Indicator organisms

The most important tests for indicators, which give a microbiological feel for the produce, are the Total Aerobic Viable (plate) Counts (TVAC), and a test for the presence of coliforms as indicators of faecal pollution. Other tests for indicators may be necessary for certain products or under certain storage conditions, e.g. psychrophilic plate counts for items stored at low temperature, anaerobic plate counts for suspect tinned items, and tests for enterococci in cases of suspected food poisoning. In certain items of produce, large numbers of indicator organisms may also pose a threat to health in their own right. 

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In the commonest form of microbiological assay used today, samples to be assayed are applied in some form of reservoir (porcelain cup, paper dise or well) to a thin layer of agar seeded with indicator organism. The drug diffuses into the medium and after incubation a zone of growth inhibition forms, in this case as a circle around the reservoir. All other factors being constant, the diameter of the zone of inhibition is, within limits, related to the concentration of antibiotic in the reservoir. 

Figure 10. Tissue specific expression of p-subunit proteins in floral tissues. Stage 3 (fully opened) flowers were collected, dissected and cell wall proteins (5 pgm) from the indicated organs isolated and analyzed for p-subunit antigen. Note the high level of expression in stigma/style and anthers/pollen and restriction of the larger antigen to stigma/style tissues. PGl lane, 1 gg of purified fruit PGl protein.

Espinel-Ingroff et al. [97] described a radial diffusion bioassay method for miconazole, which employs Candida stellatoidea as the indicator organism. Results from... 

Porte C, Barcelo D, Albaiges J (1992) Monitoring of organophosphorus and organochlori-nated compounds in a rice crop field (Ebro delta, Spain) using the mosquitofish as indicator organism. Chemosphere 24(6) 735-743... 

Boreham, S. and P. Birch. 1987. The use of indicator organisms to assess aquatic pollution following a motorway insecticide spill. Sci. Total Environ. 59 477-480. 

Van der Oost, R., H. Heida, and A. Opperhuizen. 1988. Polychlorinated biphenyl congeners in sediments, plankton, mollusks, crustaceans, and eel in a freshwater lake implications of using reference chemicals and indicator organisms in bioaccumulation studies. Arch. Environ. Contam. Toxicol. 17 721-729. 

Enumeration of sludge pathogens and parasites efficiency of disinfection methods indicator organisms epidemiological aspects of sludge utilisation. Fate of pathogens on land. 

K. Sladek, R. Suslavich, B. Sohn and F. Dawson, paper presented at the Symposium on the Recovery of Indicator Organisms Employing Membrane Filters, sponsored by EPA and ASTM (Committee D-10 on Water), 1977. Difco Manual Ninth Edition, P. 256, 1974. 

First appearance of the indicated organisms —Mass extinctions (the anew length Is proportional to the extent)... 

Conducting studies under controlled conditions with appropriate aquatic and terrestrial indicator organisms to determine the effects of chronic exposure to low doses of inorganic and organic arsenicals on reproduction, genetic makeup, adaptation, disease resistance, growth, and other variables... 

Later studies concerned the detection of both sulfonamides and sulfonamide potentiators in fish tissues. Mixtures containing ethyl acetate, sodium sulfate, and sodium hydroxide (80), or ethyl acetate and sodium hydroxide (115), have been all used for extracting residues of sulfadiazine and trimethoprim from trout and salmon tissues. In the former approach, para-aminobenzoic acid was employed to neutralize sulfadiazine prior to the microbiological assay of trimethoprim, whereas in the latter approach Bacillus subtilis (ATCC) was directly used for sulfadiazine detection. The limit of detection for sulfadiazine using Bacillus subtilis was found to be 0.04 ppm. The test indicator organism used in both approaches to detect trimethoprim down to 0.1 ppm was Bacillus pumilus (CN60 Welcome Research Laboratories, London) (115,116). 

Albrecht, H. 2003. Suitability of arable weeds as indicator organisms to evaluate species conservation effects of management in agricultural ecosystems. Agriculture, Ecosystems and Environment 98(1-3) 201-211. 

The branching ratios shown are estimates based on reference 65. The further oxidation of each of the isomers is similar, so only the first isomer will be examined in detail. In continental areas with at least tens of pptrv s of NO, the peroxy radical produced in the first step will react with NO. This reaction can result in either oxidation of NO to N02 or production of an organic nitrate (bold type indicates organic nitrates that are assumed to be stable) ... 

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