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Biomedical subjects

G Spicher

Publications and source records attributed to G Spicher.

At least 37 records · Page 2Linked to original sources
PubMed1985

[An expedient semi-automatic procedure for the preparation of large quantities of bioindicators especially for use in gas sterilization processes].

Bioindicators serve to test the efficacy of disinfection and sterilization procedures. Such indicators mostly consist of a support (filter paper, as a rule) to which micro-organisms have been fixed by drying. The authors have used a thread as support and a special apparatus for semi-automatic preparation of the bioindicators. The components of the device are either commercially available or may be prepared from commercially available material without difficulty. The principle of the method is as follows: The thread serving as the support is drawn slowly, at constant speed, through the suspension of test organisms and dried in an air stream immediately afterwards. The apparatus consists of a cylindrical glass tube of a few centimeters in diameter, an electric motor slowly rotating the cylinder, a fan, a magnetic stirrer, and an ice-water bath. A small vial containing the germ suspension is immersed in the ice-water bath. The vial is sealed by a screw cap with two glass tubes of about 3 mm inner diameter passing through it. One of the glass tubes being bent in its upper part reaches far down into the vial to leave just enough play for free rotation of a magnetic stirring rod. This tube serves to introduce the thread into the germ suspension. The second straight tube does not reach as far down as the first one. Its lower opening should not be immersed in the germ suspension. This tube serves as a guide for the returning thread. Preparation begins by winding the thread to be soaked with the suspension around the cylinder.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1985

[Method for contaminating test objects with coagulated blood].

A special method to contaminate test objects with blood is described. It is characterized by the use of coagulable blood and its coagulation when adhering to the test objects. Above all, the method is suitable for the microbiological evaluation of the efficacy of agents and methods for the disinfection of surfaces to which coagulated blood will adhere (e.g. instruments). Immediately upon sampling, the blood is heparinized (Liquemin 500 from Hoffmann-La Roche AG at a ratio of 0.1 ml per 100 ml blood). Until use, the coagulable blood is stored at 0 degrees C. For the contamination of test objects, the test organisms are added to the blood (at 0 degrees C), either by mixing the blood with a small amount of a suspension of the test organism or by centrifuging this suspension and dispersing the sedimented organisms in the blood. To start coagulation, Protamin 1000 (Hoffmann-La Roche) is added at a ratio of 0.15 ml per 10 ml blood. Immediately afterwards, the test objects are contaminated with the coagulating blood. Until complete coagulation of the blood, taking ca. 15 min, the test objects are stored in a humid chamber at ca. 20 degrees C.

Blood Coagulation↗
PubMed1985

[Microflora of grain in the cleaning and milling process. 7. Modification of the microbiologic and health quality of grain by product separation].

Food cereals and food cereal products which are consumed directly (without any heart treatment in order to reduce their microflora) should fulfil certain criteria with regard to their microbiological hygienic condition. It can be proved that the microflora of a given cereal batch is differently destributed according to the kernel volumes. Small and light kernels have more microorganisms than heavy kernels. By the separation of certain amount of light kernels (about 15%) from a batch the microbiological condition of the remainder of the batch can be improved. Any separation procedure seizes definite "Besatz" fractions and takes therefore different influence on the microbiological condition of the obtaining cereal fraction, therefore the microbiological condition of the cleaned cereal fraction can be differently affected by the cleaning method. A suitable method for preparation of food cereals is a diagram consisting of: aspirator, light kernels separator, stoner and magnetic separator. In order to get milling products with reduced microbiological germ content the sorting of product can be applied.

Edible Grain↗
PubMed1984

[The microflora of sourdough. XVIII. The protein degrading capabilities of lactic acid bacteria in sourdough].

Acidification of the dough by the use of sourdough or acidifiers is necessary not only for good baking quality of rye flour but it is also very important for development of the typical sensory characteristics of rye bread. We confirmed that the lactic acid bacteria of sour dough are proteolytic. Proteolytic effects are observed in the increase of the amino acid content during fermentation. A marked increase was found in the content of leucine, alanine, valine, isoleucine, glutamic acid, glutamine, arginine, lysine, methionine, phenylalanine, tyrosine and serine. Lactobacillus plantarum showed a higher proteolytic activity than L. brevis ssp. lindneri or L. fructivorans.

Amino Acids↗
PubMed1984

[The microflora of sourdough. XIX. The effect of temperature and dough yield on the proteolytic effect of lactic acid bacteria in sourdough].

During fermentation of sour dough the flour proteins are degraded. The proteolysis depends not only on lactic acid bacteria (Lactobacillus plantarum, L. brevis ssp. lindneri, L. fructivorans) but also on the conditions of fermentation of the sour dough. An increase of temperatures between 25 degrees C and 35 degrees C causes an increase in the amino acid content. The water content of the dough (T.A. 150/T.A. 210) influences the proteolytic activity of the bacteria to a lesser degree.

Amino Acids↗
PubMed1984

[How many biological indicators have to be tested to get reliable information on their resistance?].

Biological indicators are used in the efficacy test of microbicidal procedures. The indicators consist of an object carrying or holding micro-organisms which exhibit resistance to microbicidal agents. The biological indicators are exposed to the procedure to be tested and afterwards examined for viable germs. If test germs are still found to grow in the cultures, the microbicidal effect of the procedure is considered as insufficient. Biological indicators are suitable for such tests only if it is known how intensive the action of the microbicide has to be to destroy the test germs. The individuals of a germ population do not die at the same time under the action of a microbicide. This phenomenon can also be observed with germs simultaneously grown as a pure culture under identical conditions. Therefore, the biological indicators do not become sterile after one and the same period of action or dose of the microbicide but within a certain period or dose range. At the beginning of this transition range, sterile biological indicators will be found very rarely. With increasing period of action or dose, the frequency of indicators carrying viable germs decreases until, eventually, hardly any biological indicators with viable germs are detectable. When samples of identical biological indicators equal in size are exposed to one and the same period of action or dose of a microbicide, the number of indicators carrying viable germs will vary from one sample to another in the transition range. The number of biological indicators that has to be exposed to the resistance test per period of action and dose, respectively, in order to obtain reliable results, can be estimated only if the regularities are known by which the findings vary from one sample to another. Twelve different batches of biological indicators were employed to determine the variation of the resistance values obtained. Spores of Bacillus subtilis served as test germs. The batches differed in the number of spores per biological indicator. The microbicide used was saturated steam of 100 degrees C with a 9 min period of action. Forty-eight samples of five indicators each were taken per batch. The number of indicators carrying viable germs (n+) varied more or less and characteristic frequency distributions were observed (Table 2, columns 3 and 4). Afterwards, the mean relative frequency of indicators with viable germs was calculated for the different batches (Q; Table 2, column 2).(ABSTRACT TRUNCATED AT 400 WORDS)

Bacillus subtilis↗
PubMed1984

[What should be the length and inner diameter of the testing device for microbiological efficacy testing of formaldehyde gas sterilization methods?].

The series of tests described in a preceding publication (Spicher and Borchers, 1983) has been continued in a modified way. This time, the dependency of the microbiological test results of a formaldehyde gas sterilization procedure on length and inner diameter of the tubes serving as test pieces was examined. The tubes were 1 or 2 m in length with an inner diameter of 1 or 2 mm. The tests were performed with four different preparations of bioindicators. Spores of Bac. stearothermophilus served as test germs. The preparations differed in the type of suspension used for the preparation of the bioindicators: distilled water, diluted blood (10%), undiluted blood, 10% albumin solution. The spore suspensions had been dried on linen thread. During the test procedure, the bioindicators were located near the sealed end of the tube. After completion of the sterilization procedure, the bioindicators were examined for viable germs. In tubes of identical length, the frequency of indicators carrying viable germs was always higher in those of 1 mm than in those of 2 mm inner diameter. In tubes of identical inner diameter, the frequency of indicators carrying viable germs in those of 2 m length was always higher than in those of 1 m length. This regularity was independent of the type of bioindicators used. The bioindicators for the preparation of which a 10% albumin solution had been employed showed the highest resistance. A somewhat lower resistance was found for the bioindicators prepared with undiluted blood. The bioindicators for which the spores had been suspended in diluted blood proved to have the lowest resistance. If the spores had been suspended in distilled water, the resistance of the bioindicators was a little lower than that of those suspended in undiluted blood, but was higher than that of the dried spores with diluted blood. The test results confirm the effectiveness of the method proposed earlier, i.e. to deposit the bioindicators in special test pieces (e.g. tubes or sounds) for the microbiological testing of formaldehyde gas sterilization procedures. These test pieces must be at least as long and as narrow as the longest and narrowest cavity of the object to be sterilized (tubes, catheters). In order to standardize the microbiological testing of formaldehyde gas sterilization procedures and to guarantee a certain minimum efficiency, the bioindicator as well as the test piece and its size (length and inner diameter) should be standardized.(ABSTRACT TRUNCATED AT 400 WORDS)

Culture Media↗
PubMed1983

[Dependency of a microbiological test of a formaldehyde gas sterilization procedure on the shape of objects to be sterilized].

During the last decade, a number of procedures have been developed by different firms for the sterilization of heat-sensitive instruments using a mixture of formaldehyde and water vapor at a temperature of approximately 60 degrees C as means of sterilization. Instruments to be sterilized by this technique as e.g. sounds and catheters normally have long narrow cavities. Therefore, the formaldehyde gas sterilization procedures have to be tested primarily for their capability of achieving a sufficient microbicidal effect within those cavities. For this purpose, the bioindicators are placed into special test pieces. The test pieces commonly in use differ widely in their construction, shape, and size. They mostly consist of some hollow cylinder with an attached capillary or a tube (see Table 1). The authors demonstrated by means of models that the variety of test pieces in use meant that the sterilization procedures had to meet quite different requirements. The models consisted of flexible tubes differing in diameter and length and were connected to short glass tubes. These glass tubes having identical or wider inner diameters than the flexible tubes served as receptacles containing the bioindicators. Spores of Bacillus stearothermophilus served as test organisms. The spores were suspended in defibrinated sheep blood and dried on filter paper. The efficiency of the sterilization technique was measured in terms of the relative number of indicator strips with surviving germs (i.e. non-sterilized indicators) after treatment of the test pieces with the formaldehyde gas. At first, the test results were examined as to their dependency on the length of the flexible tubes. These tubes were 3 mm wide and 5 to 100 cm long, each being sealed at one end and with the bioindicators placed near the sealed end. The percentage of indicators with surviving germs increased with the length of the tubes. After the sterilization process, nearly all indicators (92%) contained in the 1 m tubes proved to be non-sterile (see Table 2). The same results were obtained with tubes open at both ends, with the bioindicators located in the middle section of the tubes (see Table 3). Using tubes of 1 m length, the dependency of the test results on the inner diameter of the test pieces was demonstrated. While all indicators placed into tubes of 3 mm inner diameter still contained surviving germs, those in the tubes of 9 mm inner diameter were all sterile (see Table 4).(ABSTRACT TRUNCATED AT 400 WORDS)

Bacteriological Techniques↗
PubMed1980

[The behaviour of the microflora of wheat related to the cleaning- and the flour mill-flow diagram. IV. Communication: Investigations regarding the behaviour of the microflora during the cleaning and milling of grain (author's transl)].

For the production of certain foodstuffs and preparations of foodstuffs the use of mill products with low microbial germ content is necessary. The demands for microorganisms, in relation to species and number which can be tolerated, depend on the kind of the foodstuff, produced from the milled product. Investigations were done to get milled products with low microbial content; the effect of cleaning and "fractionated" milling of the grain was studied. Flours with a low ash content (flour-type 405 until 550) show generally a low microbial content. More milling-technical problems arise for the production of flours with a high content and a low microbial germ content. The main factors are selection of raw materials, separation of kernels with large-size grains (about 20 till 30%) and an additional surface treatment of the kernels. Whole meal products which are consumed by the customer without preliminary heating, should be also produced from kernels with large size after an intensive surface treatment of the kernels. Food bran should be only produced from grain after a surface treatment. A considerable part of the microflora in the outside layer of the kernels is separated by this particular cleaning method. In the bran from middlings the microflora of the grain concentrates very much. Within the break-passages of the milling diagram a separation should be done in coarse and fine hulls. To improve the demonstrated effects it is necessary to eliminate all the contamination sources during cleaning. The risk of a contamination of milled products with fungi during the milling process is obviously very different. To eliminate this contamination source a detailed analysis is necessary.

Bacteria↗
PubMed1980

[About the identification of sources and routes of mould contamination of bread in large bakeries (author's transl)].

In order to identify sources and routes of the contamination of bread by moulds, the microbial germ content of the air and machine surfaces was investigated in 25 large bakeries of different geographical position and size. On its way from the baking oven to the delivery station, the bread passes through production areas likely to be loaded with more than 90,000 mould spores/cbm air. With a germ content of the air in the bread storage rooms from 85 to 5,000 mould spores per cbm, bread contamination by 10 to 400 mould spores per 100 sq.cm must be expected to take place in the course of one hour. The germ content of the air in bread factories depends, among other factors, on the dust content of the air, the producton processes, the time and type of cleaning as well as on the fresh-air supply system for the production and storage areas. Especially in the bread slicing and packaging areas, a number of production-related sources of microbial spread exist which should be eliminated. The "knife oils" used for the slicing tools are occasionally found to be heavily contaminated with mould and yeast already at their arrival at the bakery. The continuous use of these oils leads to a considerable enrichment with microbial germs.

Bread↗
PubMed1978

[The microflora of sour dough. IV. Communication: bacterial composition of sourdough starters genus Lactobacillus beijerinck (author's transl)].

The bacterial composition of three so called pure culture sourdough starters of varying origin was investigated. 245 isolates were obtained all belonging to the genus Beijerinck. According to their morphological, physiological and biochemical characteristics they were classified into the subgroups: Thermobacterium (L. acidophilus), Streptobacterium (L. casei, L. plantarum, L. farciminis, L. alimentarius) and Betabacterium (L. brevis, L. brevis var. lindneri, L buchneri, L. fermentum, L. fructi vorans). In the three sourdough starters the identified lactic organisms varied in number and proportion. In starter preparation "A" only the varieties L. fructi vorans and L. fermentum were present. Preparation "B" contained a great variety of microorganisms with L. brevis and L. brevis L. lindneri predominating. In starter "C" L. brevis, L. plantarum and L. alimentarius predominated.

Bread↗
PubMed1978

[Application of a new method for the calculation and description of the resistance of microbiological indicators. I. Testing of several common microbiological sterilization indicators (author's transl)].

The method described by SPICHER and PETERS (1975) for the calculation and description of the resistance of microbiological indicators was tested. As test objects served spore-containing earth according to DIN 58946, Attest indicators (3 M Company, Minnesota) and Oxoid Spore Strips (Oxoid Ltd., London). The tests were performed not only for different batches of indicators but also for preparations of different age. After application of steam (120 degrees C), the indicators were examined for the presence of surviving germs capable of multiplication. When plotting the frequency of indicators with surviving germs (q) against the duration of steam action, S-shaped curves were obtained as expected. By altering the scale of the ordinate (y = lg (-ln(1 - q))), the S-shaped curves could be transformed into straight lines. Thus, the experimentally established paired values could be used for a calculation of regression. This method of calculation proved to be suitable in all cases studied. By indicating the position and the slope of these straight regression lines, the resistance of microbiological indicators can be exactly described (cf. Table 2). This method is applicable not only to indicators containing culture spores but also for native spore-containing earth. The indicators examined differed in their resistance and stability. Seven out of eight batches of Attest indicators (cf Figs. 1 and 2 and Table 1) fulfilled the requirements of DIN 58946, Part 4, for the resistance of bio-indicators for steam sterilization. One of the batches had a slightly higher resistance. The Attest indicators tested were of good stability (see Fig. 1 and Table 1). Where surviving germs were present on the indicators after treatment by steam, their growth was recognizable, in 99% of cases, already after incubation of the cultures for 24 hours. Only two batches of Oxoid Spore Strips were available for testing. One batch was of a higher resistance than required by DIN 58946. The second batch was slightly above the lower limit of the permissible range (see Fig. 3). During storage for 12 months, the resistance of both batches was reduced by 3--4 min. Where the indicators exhibited surviving germs after treatment by steam, growth was recognizable in 87% of the cases after incubation for 24 hours, while for the other indicators, incubation for 48 hours was necessary. The experiments confirmed the good stability of native spore-containing earth (see Fig. 5). Within 4--5 years, the steam resistance of the preparations decreased only by 3--4 min.

Bacteriological Techniques↗