PubMed · 7791472
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S E Patchett, H E Mulcahy, M J Farthing. 1995-06-17. String test for Helicobacter pylori.. https://doi.org/10.1016/s0140-6736(95)91133-2
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We recently developed a simple new method which is designed to separate and concentrate bacteria from a sample by centrifugation in a gel system. Bacterial enzyme activity is then detected inside the gel without further manipulation using a colorimetric or fluorogenic substrate. The method provides a rapid, direct means of detecting bacteria in clinical samples, dispensing with the 24-h period normally required to isolate colonies on agar. Various applications of the method are described below, e.g. screening of negative urine samples, identification of Escherichia coli in urine samples, identification of Staphylococcus aureus in blood culture broths and detection of oxacillin-resistant S. aureus in blood culture broths. The advantages of the gel system and other applications are discussed.
An environmental isolate of Salmonella typhi was chromosomally marked with a gfp gene encoding green fluorescence protein (GFP) isolated from Aequorea victoria. The hybrid transposon mini Tn5 gfp was transconjugated from E. coli to S. typhi, resulting in constitutive GFP production. The survival of S. typhi GFP155 introduced into groundwater and pond water microcosms was examined by GFP-based plate counts, total cell counts, and direct viable counts. A comparison between GFP-based direct viable counts and plate counts was a good method for verifying the viable, but non-culturable (VBNC), state of S. typhi. The entry into a VBNC state of S. typhi was shown in all microcosms. S. typhi survived longer in groundwater than in pond water as both a culturable and a VBNC state.
Contaminated sediments influence drastically the long-term toxicological and ecological properties of aquatic ecosystems. During the past three decades, scientific knowledge about sediment-water exchange processes and the deposition and distribution of pollutants in water and sediment phases has been supplemented by extensive research on the effects of sediment-associated pollutants on aquatic organisms. Basic research in microbiology, ecology, and toxicology has uncovered the crucial role of sediment microorganisms for the biodegradation of organic matter and for the cycling of nutrients, as well as the susceptibility of these processes to toxic pollution events. Microorganisms have been extensively applied in aquatic toxicology, and various microbial toxicity tests are today available that successfully couple microbial toxicity endpoints to the specificity of the sediment matrix. Sediment-associated toxicants can be brought in contact with test bacteria using sediment pore waters, elutriates, extracts, or whole-sediment material. Toxicity indication principles for microorganisms are versatile and comprise growth and biomass determinations, respiration or oxygen uptake, bacterial luminescence, the activity of a variety of enzymes, and a compendium of genotoxicity assays. The border between toxicological and ecological contaminant effect evaluations in sediments is flexible, and long-term ecological predictions should also include an assessment of pollutant degradation capacities and of key reactions in element cycling. Evaluating microbial community structure and function in environmental systems makes use of modern molecular techniques and bioindicators that could trigger a new quality in the assessment of contaminated sediments in terms of indication of subtoxic effects and early-warning requirements.