection rate of female young was close to zero and lower than that of male young (6%), while the infection rate of female sub-adults (19%) was contrarily - higher than that of male sub-adults (11%); adult females had significantly higher (41%) infection rate than that of males (18%) (P<0.001); (ii) the parasite infection rates for both males and females increased with increasing age, but female age-groups had obviously steeper slope. We suggested that the differences of body mass, growth rate and home range between males and females had mainly caused the sex-biased parasitism (SBP) of plateau pika at each age stage. Also, due to the higher increases of body mass and maybe as well as of the home range differences between consecutive age-groups, the parasite infections of females became more sensitive to the influences of age than that of males.