Origins of ciguatera fish poisoning: a new dinoflagellate, Gambierdiscus toxicus Adachi and Fukuyo, definitively involved as a causal agent.
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Animals↗
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Results for “Causal Agent”
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THE NATURE OF THE CAUSAL AGENT OF WHITE LEAF DISEASE OF SUGARCANE.
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Plant Viruses↗
Potato spindle tuber disease produced by pathogenic RNA from citrus exocortis disease: evidence for the identity of the causal agents.
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Electrophoresis, Polyacrylamide Gel↗
Occupational asthma caused by eastern white cedar (Thuja occidentalis) with demonstration that plicatic acid is present in this wood dust and is the causal agent.
A worker developed symptoms of work-related asthma a few weeks after starting to work in a sawmill where eastern white cedar (Thuja occidentalis) was transformed into shingles. The diagnosis of occupational asthma was confirmed by monitoring of peak expiratory flow rates and bronchial responsiveness to histamine off work and at work, and specific inhalation challenges in the laboratory that demonstrated an isolated late asthmatic reaction after exposure for 4 hours to the wood dust. Specific inhalation challenges with western red cedar (thuja plicata) for 2 hours and plicatic acid (PA) for 7 minutes also caused an isolated late asthmatic reaction. Elevated specific IgE levels to PA were present. Antiserum was produced in rabbits that were immunized with PA conjugated to human serum albumin. With this antiserum in inhibition experiments, cross-reactivity between western red cedar and eastern white cedar, both belonging to the family of arborvitae, was found. It is estimated that eastern white cedar contains approximately half the amount of PA present in western red cedar.
Adult↗
Borna disease virus: possible causal agent in psychiatric and neurological disorders in two families.
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Adult↗
The causal agent of halo blight in bean, Pseudomonas syringae pv. phaseolicola, attaches to stomata via its pili.
The phytopathogenic pseudomonad Pseudomonas syringae pv. phaseolicola causes halo blight of bean (Phaseolus vulgaris L.). Initiation of infection depends on the ability of the cells to adhere to the target cell surface. P. syringae pv. phaseolicola expresses pili, which are the receptors of the lipid-containing dsRNA bacteriophage phi 6. phi 6-resistant bacterial strains can be divided into different piliation types. It was possible to show that the adhesion of the bacteria onto plant cell surface was dependent on the pili. Non-piliated bacterial stains showed a much lower adherence to the leaf surface than strains expressing phi 6 specific pili. Scanning electron microscopy showed that the piliated bacteria attached to the leaf surface at the site of stomata. Non-piliated bacteria were evenly distributed on the leaf surface. All bacterial strains used in this study were capable of causing halo blight if injected into the plant. If the bacteria were sprayed on the plants, followed by spraying of sterile buffer, only piliated bacteria caused symptoms.
Bacterial Adhesion↗
Identity of the causal agents of human babesiosis in Europe.
Most cases of human babesiosis are caused either by Babesia divergens in Europe or Babesia microti in America. B. microti, once regarded as a single species, occurs as a world-wide species complex and although both phenotypic and genotypic features lend support to suggestions that zoonotic B. microti may occur in Europe, convincing medical evidence is lacking. Several B. divergens-like parasites have emerged in the last few years, but 18S rRNA gene analysis suggests that B. divergens 'sensu stricto' is restricted to European (and North African) cattle. Some of the B. divergens-like parasites only differ from the bovine type by a few bases, and it remains to be determined whether this is sufficient to accord them separate species status. Comparative biology should support genetic data in taxonomic studies of both B. divergens and B. microti.
Animals↗
Purification and characterization of cassiicolin, the toxin produced by Corynespora cassiicola, causal agent of the leaf fall disease of rubber tree.
Cassiicolin, a phytotoxin produced by the necrotrophic fungus Corynespora cassiicola, was purified to homogeneity from a rubber tree isolate. The optimized protocol involves reverse phase chromatography followed by size exclusion chromatography, with monitoring of the toxicity on detached rubber tree leaves. Cassiicolin appeared to be a peptide composed of 27 amino acids, glycosylated on the second residue, with a N-terminal pyroglutamic acid and 6 cysteines involved in disulfide bonds. Its molecular mass was estimated to be 2885 Da. No significant sequence homology with other proteins could be found. The availability of pure toxin in sufficient amount is a prerequisite for its structure determination, which is a key step in the understanding of the aggression mechanism.
Amino Acid Sequence↗
Inhibition of the growth of Paenibacillus larvae, the causal agent of American foulbrood of honeybees, by selected strains of aerobic spore-forming bacteria isolated from apiarian sources.
The bacterium Paenibacillus larvae, the causative agent of American foulbrood disease of honeybee larvae, occurs throughout the world and is found in many beekeeping areas of Argentina. The potential as biocontrol agents of antagonic aerobic spore-forming bacteria isolated from honey samples and other apiarian sources were evaluated. Each isolate was screened against one strain of Paenibacillus larvae (ATCC 9545) by using a perpendicular streak technique. Ten randomly selected bacterial strains from the group that showed the best antagonistic effect to P. larvae ATCC 9545 were selected for further study. These were identified as Bacillus subtilis (m351), B. pumilus (m350), B. licheniformis (m347), B. cereus (mv33), B. cereus (m387), B. cereus (m6c), B. megaterium (m404), Brevibacillus laterosporus (BLAT169), B. laterosporus (BLAT170), and B. laterosporus (BLAT171). The antagonistic strains were tested against 17 P. larvae strains from different geographical origins by means of a spot test in wells. The analysis of variance and posterior comparison of means by Tukey method (P < 0.01) showed that the best antagonists were B. megaterium (m404), B. licheniformis (m347), B. cereus (m6c), B. cereus (mv33), and B. cereus (m387).
Animals↗
Structures for the potential drug target purine nucleoside phosphorylase from Schistosoma mansoni causal agent of schistosomiasis.
Despite the availability of effective chemotherapy, schistosomiasis continues to be one of the major parasitic infections to affect the human population worldwide. Currently, little is known of the structural biology of the parasites that are responsible for the disease and few attempts have been made to develop second generation drugs, which may become essential if resistance to those currently available becomes an issue. Here, we describe three crystal structures for the enzyme purine nucleoside phosphorylase (PNP) from Schistosoma mansoni, a component of the purine salvage pathway. PNP is known to be essential for the recovery of purine bases and nucleosides in schistosomes, due to an absence of the enzymes for de novo synthesis, making it a sensitive point in the parasite's metabolism. In all three structures reported here, acetate occupies part of the base-binding site and is directly bound to the conserved glutamic acid at position 203. One of the structures presents the crystallization additive sulfobetaine 195 (NDSB195) occupying simultaneously the ribose and phosphate binding sites, whilst a second presents only phosphate in the latter. The observation of sulfobetaine specifically bound to the protein active site was unexpected and is unique to this structure as far as we are aware. Considerable flexibility is observed in the active site, principally due to variable structural disorder in the regions centered on residues 64 and 260. This conformational plasticity extends to the way in which both NDSB195 and phosphate bind to the individual monomers of the trimeric structure reported here. Differences between the parasite and human enzymes are limited principally to the base-binding site, where the substitution of V245 in the mammalian enzymes by S247 introduces additional hydrogen bonding potential to the site. This is satisfied in the structures described here by a water molecule whose presence is normally observed only in complexes with 6-oxopurines. Residue Y202, which replaces F200 in human PNP, is able to reach over the ribose-binding site to interact with H259 and is predicted to form an additional hydrogen bond with the 5' hydroxyl of nucleoside substrates.
Amino Acid Sequence↗
A rapid and sensitive method for the detection of Xanthomonas fragariae, causal agent of angular leafspot disease in strawberry plants.
Angular leaf spot is a bacterial disease caused by Xanthomonas fragariae. It has become a serious disease in the USA and Europe in recent years. Several detection procedures are described for this plant pathogen. However, they are either too time-consuming, too insensitive or impractical when handling a large number of samples routinely. Here we describe a modified protocol of the REDExtract-N-Amp Plant PCR-Kit for the detection of X. fragariae in planta and demonstrate that it provides greater sensitivity, speed and high throughput potential than methods previously described.
Bacteriological Techniques↗
A molecular protocol using quenched FRET probes for the quarantine surveillance of Tilletia indica, the causal agent of Karnal bunt of wheat.
The current surveillance protocol for Karnal bunt of wheat in most countries, including the USA, European Union (EU), and Australia, involves the tentative identification of the spores based on morphology followed by a molecular analysis. Germination of spores is required for confirmation which incurs a delay of about two weeks, which is highly unsatisfactory in a quarantine situation. A two-step PCR protocol using FRET probes for the direct detection and identification of Tilletia indica from a very few number of spores (< or =10) is presented. The protocol involves amplification of the ITS1 DNA segment in the highly repeated rDNA unit from any Tilletia species, followed by FRET analysis to detect and unequivocably distinguish T. indica and the closely related T. walkeri. This rapid, highly sensitive, fluorescent molecular tool is species-specific, and could supersede the conventional microscopic diagnosis used in a quarantine surveillance protocol for Karnal bunt which is often confounded by overlapping morphological characters of closely related species.
DNA, Fungal↗
Amebae and ciliated protozoa as causal agents of waterborne zoonotic disease.
The roles free-living amebae and the parasitic protozoa Entamoeba histolytica and Balantidium coli play as agents of waterborne zoonotic diseases are examined. The free-living soil and water amebae Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris are recognized etiologic agents of mostly fatal amebic encephalitides in humans and other animals, with immunocompromised and immunocompetent hosts among the victims. Acanthamoeba spp. are also agents of amebic keratitis. Infection is through the respiratory tract, breaks in the skin, or by uptake of water into the nostrils, with spread to the central nervous system. E. histolytica and B. coli are parasitic protozoa that cause amebic dysentery and balantidiasis, respectively. Both intestinal infections are spread via a fecal-oral route, with cysts as the infective stage. Although the amebic encephalitides can be acquired by contact with water, they are not, strictly speaking, waterborne diseases and are not transmitted to humans from animals. Non-human primates and swine are reservoirs for E. histolytica and B. coli, and the diseases they cause are acquired from cysts, usually in sewage-contaminated water. Amebic dysentery and balantidiasis are examples of zoonotic waterborne infections, though human-to-human transmission can occur. The epidemiology of the diseases is examined, as are diagnostic procedures, anti-microbial interventions, and the influence of globalization, climate change, and technological advances on their spread.
Acanthamoeba↗
Human herpesvirus 7: another causal agent for roseola (exanthem subitum).
Human herpesvirus 7 (HHV-7) was isolated from peripheral blood mononuclear cells of two infants with typical exanthem subitum. The HindIII-, BamHI-, and EcoRI-digested DNA patterns of the isolated viruses were very similar to that of the prototype HHV-7 (RK strain), but different from that of human herpesvirus 6 (HHV-6). During the convalescent period of the first patient, the titer of antibody to HHV-7 rose from < 1:10 to 1:320 by an immunofluorescence antibody test, whereas the titer of antibody to HHV-6 remained < 1:10. In the second patient, who had two independent episodes of exanthem subitum during 2 months, both HHV-6 and HHV-7 were sequentially isolated; seroconversion to HHV-6 occurred during the first episode and to HHV-7 during the second episode. In addition, sera from another 15 children who had episodes of exanthem subitum were serologically tested for antibodies to HHV-6 and HHV-7 by immunofluorescence antibody test. Five of seven patients had seroconversion to HHV-7 just after having typical signs and symptoms of exanthem subitum. These results suggest that HHV-7 is one of the causative agents of exanthem subitum.
Child, Preschool↗
Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong.
BACKGROUND: Health authorities worldwide, especially in the Asia Pacific region, are seeking effective public-health interventions in the continuing epidemic of severe acute respiratory syndrome (SARS). We assessed the epidemiology of SARS in Hong Kong. METHODS: We included 1425 cases reported up to April 28, 2003. An integrated database was constructed from several sources containing information on epidemiological, demographic, and clinical variables. We estimated the key epidemiological distributions: infection to onset, onset to admission, admission to death, and admission to discharge. We measured associations between the estimated case fatality rate and patients' age and the time from onset to admission. FINDINGS: After the initial phase of exponential growth, the rate of confirmed cases fell to less than 20 per day by April 28. Public-health interventions included encouragement to report to hospital rapidly after the onset of clinical symptoms, contact tracing for confirmed and suspected cases, and quarantining, monitoring, and restricting the travel of contacts. The mean incubation period of the disease is estimated to be 6.4 days (95% CI 5.2-7.7). The mean time from onset of clinical symptoms to admission to hospital varied between 3 and 5 days, with longer times earlier in the epidemic. The estimated case fatality rate was 13.2% (9.8-16.8) for patients younger than 60 years and 43.3% (35.2-52.4) for patients aged 60 years or older assuming a parametric gamma distribution. A non-parametric method yielded estimates of 6.8% (4.0-9.6) and 55.0% (45.3-64.7), respectively. Case clusters have played an important part in the course of the epidemic. INTERPRETATION: Patients' age was strongly associated with outcome. The time between onset of symptoms and admission to hospital did not alter outcome, but shorter intervals will be important to the wider population by restricting the infectious period before patients are placed in quarantine.
Adolescent↗
Detection of each of the causal agents of groundnut rosette disease in plants and vector aphids by RT-PCR.
Detection of the three agents of groundnut rosette disease (groundnut rosette assistor virus, groundnut rosette virus and its satellite RNA) in plants and vector aphids by reverse transcription-polymerase chain reaction (RT-PCR) is reported. Three procedures for extraction of total RNA from groundnut were tested, of which two were found to be useful in giving RNA of sufficient quality for RT-PCR. Of these two, the total RNA extraction kit supplied by Qiagen was found to be the most versatile for extraction of all three agents from individual vector aphids (Aphis craccivora). Both groundnut rosette assistor virus and groundnut rosette virus could be detected from total RNA extracted from a single aphid that had been exposed to either green or chlorotic rosette-infected groundnut plants. They could be detected in aphids stored in 70% ethanol for up to 30 days at room temperature. However, satellite RNA could be amplified only when total RNA extracted from two or more aphids was used. Groundnut rosette assistor virus, groundnut rosette virus and its satellite RNA were detected by RT-PCR in aphids that had been exposed only to groundnut rosette diseased plants containing all three agents. The potential of RT-PCR in studying certain key issues of rosette disease epidemiology is discussed.
Animals↗
Is adrenomedullin a causal agent in some cases of type 2 diabetes?
The study of two populations with a recent onset of type 2 diabetes showed that a subset of the patients had higher levels of adrenomedullin (AM) than the rest of the diabetics. In this subset, physiological elevations of AM might have triggered the disease in predisposed individuals. Diabetics showed higher levels of AM than healthy controls. In addition, glycemia was measured in diabetic rats after injection of saline, AM, or antiAM antibody. AM elevated glycemia, whereas the antibody reduced circulating glucose to normal. These results suggest that manipulation of AM levels could represent a new approach in the management of diabetes for the appropriate individuals.
Adolescent↗
The action of antibiotics and sulphamezathine on the causal agent of virus pneumonia of pigs.
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Animals↗