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Biomedical subjects

G Spicher

Publications and source records attributed to G Spicher.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1975

[Sterility control: basic mathematical considerations (author's transl)].

The subject of control of sterility in homogenous lots by means of random sampling is discussed. The probability that non-sterile lots may be declared as accepted, was calculated by means of hypergeometric, binomial, and Poisson distribution. The following factors were considered: size of samples, size of lots, and degree of contamination of lots. The values obtained were reproduced in graphs (Figs. 1, 2, and 4). Reference is made to the conditions that have to be met in each case to enable a use of the various distribution functions for a calculation of the acceptance probability of non-sterile lots (Table 1). Furthermore, the necessary size of samples to contain at least one contaminated unit was calculated by means of binomial distribution for probabilities of 90, 95, and 99% (Fig. 3). For example, from a lot having a degree of contamination of 10%, 30 units would have to be assayed for sterility to recognize non-sterility of such a lot in 95% of cases. A degree of contamination of 1% would reguire already 300 units to be examined...

Mathematics↗
PubMed1975

[The problem of the measurement of relative humidity in the disinfecting dryceaning process (author's transl)].

One of the most important conditions for obtaining reproducible microbiological results by disinfecting drycleaning is a control of the relative humidity of the drycleaning bath. An apparatus called "Wasserkontroller" (see Fig. 1) had been recommended as a device for the determination of the relative humidity. It consists of a special cylindrical casing into which the sensor of a hair hygrometer has been introduced. In contrast to electric instruments, this apparatus has the advantages of rigidity, simple adjustment, and above all of a low cost price. In practice, however, the "Wasserkontroller" proved to be a failure, since it indicated false values at times. In the studies published and discussed in the present paper, the causes for the malfunction of the hair hygrometer, in the device mentioned were determined. It could be observed that a malfunction of the hair hygrometer mainly occurred when the hairs fixed in the sensor were moistened by the drycleaning bath or by the drycleaning solvent (perchloroethylene), respectively. Then the hair hygrometer is no longer capable of reacting sufficiently to the fluctuation of the relative humidity of the bath. On the basis of the experimental results obtained instructions are given for the employment of hair hygrometers in drycleaning and for the design of the device casing: 1. The hair hygrometer has to be protected inside the device casing against a contamination by the bath or the condensing drycleaning solvent. 2. The inlet pipes to the device casing and the casing itself have to be protected against loss of heat as well as against the influence of heat sources. Temperatures of drycleaning bath and device should be balanced. 3. The inlet pipes to the device should be provided with a flowmeter or a flow detector, respectively. 4. The outlets of the device should be connected directly with the drum filled with the drycleaning bath. 5. The device has to be constructed in such a way that no infiltrated air may be sucked in. 6. The hair hygrometer has to be cleaned and to be adjusted at suitable time intervals. Provided that the technical requirements are met, hair hygrometers may also be considered as reliable measuring instruments in the practice of drycleaning.

Clothing↗