PubMed Health⌕ Search

Biomedical subjects

G Spicher

Publications and source records attributed to G Spicher.

At least 19 recordsLinked to original sources
PubMed1991

[The activity of formaldehyde, glutardialdehyde, peracetic acid, chloramine T (N-chlor-4-toluolsulfonamide), m-cresol, ethanol and benzyldimethyldodecylammonium bromide against bacteria which are found in coagulated blood. (Model studies for chemical disinfection of instruments].

The experiments were performed using frosted glass as carrier with its surface being contaminated with whole blood containing Staphylococcus aureus as test organism. At the time of sampling, a heparin preparation was added to the blood to prevent premature coagulation. After addition of the staphylococci, coagulation was initiated by means of a heparin antagonist. 10, 25, 50, 100, and 150 microliters, respectively, of the blood were homogeneously spread on rectangular test areas of 10 x 20 mm. After the blood had coagulated, each of the test objects was placed in 15 ml of the solution (20 degrees C) containing the active ingredient tested for 60 min. After that, the test objects were removed from the disinfectant and, in order to inactivate any adhering active components, treated with a neutralizing solution of suitable composition. The number of viable germs (colony-forming units) was determined quantitatively. The blood samples were ground together with quartz sand. Aliquots of the diluted suspensions were mixed with molten agar medium. The plates then were incubated at 37 degrees C over a period of 14 days. The relative number of viable germs (N/No) per test object was calculated from the number of colonies. Plotting of the microbicidal effects obtained (log N/No] versus the concentration of the active substance (see Figs. 1-3) yielded curves differing in some characteristics as e.g. curvature, slope of the lower curve section (log N/No). less than -3), concentration range according to the layer thickness of the contamination. To visualize the reduction of the efficacy of the respective disinfectants caused by blood, the concentrations of active components were determined which are necessary to achieve a microbicidal effect of log (N/No) = -4. These concentrations were plotted versus the amounts of blood per test area (Fig. 4). The resulting curve for formaldehyde was slightly U-shaped. With a raising amount of blood, the concentration required slightly decreased in the beginning and increased again from an amount of ca. 100 microliter blood per test area. For all other active substances, the required concentration of these substances increased with the amount of blood used. The curve obtained for ethanol exhibited the lowest slope. The slope of the curves increased in the following order: ethanol, m-cresol, peracetic acid, chloramine T, glutardialdehyde, benzyldimethyldodecylammoniumbromide. The curves for chloramine T and glutardialdehyde nearly paralleled each other.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

[A simple apparatus for the determination of the resistance of bioindicators to saturated steam at temperatures less than 100 degrees C., tested with Enterococcus faecium as test microbe].

An apparatus is described by means of which the resistance of microbiological indicators to water vapor at temperatures below 100 degrees C can be determined. The apparatus can be assembled from parts generally available in laboratories. The principle of the apparatus consists in the production of water vapor of the desired temperature under conditions of reduced pressure and its recondensation to water after having passed a special chamber. Accordingly, the device consists of a heated round-bottom flask serving as steam generator, an exposure chamber (B), and a condenser (D) attached to a receiver (E). The bioindicators are exposed to the water vapor in the exposure chamber. A bypass located between the steam generator and the condenser allows for continuous operation even when the exposure chamber is opened. The reduced pressure was achieved by means of a waterjet pump and adjusted by two tandem-joined pressure-regulating valves as needed. The apparatus was tested using water vapor of 73, 75 and 77 degrees C, respectively, and bioindicators containing Enterococcus faecium as test organism. In the range of exposure periods in which bioindicators change from the status "all indicators having surviving test organisms" to the status "all indicators free from surviving test organisms" the bioindicators showed D values of 5.7, 4.4 and 2.9 min, respectively. For the temperature dependence of resistance a z value of 12.5 Kelvin resulted.

Disinfection↗
PubMed1988

[The significance of heat activation for the testing of bioindicators on surviving microorganisms exposed to formaldehyde].

Heat activation is a special phenomenon: After an additional heat treatment, a larger share of the bacterial spores which had been exposed to formaldehyde proves to be viable than without such heat activation. Model studies have been performed to test the effects of heat activation on the examination of bioindicators and test objects for surviving organisms. Test objects (cotton threads of 1 cm length) contaminated with spores of Bacillus stearothermophilus were used for these trials. The test objects were exposed to a 2% formaldehyde solution at 60 degrees C. After periods of action of 30, 45, 60 ... and 105 min, formaldehyde adhering to the test objects was neutralized. For testing these objects for surviving organisms, they were placed into a nutrient medium and incubated for 40 days at 56 degrees C. The investigation consisted of 2 parallel test series which only differed in one single point. In one series, the test objects were incubated at 56 degrees C as soon as they had been placed into the nutrient solution. In the other series, the test objects were exposed to a temperature of 95 degrees C for 1 h (heat activation) before starting incubation. The culture tubes were checked daily to see whether signs of growth (turbidity and deposits) could be observed. The frequencies of test objects with surviving organisms depending on the period of action of formaldehyde and the period of incubation determined in this way are based on the examination of 72 test objects each. Without heat activation, the share of test objects on which surviving test organisms could be detected, increased slowly with the period of incubation. Only after 30 days the counts did not increase any more when continuing the incubation (cf. Fig. 1). In the test series in which the spores had been subjected to heat activation before the incubation period, useful results were obtained already after 3 days. They only changed slightly when incubation was continued. Moreover, the frequency of test objects on which surviving organisms could be detected was always considerably higher than without heat activation. When the frequency of test objects with surviving organisms was plotted against the period of action of formaldehyde (cf. Fig. 2A), S-shaped curves resulted.(ABSTRACT TRUNCATED AT 400 WORDS)

Formaldehyde↗
PubMed1988

Biological indicators and monitoring systems for validation and cycle control of sterilization processes.

The article is divided in four parts. The first part deals with terms and definitions. After that there is given a description of the most common types of biological indicators. These two parts furnish material and introduce to the third part, a survey of the components of monitors, their functions and the criteria one has to take into consideration when designing them. The fourth and last part deals with the most essential feature of biological indicators, the resistance, its calibration, description and adjustment.

Quality Control↗
PubMed1987

[Dependence of microbiologic test results of formaldehyde gas sterilization methods on the nature of the test material].

The efficiency of a formaldehyde gas sterilization procedure was evaluated with the aid of test pieces consisting of various materials. Both rigid and flexible tubes served as test pieces. The tubes were 75 cm long with an inner diameter of 1 mm and were sealed at one end. The bioindicators were placed inside the tubes close to the sealed end. Dried spores of Bacillus stearothermophilus adhering to linen threads served as test organisms. The test results varied according to the material of the test pieces and the thickness of their walls (see Table 1). In flexible tubes made of silicon rubber, all bioindicators became sterile, in tubes of stainless steel, all bioindicators exhibited test organisms that had survived. The findings for materials such as polyvinyl chloride, polyethylene, polyamide and polytetrafluorethylene ranged between these two extremes; the frequencies of bioindicators containing viable germs were 10, 55, 68 and 85%, respectively. Rigid and flexible tubes which had been sealed at both ends served to demonstrate that silicon rubber and polyvinyl chloride were highly permeable for formaldehyde and water vapour. Also the other plastic materials tested were permeable for formaldehyde and water vapour but longer exposure periods were needed to create conditions in the interior of the tubes that would result in a killing of the test organisms (see Fig 2). In this respect, polyamide exhibited a peculiar behaviour. The number of viable spores remained at the initial level for a long period before a decline took place. From the results of testing, it is concluded that test pieces must conform to the objects to be sterilized not only in their dimensions (length, inner diameter) but also in the characteristics of their material. The walls of the test pieces should not have a higher permeability for formaldehyde and water vapour than the material to be sterilized. The highest demands on the efficiency of formaldehyde gas sterilization procedures are those created by mental tubes and thick-walled flexible polytetrafluorethylene. Instruments and devices to be sterilized by a formaldehyde gas procedure should be preferentially made of materials which are sufficiently permeable for formaldehyde and water vapour as e.g. silicon rubber. Such gas-permeable components may considerably facilitate the sterilization of cavities which have a small lumen and are difficult to reach.

Chromium↗
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↗
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↗
PubMed1978

[Some aspects relating to the aflatoxin generation during the self-heating of cereals].

In a stored batch of grain which was already affected by mould-formation tests were carried out with the known aflatoxin producer Aspergillus flavus. A significantly lower aflatoxin production ensued if the mould growth was not connected with self-heating of the stored product. However, in conformity with increasing mould formation the germinating power was adversely affected and the significant signs (fatty acid number, reductive and none-reductive sugars) were influenced in the grain, irrelevently whether or not this led to self-heating. It appears obvious that as the self-heating increases in the stored product, the optimal temperature range favourable for the Aspergillus flavus is rapidly exceeding and this caused restriction to the aflatoxin formation. This leads to the conclusion that the contamination on the outer layer by mycotoxines is more significant on the outer layers than the more or less strong mould formation in the interior (so-called-mouldly pockets) which ensued through the self-heating fenomena.

Aflatoxins↗
PubMed1976

[Microbial resistance to formaldehyde. I. Comparative quantitative studies in some selected species of vegetative bacteria, bacterial spores, fungi, bacteriophages and viruses].

The resistence of different microorganisms to formaldehyde was determined. As test objects served gram-negative and gram-positive vegetative germs (Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella paratyphi-B, Staphylococcus aureus, Streptococcus faecalis), bacterial spores (Bacillus cereus, Bacillus pumilus, Bacillus stearothermophilus, Bacillus subtilis), fungi (Aspergillus niger, Candida albicans), bacteriophages (Escherichia coli phages, T1, T2, T3), and viruses (adenovirus, poliomyelitis virus, vaccinia virus). For the studies, suspensions of germs were exposed at identical temperature (20 degrees C) and pH (7.0). The microbicidal effect of formaldehyde was measured by the decrease of the proportion of germs capable of multiplication in the suspension (lg (N/N0); where: N0 equals initial number of germs capable of multiplication; N equals number of germs capable of multiplication after exposure to formaldehyde). For all germs the dependence of the microbicidal effect on the concentration of formaldehyde was determined. In all experiments, the duration of exposure was two hours. Pseudomonas aeruginosa, Klebsiella pneumoniae, and Salmonella paratyphi-B were found to be more susceptible than Staphylococcus aureus (vf. Fig. 1 A). The strains of Pseudomonas aeruginosa used were widely varying as to their susceptibility. To obtain equal microbicidal effects, concentrations of formaldehyde almost three times as high had to be used for the most resistant strain than were necessary for the most susceptible strain of Pseudomonas aeruginosa. All strains of Klebsiella pneumoniae examined were found to have an identical resistence to formaldehyde. Streptococcus faecalis was even more resistant to formaldehyde than Staphylococcus aureus. In the case of Streptococcus faecalis, a concentration of formaldehyde about three times as high had to be used to obtain microbicidal effects of identical magnitude. For the killing of Candida albicans cells concentrations of formaldehyde not higher than those needed for the killing of vegetative gram-negative bacteria were necessary. The conidia of Aspergillus niger were found to be more resistant than the cells of Candida albicans but did not require any higher concentrations than for the killing of Staphylococcus aureus (see Fig. 1 B). In the case of bacterial spores, a special phenomenon was observed. If the spores had been exposed to a temperature of 80 and 95 degrees C, respectively (depending on the species involved) for one or two hours following exposure to formaldehyde, a considerably higher number of spores was found to be capable of germination and colony formation than without such treatment (heat activation: cf. Fig. 2A and Fig. 2B). The spores of Bacillus cereus had only a relatively low resistance to formaldehyde. To reduce the proportion of the spores capable of colony formation to 1/10000, a 2.9% formaldehyde concentration was necessary without heat activation and one of 10.8% with heat activation...

Adenoviridae↗
PubMed1976

[Test for the efficacy of disinfectants at surfaces in test models. I. (communication:) Dependence of experimental results on the method of demonstration of surviving germs (swab and rinsing) (author's transl)].

For the testing of disinfectants at surfaces, the germs having survived at the surface are demonstrated by means of swabs according to the guide-lines of the Deutsche Gesellschaft fur Hygiene und Mikrobiologie (DGHM): after the period of exposure to the disinfectant, the surfaces were rubbed off with a damp swab, and the frictional surface of the swab was plated out on nutrient agar. The effectiveness of this technique was compared with the effectiveness of a rinsing method in a test model. In the rinsing process, the objects to be tested for surviving germs were shaken together with a suspension and with glass beads. Then the content of germs in the suspension was quantitatively determined by means of dilution tests and pour plates. The findings were evaluated according to the guide-lines for evaluation of the DGHM (less than or equal to 10 surviving germs = adequate efficacy). For the findings obtained by rinsing, the average number of surviving germs was also determined. For maldehyde solutions were used as disinfectants for the test models (time of exposure: 4 hours; temperature 22 to 25 degrees C). These disinfecting experiments were performed on raw smoothed as well as on varnished beech-wood. The experimental results showed that the criterion "less than or equal to X surviving germs" in itself does not mean clear evidence of the efficacy of a disinfectant. The one and only decisive criterion is the frequency of the statement that a certain disinfectant or a corresponding dilution of this disinfectant has shown adequate efficacy. Therefore, one single test according to the guide-lines of the DGHM is insufficient. The frequency of the finding "adequate efficacy" is not only dependent on the concentration of the disinfectant but also on the technique used for the demonstration of surviving germs. The swab method (according to the guide-lines of the DGHM) occasionally resulted in the finding "adequate efficacy" already if 10(4) to 10(5) surviving germs were demonstrable by the rinsing method. The range of formaldehyde concentrations for which the finding of adequate efficacy were present with a frequency between 20% (minimum) and 80% (maximum) amounted to 0.2-0.5% (varnished surface) and 1.1-2.5% (raw surface), respectively for the swab method. The respective figures for the rinsing method were 0.8-1.3% and 4.8-6.5%, respectively. When using the swab method, there is a slower increase in the efficacy of the disinfectant with concentration as compared with the rinsing method. The rinsing method is, therefore, more representative of the efficacy of a disinfectant than the swab method. On account of the results of this study, it is recommended for model experiments to recover the surviving germs quantitatively by the rinsing method and to determine their number.

Disinfectants↗
PubMed1975

Experiments on terminal disinfection by formaldehyde vapor in the case of smallpox.

The usually recommended terminal disinfection by formaldehyde vapor is unable to completely inactivate vaccinia viruses embedded in scabs. In view of our results, we recommend doubling the concentration of formaldehyde (10 g of formaldehyde per m3 of space) and prolonging the time of exposure to 24 h for terminal disinfection in the case of smallpox. Subsequent disinfection by scrubbing assumes special importance, since no complete inactivation of the scabs occurs.

Animals↗
PubMed1975

[Quantitative description of the resistance of microbiological indicators by means of characteristic data (author's transl)].

The ambiguity of the quantitative description of the resistance of microbiological indicators by means of the terms common thus far, namely "resistance" (maximal period of action after which all indicators still exhibit organisms capable of reproduction) and "death time" (minimal period of action after which organisms capable of reproduction cannot be demonstrated any more in any of the indicators) is shown. Among other factors, the probability that all indicators will yield identical findings (sterility or growth of surviving organisms) at a defined time, is dependent upon the number of indicators in each case. The more indicators are tested, the lower "resistance" and the later the "death time" will be. Instead of times when all indicators present an identical reaction, times (or values related to these times in a defined way) should be taken at which indicators show the absence of organisms or the presence of surviving ones with a defined frequency. There is a defined relationship between the frequency of indicators found free from (resp. containing) surviving organisms and the number of surviving organisms per indicator (cf. Figs. 1 and 2). If the regularity of the decrease of organisms with the period of action of the destroying agent is known, 2 values are sufficient for a clear description of the resistance of a preparation of microbiological indicators. As characteristic values those values of action are proposed after which 99% and 1% of indicators will exhibit surviving organisms (t99% and t1%, respectively). The period during which the dependence of the frequency of presence of sterile indicators (po) upon the period of action of the destroying agent may be determined with sufficient precision and at justifiable experimental expenditure, is corresponding to a decrease of surviving organisms to appr. 1/30. From practical experience, it will be justified in the preponderant majority of cases to assume a logarithmic orderof death as given. Under such conditions, there will be a clear relationship between lg(-ln po) and the period of action of the destroying agent, so that test results may be easily evaluated by means of a simple graphical method or regression calculation. Graphical (FIG. 3) and mathematical determination of characteristic values from the frequency of indicators exhibitoring surviving organisms in the destruction test, after different periods of action, is explained by means of an example (Fig. 3; Tables 2 and 3) and a calculation (Table 1). To keep variation of experimental results sufficiently low, at least 30 (if possible 50) indicators per period of action should be studied for surviving organisms (cf. Fig 4). When evaluating results, different weights of the individual values and their asymmetric distribution around a maximum at t80% (Fig 5) should be taken into consideration.

Bacteriological Techniques↗