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Biomedical subjects

K F Weiss

Publications and source records attributed to K F Weiss.

12 recordsLinked to original sources
PubMed1986

Microbiological quality of bottled water sold in Canada.

The microbiological quality of bottled water sold in Canada was evaluated. A total of 114 lots of bottled water, both domestic and imported, were analyzed for aerobic colony count, coliforms, fecal coliforms, and Escherichia coli. No fecal coliforms or E. coli were found. Nineteen (46%) of the 41 lots of domestic purified water were found to exceed aerobic colony count standards and another lot exceeded coliform standards. One lot each of domestic and imported mineral water exceeded coliform standards. If mineral water were governed by the aerobic colony count standards for bottled water, then five lots each of both domestic and imported mineral water would have been found to be unsatisfactory. More surveillance of the bottled water industry in Canada is recommended.

Canada↗
PubMed1971

Identification of enterotoxin E.

Identification of a new enterotoxin was accomplished by purification of the enterotoxin produced by staphylococcal strain FRI-326 and by preparation of specific antitoxin to the enterotoxin. Toxicity of the preparations was determined in rhesus monkeys, and specificity of the enterotoxin-antitoxin reaction was determined in gel diffusion plates. The enterotoxin was designated enterotoxin E.

Animals↗
PubMed1970

Relationship between staphylococcal antiserum titer and zone development on immune serum plates.

A workable relationship was established between the standard serum titers of staphylococcal immune antisera and the development of precipitin zones on serum agar around colonies of staphylococcal strains producing homologous antigens (enterotoxins). The standard titer of a serum is defined as the reciprocal of that serum dilution which, with 10 mug of pure enterotoxin per ml, will give a precipitin zone 10 mm in length in single gel-diffusion tubes after 7 days of incubation at 25 C. A numerical scale was set up for determining the intensity of precipitin zones on serum agar. A reading of 3 was considered optimum. This correlated well with a standard serum titer of 25, when 1 ml of such a serum was used per 20 ml of medium per serum plate. From this relationship, the minimum volume of serum required to give optimum precipitin zone development can be calculated.

Agar↗
PubMed1969

Production of staphylococcal enterotoxins A, B, and C in various media.

The effect of initial pH and of length of incubation time at 37 C in four different growth media on the production of staphylococcal enterotoxins A, B, and C was determined. A starting pH of 6.8 gave higher yields of enterotoxins B and C than either pH 6.0 or 5.3. The production of enterotoxin A was, however, not materially affected by the low initial pH of 5.3. Prolonged incubation (48 to 72 hr) resulted only occasionally in higher yields of enterotoxin. The effect of the media on the amount of enterotoxin produced is considerable. Difco Brain Heart Infusion (BHI) was inferior to either Fisher BHI, 4% NZ Amine (NAK), or 3% NAK plus 3% protein hydrolysate powder at the three initial pH values, regardless of length of incubation time. The slight effect of the low starting pH on the production of enterotoxin A is being further investigated.

Culture Media↗
PubMed1967

Some properties of heat-resistant and heat-sensitive strains of Clostridium perfringens. I. Heat resistance and toxigenicity.

Heat resistance at 100 C (D-values), sporulating ratios, toxigenicity for mice, and lecithinase activity (as micrograms per milliliter of enzyme, ascertained by the lecithovitellin reaction) were determined for four strains of Clostridium perfringens. A definite inverse relationship between thermal resistance and toxigenicity was found. The D-values ranged from 17.6 for the most heat-resistant strain to 0.3 for the strain possessing the least heat resistance, with corresponding lecithinase activities from 25 to 133 mug/ml of enzyme. The sporulating ratios did not differ greatly between the strains. The heat stability of the toxin was greater at 100 C than at 75 C. There was a noticeable difference between the heat stabilities of the toxin in the culture fluids of the heat-sensitive and heat-resistant strains at pH 7.0 when the toxic filtrates were held at 100 C. At a holding temperature of 75 C, a similar but lesser difference was observed at pH 5.5. Heat resistance and lecithinase activity did not change when a substrain of the least heat-resistant parent strain was obtained through heat selection by a single transfer, or when the most heat-resistant strain was transferred serially 12 times.

Animals↗
PubMed1966

Mice and monkeys as assay animals for Clostridium perfringens food poisoning.

Spores and vegetative cells of Clostridium perfringens, in combination with meat or starch paste, sterile culture filtrates, lecithinase, and phosphorylcholine, were administered to mice and rhesus monkeys in an attempt both to evaluate the animals as test agents and, if possible, to elucidate the active factors producing food-poisoning symptoms caused by this organsim. Some of the preparations were administered to the monkeys by stomach tube; others, in gelatin capsules which were treated with formaldehyde so that the release of their contents was delayed and presumably reached the intestines of the animals. Any changes in intestinal passage times and in consistency of stools of the animals were observed, and the counts of C. perfringens in the feces of the monkeys previous and subsequent to treatment were recorded. The results obtained were inconclusive. Diarrhea occurred only relatively infrequently in both species, regardless of the substance fed or the mode of administration. The changes in intestinal passage times were not great, although in the monkeys there appeared to be a slight trend toward reduction as the magnitude of the bacterial load increased. Phosphorylcholine appeared to have little, if any, effect in reducing intestinal passage time of mice or monkeys. No procedures explored in these experiments could be said to be satisfactory as a means of animal assay for food poisoning strains of C. perfringens since typical symptoms did not appear with regularity.

Animals↗
PubMed1965

Inhibitory action of selenite on Escherichia coli, Proteus vulgaris, and Salmonella thompson.

Weiss, K. F. (Iowa State University, Ames), J. C. Ayres, and A. A. Kraft. Inhibitory action of selenite on Escherichia coli, Proteus vulgaris, and Salmonella thompson. J. Bacteriol. 90:857-862. 1965.-The resistance of three microorganisms, Escherichia coli (ISU-41), Proteus vulgaris (ISU-37c), and Salmonella thompson (ISU-86-2), to increasing concentrations of selenite was determined. E. coli was completely inhibited by 1.25% sodium hydrogen selenite, and 0.25% sodium hydrogen selenite caused a pronounced lag. P. vulgaris survived selenite concentrations of over 3%. S. thompson was inhibited completely by 3% selenite but not by 2.5%, although there was a considerable lag and a decrease in total growth. The relationship of growth, uptake, and reduction of selenite was determined. The susceptible E. coli incorporated up to twice as much selenium as did the other two organisms during the early stages of incubation. Radioautographs of seleno analogues of sulfur-containing amino acids revealed the presence of seleno-cystine in all three organisms, and seleno-methionine in E. coli. Compounds having R(F) values corresponding to possible oxidation products of seleno-methionine were present in the hydrolysates of P. vulgaris and S. thompson. Kinetic aspects of selenite uptake, rather than the ultimate localization of selenite in the cell protein, appear to be the factors that determine the degree of resistance or of susceptibility to selenite.

Bacterial Proteins↗