PubMed Health⌕ Search

Biomedical subjects

David Ammons

Publications and source records attributed to David Ammons.

5 recordsLinked to original sources
PubMed2005

A Bacillus thuringiensis isolation method utilizing a novel stain, low selection and high throughput produced atypical results.

BACKGROUND: Bacillus thuringiensis is a bacterium known for producing protein crystals with insecticidal properties. These toxins are widely sought after for controlling agricultural pests due to both their specificity and their applicability in transgenic plants. There is great interest in isolating strains with improved or novel toxin characteristics, however isolating B. thuringiensis from the environment is time consuming and yields relatively few isolates of interest. New approaches to B. thuringiensis isolation have been, and continue to be sought. In this report, candidate B. thuringiensis isolates were recovered from environmental samples using a combination of a novel stain, high throughput and reduced selection. Isolates were further characterized by SDS-PAGE, light microscopy, PCR, probe hybridization, and with selected isolates, DNA sequencing, bioassay or Electron Microscopy. RESULTS: Based on SDS-PAGE patterns and the presence of cry genes or a crystal, 79 candidate, non-clonal isolates of B. thuringiensis were identified from 84 samples and over 10,000 colonies. Although only 16/79 (20%) of the isolates showed DNA homology by Probe Hybridization or PCR to common cry genes, initial characterization revealed a surprisingly rich library that included a putative nematocidal gene, a novel filamentous structure associated with a crystal, a spore with spikes originating from a very small parasporal body and isolates with unusually small crystals. When compared to reports of other screens, this screen was also atypical in that only 3/79 isolates (3.8%) produced a bipyramidal crystal and 24/79 (30%) of the isolates' spores possessed an attached, dark-staining body. CONCLUSION: Results suggest that the screening methodology adopted in this study might deliver a vastly richer and potentially more useful library of B. thuringiensis isolates as compared to that obtained with commonly reported methodologies, and that by extension, methodologies fundamentally different from current methods should also be explored.

Animals↗
PubMed2003

A field evaluation of PCR for the routine detection of Babesia equi in horses.

We report on a study that evaluated the usefulness of PCR for the routine detection of Babesia equi in horses. The blood from a total of 105 horses comprising both sick and apparently healthy animals were examined for the presence of B. equi using both Wright-Giemsa-stained blood smears and PCR. Microscopic analysis of Giemsa-stained blood smears revealed 10/105 animals positive for Babesia, compared to 16/105 for the primary PCR and 36/105 for the nested PCR. Three of the 10 samples positive by Wright-Giemsa-stain were negative by PCR for B. equi. However, evidence is presented that these samples contained B. caballi and not B. equi. The Wright-Giemsa-stain was shown to identify Babesia in mostly clinically ill animals while the nested PCR detected the organism in a large number of apparently healthy animals. The results of this study suggest that the nested PCR is superior to both Wright-Giemsa-stained and primary PCR methods, and should be considered for the routine detection of B. equi in both healthy and clinically ill horses.

Animals↗
PubMed2003

A Bacillus thuringiensis isolate possessing a spore-associated filament.

We report on a novel bacterium, isolated during a screen for environmental isolates of Bacillus thuringiensis, that possesses a novel filamentous structure. Nucleotide sequence from the isolate's 16S rRNA gene places the bacterium unambiguously within the Bacillus thuringiensis/Bacillus cereus group. Phase-contrast and electron microscopy indicate the presence of both a parasporal body and a long filament which are retained after sporulation. The filament is shown to consistently arise from the end of the exosporium and next to the parasporal body. Upon spore germination, the parasporal body/filament complex is retained on the cell wall of the resulting bacterium.

Bacillus thuringiensis↗
PubMed2002

Molecular characterization of rabies virus isolates from Trinidad.

Bovine rabies continues to be a serious problem facing the cattle industry in South and Central America. Although Trinidad played an important role in originally demonstrating the link between bats and bovine rabies, relatively little is known about rabies in Trinidad, an island 7miles off the coast of Venezuela. In order to obtain a more complete understanding of bovine rabies in the region, we report herein on a study undertaken in Trinidad to characterize isolates of rabies virus obtained from infected cattle. A portion of the nucleotide sequence of the nucleoprotein gene from six rabies virus isolates collected from bovine rabies from the years 1997, 1998 and 2000 was determined and compared both to themselves and the nucleotide sequence of other South American isolates. Results indicate that there are at least two independently evolving variants of rabies virus in Trinidad. The nucleotide sequence of either variant failed to match completely the sequence of South American isolates. However, the lack of South American isolates from coastal regions facing Trinidad leaves undetermined the question of South American influence on rabies in Trinidad. The results of this study helps complete the picture of bovine rabies in the South American region and provide basic information required locally for the creation of an effective rabies control and eradication strategy.

Animals↗