Adhesion of Pseudomonas aeruginosa,Achromobacter xylosoxidans,Delftia acidovorans,Stenotrophomonas maltophilia to contact lenses under the influence of an artificial tear solution

Abstract

Corneal infection is a devastating sight-threatening complication that is associated with contact lens (CL) wear, commonly caused by Pseudomonas aeruginosa. Lately, Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia have been associated with corneal infection. This study investigated the adhesion of these emerging pathogens to CLs, under the influence of an artificial tear solution (ATS) containing a variety of components commonly found in human tears. Two different CL materials, etafilcon A and senofilcon A, either soaked in an ATS or phosphate buffered saline, were exposed to the bacteria. Bacterial adhesion was investigated using a radio-labeling technique (total counts) and plate count method (viable counts). The findings from this study revealed that in addition to P. aeruginosa, among the emerging pathogens evaluated, A. xylosoxidans showed an increased propensity for adherence to both CL materials and S. maltophilia showed lower viability. ATS influenced the viable counts more than the total counts on CLs.     

Impact of molecular biology on the detection of foodborne pathogens

Molecular biological methods that use antibodies and nucleic acids to detect specific foodborne bacterial pathogens were scarcely known a decade and a half ago. Few scientists could have predicted that these tools of basic research would come to dominate the field of food diagnostics. Today, a large number of cleverly designed assay formats using these technologies are available commercially for the detection in foods of practically all major established pathogens and toxins, as well as of many emerging pathogens. These tests range from very simple antibody-bound latex agglutination assays to very sophisticated DNA amplification methods. Although molecular biological assays are more specific, sensitive, and faster than conventional (often cultural) microbiological methods, the complexities of food matrices continue to offer unique challenges that may preclude the direct application of these molecular biological methods. Consequently, a short cultural enrichment period is still required for food samples prior to analysis with these assays. The greater detection sensitivity of molecular biological methods may also affect existing microbiological specifications for foods; this undoubtedly will have repercussions on the regulatory agencies, food manufacturers, and also consumers. The US government has the right to retain a nonexclusive royalty-free license in and to any copyright covering this article. Use of trade names is for identification only and does not imply an endorsement by the US FDA.     

Apical meristems of tomato roots and their modifications induced by arbuscular mycorrhizal and soilborne pathogenic fungi

Functional morphological patterns in root apices of tomato ( Lycopersicon esculentum ) dependent on growth, ageing and infection by the arbuscular mycorrhizal (AM) fungus Glomus mosseae and/or by the soilborne pathogenic fungus Phytophthora nicotianae var parasitica ( P. parasitica ) were studied. Uninfected root apices were characterized by closed, tri-layered meristems with nonreticulate nuclei; however, some apices of each treatment lost their meristematic nature, stopped growing and differentiated, becoming 'parenchymatized'. The pathogenic fungus reduced the apex diameter and the number of mitotically active and viable apices inducing plasmolysis, cell and nucleus degeneration, and necrosis. The AM fungus, on the other hand, produced an increase in apex size and reduced the percentage of necrosis both in uninfected roots and in roots infected by P. parasitica . Thus, the AM fungus protected the apices from the pathogenic infection, allowing normal root growth. Furthermore, larger apices, which produce thicker roots, might indirectly contribute to plant protection. Increased volumes of colonizable tissues favour the spreading of the symbiont, and P. parasitica hyphae are always excluded from arbuscule-containing cells.     

Magnetic capture hybridisation for improved PCR detection ofNectria galligena from lignified apple extracts

In order to reduce the effects of inhibitors present in DNA extracts from lignified apple tissues, a magnetic capture-hybridisation PCR (MCH-PCR) technique was developed forNectria galligena using the ITS 1 region of the rRNA gene repeats as target. The trapping reagent used to coat the magnetic beads was an 81 bp single-stranded DNA oligonucleotide biotin-labelled on the 5é-terminal and designed to be complementary to part of the rRNA gene ITS 1 region ofN. galligena. For specificity, the probe was located from 14 bp downstream from the 3é-terminal nucleotide of theN. galligena forward primer Ch1 to the last ITS 1 nucleotide immediately upstream of the 5.8S rRNA gene. Following hybridisation in a total DNA extract of woody tissue, magnetic recovery of the bead-oligomer-template conjugate separated target template from other DNA species and inhibitory compounds. Magnetic capture-hybridisation was followed by PCR amplification with the previously designed species-specific primers, Ch1 and Ch2. Application of the MCH-PCR technique resulted in increased levels of sensitivity and reliability when compared to PCR without MCH when used on total DNA extracts from lignified tissues.     

Development of duplex PCR for the detection of Salmonella and Vibrio in drinking water

We report here a rapid protocol for the detection of Vibrio and Salmonella in drinking water using a duplex PCR reaction. The developed protocol can detect as few as 500 cells in a single reaction, which has been achieved by optimizing the temperature steps and magnesium chloride concentration for the reactions. The described PCR protocol could detect Vibrio and Salmonella spiked in drinking water.     

Antibacterial substances from marine algae isolated from Jeddah coast of Red sea,Saudi Arabia

Marine algae are known to produce a wide variety of bioactive secondary metabolites and several compounds have been derived from them for prospective development of novel drugs by the pharmaceutical industries. However algae of the Red sea have not been adequately explored for their potential as a source of bioactive substances. In this context Ulva reticulata, Caulerpa occidentalis, Cladophora socialis, Dictyota ciliolata, and Gracilaria dendroides isolated from Red sea coastal waters of Jeddah, Saudi Arabia, were evaluated for their potential for bioactivity. Extracts of the algae selected for the study were prepared using ethanol, chloroform, petroleum ether and water, and assayed for antibacterial activity against Escherichia coli ATCC 25322, Pseudomonas aeruginosa ATCC 27853, Stapylococcus aureus ATCC 29213, and Enterococcus faecalis ATCC 29212. It was found that chloroform was most effective followed by ethanol, petroleum ether and water for the preparation of algal extract with significant antibacterial activities, respectively. Results also indicated that the extracts of red alga G. dendroides were more efficient against the tested bacterial strains followed by green alga U. reticulata, and brown algae D. ciliolata. Chemical analyses showed that G. dendroides recorded the highest percentages of the total fats and total proteins, followed by U. reticulata, and D. ciliolate. Among the bioflavonoids determined Rutin, Quercetin and Kaempherol were present in high percentages in G. dendroides, U. reticulata, and D. ciliolate. Estimation of saturated and unsaturated fatty acids revealed that palmitic acid was present in highest percentage in all the algal species analyzed. Amino acid analyses indicated the presence of free amino acids in moderate contents in all the species of algae. The results indicated scope for utilizing these algae as a source of antibacterial substances.     

Virome characterization of game animals in China reveals a spectrum of emerging pathogens

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