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W Dott

Publications and source records attributed to W Dott.

At least 55 records · Page 3Linked to original sources
PubMed1992

Fluorogenic substrates for differentiation of gram-negative nonfermentative and oxidase-positive fermentative bacteria.

A total of 803 strains of gram-negative nonfermentative and oxidase-positive fermentative bacteria (38 taxa) were investigated for their ability to hydrolyze 53 different fluorogenic 4-methylumbelliferyl- and beta-naphthylamide-linked substrates within 6 h of incubation. The hydrolysis of 16 fluorogenic substrates showed high separation index values among the tested taxa, was reproducible, and showed good agreement with data in the literature. In combination with other biochemical tests (like carbon substrate utilization tests and classical biochemical tests), hydrolysis profiles can improve the differentiation of gram-negative nonfermentative and oxidase-positive fermentative bacteria.

Chromogenic Compounds↗
PubMed1991

Physiological characterization and identification of Listeria species.

A total of 136 strains of the genus Listeria were physiologically characterized using 329 miniaturized tests. Overall similarities of all strains were determined by numerical taxonomic techniques using the UPGMA algorithm and the SSM and SJ coefficients. A total of 10 clusters (2 or more strains) and 1 single-member cluster were defined at the 95.1 to 95.8% similarity levels (SSM). The same clusters were found at the 76.8% to 77.8% similarity levels (SJ). Strains of L. seeligeri, L. welshimeri, L. ivanovii, L. murrayi and L. grayi were found in separate clusters and formed homogeneous taxospecies. In contrast, strains of L. monocytogenes and L. innocua formed five heterogeneous clusters and one single-member cluster. For differentiation of the phena the following tests are useful: utilization of D-xylose, D-xylitol, D-ribose, D-galactose, alpha-methyl-D-mannoside, methyl-alpha-D-glucopyranoside, inulin and L-rhamnose, acid production from D-glucuronate, alpha-D-galacturonate, alpha-methyl-D-mannoside, methyl-alpha-D-glucopyranoside, D-xylose, L-lyxose, D-sucrose, alpha-D-melizitose, D-tagatose, and D-ribose and hydrolysis of pNP-alpha-D-glucopyranoside, pNP-alpha-D-mannopyranoside and 2-deoxythymidine-5'-pNP-phosphate. Independent of the assignment of some strains of L. monocytogenes and L. innocua to the same cluster, members of these species can be separated by hydrolysis of D-alanine-p-nitroanilide.

Cluster Analysis↗
PubMed1991

Glycosidase profiles of members of the family Enterobacteriaceae.

A total of 712 strains representing 47 taxa of the family Enterobacteriaceae were tested for the ability to hydrolyze 14 4-methylumbelliferyl (4-MU)-linked substrates within 3 h of incubation. In addition to the well-known differentiation potential of the hydrolysis of 4-MU-beta-D-galactopyranoside, 4-MU-beta-D-glucuronide, and 4-MU-beta-D-xylopyranoside, the hydrolysis of some other fluorogenic substrates (e.g., 4-MU-beta-D-fucopyranoside, 4-MU-N-acetyl-beta-D-galactosaminide, and 4-MU-alpha-D-galactopyranoside) can also be used for species differentiation within the family Enterobacteriaceae.

Enterobacteriaceae↗
PubMed1991

[Survival ability of genetically engineered strains of Escherichia coli. 1. Physiological characterization and the effect of different physiochemical conditions].

Two genetically engineered E. coli strains L+ and CAG+ possessing the ability to produce the enzyme Pro-urokinase and showing additionally ampicillin resistance, and wild-strains L- and CAG-, were characterized using 328 physiological tests. Their test profiles were compared with those of 30 clinical and nonclinical E. coli isolates. This biotyping made a differentiation and recognition of the genetically manipulated strains possible. It also allowed distinguishing them from the other tested isolates. The genetically engineered strains showed a narrower activity spectrum compared with their wild-strains. However, based on differentiating characteristics, all strains could be clearly biochemically identified as E. coli. Under different laboratory test conditions (organic load, pH, salt content, temperature), the E. coli strains showed no striking features or peculiarities with respect to their survival compared to data from literature. However, low pH (pH less than 5), high salt content (greater than 7%) as well as low (less than 8 degrees C) and high (greater than 37 degrees C) incubation temperatures clearly reduced their ability to survive. Apart from a few exceptions (e.g. survival of strain L+ at 44 degrees C and pH 7 with high cell densities), the survival of the genetically engineered strains corresponded to that of the control and wild-strains. Both CAG strains, especially the genetically manipulated strain CAG+, showed in many cases reduced viability compared with the other strains.

Bacterial Typing Techniques↗
PubMed1991

[Survival capacity of genetically altered Escherichia coli strains. 2. Survival of pure cultures in different water and soil matrices].

The survival of two genetically engineered E. coli strains (L+, CAG+) compared to that of 4 control strains (N0, K12, L-, CAG-), was investigated in drinking water, surface water, sewage and soil under different conditions. Both genetically manipulated strains are able to produce Prourokinase, an anticoagulant. It was found, that all strains died off inspite of high inoculated bacterial densities. In drinking water, no bacteria could be recultivated immediately following inoculation. Upon inoculation in surface water, the genetically manipulated strains L+ and CAG+ were more sensitive than the other strains. The same was found for sewage under aerobic conditions, whereby, the control strains N0 and K12 as well as the wild-strains of the genetically manipulated organisms, L- and CAG- survived the whole experimental period and kept their numbers at a level between 100 and 1000 CFU/ml. Under anaerobic conditions, a die-off of all tested strains was similarly registered with time. The influence of the autochthonous microflora of sewage water could be documented in that, under these conditions, all test strains survived the whole experimental period of 31 days with the exception of the genetically manipulated strain CAG+. In soil experiments, it was found that the humus-rich garden soil was more effective in eliminating the E. coli strains than sand. The antagonistic effect of the autochthonous soil microflora was only clearly seen in experiments with garden soil. However, these results did not meet the expectations for the two CAG strains, for which a longer survival period had been previously established for in nutrient rich soil. In contrast to the E. coli control strains N0 and K12, the two L strains and the CAG+ strain survived the whole test period of 36 days. It can be concluded that under these simulated environmental conditions, all tested strains of E. coli die off more or less in a short period of time following inoculation with the autochthonous microflora of environmental samples.

Aerobiosis↗
PubMed1990

[Effect of the isolation medium and isolation conditions on the isolation of the bacterial species spectrum in drinking water].

With the method of colony-count estimation according to German standards (Trinkwasserverordnung, TVO), bacteria of the genera Aeromonas, Shewanella, Pseudomonas etc. and (if present) representatives of the family Enterobacteriaceae can be detected. Longer incubation and application of low nutrient media enhance the colony counts up to 100-fold, and other bacteria can be isolated, in most cases belonging to the genera Pseudomonas, Alcaligenes, Acinetobacter, Flavobacterium etc.. For the detection of hygienically relevant bacteria (e.g. indicator bacteria) the methods of TVO are sufficient and their routine use is recommended. For further microbiological-ecological studies on the habitat drinking water, the nutrient poor biotope has to be considered and the applied media and methods should be adapted to these requirements.

Aeromonas↗
PubMed1989

Evaluation of the Titertek-NF system for identification of gram-negative nonfermentative and oxidase-positive fermentative bacteria.

The Titertek-NF (TT-NF) system (Flow Laboratories GmbH, Meckenheim, Federal Republic of Germany) was evaluated for the identification of 1,289 strains of gram-negative, nonfermentative bacteria and some gram-negative, oxidase-positive bacteria. The oxidase test was also performed. Identifications were classified as correct, not identified (two or more taxa possible and identification score of less than 80%; supplementary tests for furthering the identification were not performed), and incorrect. Correct identification results were further subdivided by the correct level of species or biotype identification as greater than or equal to 98% (category a), 90 to 97% (category b), and 80 to 89% (category c). When compared with conventional identification results, the TT-NF system correctly identified 90.3% of strains (1,164 of 1,289 strains), with 72.5% (935 strains) belonging to category a, 14.7% of strains (189 strains) belonging to category b, and 3.1% of strains (40 strains) belonging to category c. Among the remaining strains, 104 (8.1%) were not identified and 14 (1.1%) were misidentified, and the system failed to generate identification results for 7 strains (0.5%). Reactions within the TT-NF system were reproducible, with an estimated probability of erroneous test results of 0.2%.

Fermentation↗
PubMed1989

[Numerical identification of aquatic microorganisms using automated methods; for example, identification of bacteria from activated sludge].

A probability matrix for numerical identification of aquatic microorganisms was constructed using 90 miniaturized biochemical tests. More than 2000 reference strains originated from different culture collections and environmental strains identified by conventional methods were included in this matrix. All test result can be read visually and by photometer (automatically). First applications of this system on aerobic and facultative anaerobic heterotrophic organisms from activated sludge revealed the advantage of this system compared to conventional methods and delivered further a detailed description of the activated sludge community.

Bacteria↗
PubMed1989

[The identification of microorganisms from groundwater and characterization of their physiologic activities].

The microbiological method presented in this contribution allows the following investigations: --Identification of aerobic, heterotrophic environmentally-related organisms. --Investigation of different physiological activities of the test bacteria (e.g., degradation of different organic carbonaceous compounds, formation of extracellular enzymes). --Characterization of biological communities and their diversity. --Estimation of activities in environmental samples and mixed cultures. --Evaluation of a micro-site quality, e.g., reductions in the numbers of species or in a specific activity due to the effects of toxic substances. --Monitoring of the microbial community and its activities during biorestoration processes.

Bacteria↗
PubMed1988

Growth dependent enzymatic profiles of some gram-negative nonfermentative bacteria of clinical significance.

A total of 734 strains of gram-negative nonfermentative bacteria (46 species and biochemically defined groups) of the genera Pseudomonas, Alcaligenes, Bordetella, Moraxella, Acinetobacter, Agrobacterium, and Flavobacterium were investigated for their ability to hydrolyze 25 different chromogenic substrates. All tests were carried out in growth-stimulating media. Results were read photometrically and evaluated automatically following a 24-h incubation. Many of the 46 different species and biochemical groups exhibited uniform patterns of enzyme production. Some of the enzyme tests may serve as additional valuable tools for differential diagnosis of the organisms investigated. In combination with other biochemical tests, qualitative enzyme demonstration tests can facilitate the identification of gram-negative nonfermentative bacteria.

Acinetobacter↗
PubMed1988

Differentiation of some gram-negative glucose nonfermenting bacteria using miniaturized carbon sources assimilation tests.

In water and soil the gram-negative nonfermenting bacteria play an important role in the biological mineralization process. To improve the methods for species differentiation of these heterogenous bacterial group, a total of 481 reference strains of gram-negative glucose nonfermenting bacteria belonging to the genera Pseudomonas, Alcaligenes, Bordetella, Agrobacterium, Moraxella, Acinetobacter, Flavobacterium and some CDC groups have been investigated for their ability to utilize 42 different carbon substrates with the help of a standardized and automated micromethod. Most species showed a typical pattern of carbon utilization and hence could be differentiated from each other within their genera. As already has been demonstrated by more clinical significant Pseudomonas species, this method proves to be a useful alternative to existing methods of differentiation, especially with representatives of the families Pseudomonadaceae and Alcaligenaceae.

Acinetobacter↗
PubMed1987

Phenotypic differentiation of members of the family Vibrionaceae using miniaturized biochemical tests.

Enzymatic hydrolysis of 27 different chromogenic substrates and the assimilation of 44 carbon sources by 144 strains of Vibrio species of clinical importance, Aeromonas hydrophila and Plesiomonas shigelloides were studied by standardized micromethods. Some classical biochemical tests were also performed using the test kit TTE-AS (Flow Laboratories GmbH, Meckenheim, FRG). Reading of results was done automatically by a photometer and test data were recorded and stored by a microcomputer. All species investigated could be differentiated using a set of 16 miniaturized biochemical tests which are: Indole production, esculin hydrolysis, lysine decarboxylase, ornithine decarboxylase, arginine dihydrolase, fermentation of sucrose, enzymatic hydrolysis of o-nitrophenyl-beta-D-galactopyranoside, gamma-L-glutamic acid-p-nitroanilide and the assimilation of L-arabinose, D-cellobiose, D-mannose, sucrose, D-mannitol, i-inositol, acetate and DL-lactate. Comparing the TTE-AS tests to conventional test results, 94.4% overall agreement was found. 87.6% of the miniaturized assimilation tests agreed to literature data. The described tests are easy to perform and seem to be suitable for routine laboratory use.

Aeromonas↗
PubMed1987

Survival of selected bacterial species in sterilized activated carbon filters and biological activated carbon filters.

The survival of selected hygienically relevant bacterial species in activated carbon (AC) filters on a bench scale was investigated. The results revealed that after inoculation of the test strains the previously sterilized AC absorbed all bacteria (10(6) to 10(7)). After a period of 6 to 13 days without countable bacteria in the effluent, the numbers of Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas putida increased up to 10(4) to 10(5) CFU/ml of effluent and 10(6) to 10(7) CFU/g of AC. When Klebsiella pneumoniae and Streptococcus faecalis were used, no growth in filters could be observed. The numbers of E. coli, P. aeruginosa, and P. putida, however, decreased immediately and showed no regrowth in nonsterile AC from a filter which had been continuously connected to running tap water for 2 months. Under these conditions an autochthonous microflora developed on the carbon surface which could be demonstrated by scanning electron microscopy and culturing methods (heterotrophic plate count). These bacteria reduced E. coli, P. aeruginosa, and P. putida densities in the effluent by a factor of more than 10(5) within 1 to 5 days. The hypothesis that antagonistic substances of the autochthonous microflora were responsible for the elimination of the artificial contamination could not be confirmed because less than 1% of the isolates of the autochthonous microflora were able to produce such substances as indicated by in vitro tests. Competition for limiting nutrients was thought to be the reason for the observed effects.

Antibiosis↗
PubMed1987

[Automated micromethod for the determination of the utilization of carbon sources by clinically significant Pseudomonas species].

The assimilation of 43 different carbon substrates by 93 clinical strains of Pseudomonas aeruginosa was studied by a new miniaturized rapid method. Reading of assimilation results was done photometrically after 18-20 h incubation and the resulting data were captured and stored by a microcomputer. The differentiating capacity of the assimilation tests were verified by comparing the results of 41 strains of Pseudomonas fluorescens, 48 strains of Pseudomonas putida, 52 strains of Pseudomonas maltophilia and respectively 10 strains of Pseudomonas pseudomallei and Pseudomonas cepacia. The assimilation pattern obtained from the Pseudomonas aeruginosa strains agreed to those described in literature and because of miniaturization, standardisation, facility of use and automatic reading the method seems to be suitable for routine laboratory work.

Amino Acids↗
PubMed1987

[Occurrence and incidence of bacteria in the area of drinking water with antagonistic relations to indicator bacteria].

During a period of 8 months about 3000 drinking water samples derived from different water works and distribution systems around the area of the city Bonn were examined for colony count, E. coli and coliform bacteria and bacteria suppressing the growth of E. coli and S. faecalis. A modified agar diffusion test was used for the determination of antagonistic substances. Bacteria which revealed an antagonistic activity were isolated and identified. The majority of water samples (81.9% of the samples examined for antagonistic bacteria against E. coli) contained no bacteria in 1 ml and therefore were not examined for antagonistic substances. Only 2.5% of the samples had bacterial counts greater 100 per ml. In 64.2% of the samples examined for bacteria antagonistic to S. faecalis, no counts were found and 2.4% had counts greater 100. The occurrence of fecal indicators was very low in samples with low colony forming units (cfu). At counts greater than 100 we found E. coli within 30.6% and coliform bacteria in 38.8% of the samples examined for bacteria showing antagonistic activity against E. coli. E. coli and coliform bacteria were determined in 24.2% and 33.3% of the samples examined for antagonistic bacteria against S. faecalis. 20% of the samples with colony counts between 1 to 10 contained bacteria showing antagonistic activity against E. coli and at counts greater than 100 they were found in 57.1% of the samples. On the other hand, the quantity of samples with suppression of S. faecalis was 10 to 20% lower and reached a maximum of 39.4% at cfu greater 100. Most of the isolated antagonistic strains belong to the genus Pseudomonas and even 57.8% of the inhibitory strains against E. coli and 26.5% against S. faecalis were found to be P. fluorescens.

Bacteriological Techniques↗
PubMed1987

[Ability to survive and interactions of selected bacterial species in activated carbon filters].

The survival and the interactions of selected, hygienically relevant bacterial species in activated carbon filters was investigated. The numbers of Escherichia coli, Pseudomonas aeruginosa and P. putida increased in previously sterilized filters. After inoculation all bacteria (10(6] were adsorbed. During a period of 6-10 days the filter effluent contained no detectable bacteria. After that the colony numbers increased to a constant level of 10(4)-10(5) colony forming units (CFU)/ml effluent and 10(6)-10(7) CFU/g activated carbon. Klebsiella pneumoniae and Streptococcus faecalis died off in the filter system. If the filters were inoculated simultaneously with two species, P. putida and P. aeruginosa remained at a constant level between 10(4) and 10(5) CFU/ml. E. coli was suppressed by P. aeruginosa and died off in the presence of P. putida. As in-vitro tests indicated, P. putida did not produce inhibitory substances against P. aeruginosa or E. coli. On the other hand, P. aeruginosa showed antagonistic activities against E. coli.

Bacterial Physiological Phenomena↗
PubMed1986

[Microbiology of ground water and drinking water].

Groundwater has been considered a safe source for drinking water protected against surface contamination. However, a number of reports about chemical and microbiological contamination have disproved this assumption. Besides hygienical monitoring, little is known about the microbiology of ground- and drinking water. The purpose of this paper is to give a review about the main fields of investigation concerning microbial activity in ground- and drinking-water-action. The hygienical relevant topics are: survival and transport of microorganisms, microbiological degradation of organic pollutants, turn-over of nitrogen compounds, oxidation and reduction of iron and manganese and development of methods for microbiological water examination.

Fresh Water↗