Search PubMed⌕ Search

Biomedical subjects

E H Marth

Publications and source records attributed to E H Marth.

At least 37 records · Page 2Linked to original sources
PubMed1989

Growth and production of enterotoxin A by Staphylococcus aureus in cream.

Behavior of Staphylococcus aureus strains 100-A, 196-E, 254, 473, 505, and 521 in sweet (18 to 80% milk fat) and neutralized sour cream was studied. Cream was inoculated to contain approximately 10(3) to 10(4) S. aureus/ml, depending on milk fat content, and was incubated at 4, 22, or 37 degrees C. Determinations were made of aerobic plate count, S. aureus count, and pH. When growth in cream exceeded 10(7) S. aureus/ml, enterotoxin analysis was done. Sweet and neutralized sour cream supported growth of all strains of S. aureus tested. Strains 100-A, 196-E, 473, 505, and 521 grew sufficiently to produce enterotoxin in sweet cream of 18 or 32% milk fat held at 37 degrees C for 18 h or at 22 degrees C for 52 h. Populations of strains 100-A, 196-E, 505, and 521 exceeded 10(6) cells/ml in sweet cream of 36% milk fat held for 18 h at 37 degrees C. Strains 100-A and 521 grew to more than 10(6) cells/ml in sweet cream of 40% milk fat held for 18 h at 37 degrees C. No strain of S. aureus grew to levels associated with detectable enterotoxin production at 4 degrees C within 14 d in any cream. Incubation temperature, milk fat content of cream, and variation among strains influenced the ability of S. aureus to grow and produce enterotoxin.

Aerobiosis↗
PubMed1989

Fate of Staphylococcus aureus in whey, whey cream, and whey cream butter.

Fresh Cheddar cheese whey was inoculated with ca. 10(6) Staphylococcus aureus/ml and held at 4, 25, and 37 degrees C for 48 h. Numbers of staphylococci decreased in whey at 25 and 37 degrees C and decreased or remained constant in whey at 4 degrees C. When Cheddar cheese whey was neutralized with sodium hydroxide before inoculation with ca. 10(2) or 10(6) S. aureus/ml, numbers of the bacterium increased at all incubation temperatures. Viability of S. aureus strains in whey butter made from inoculated whey cream (from Cheddar cheese whey) was determined. Whey cream was either neutralized to a titratable acidity of .15% or untreated before inoculation with ca. 10(4) S. aureus/ml. Butter churned from the whey cream was held at 4, 25, and 30 degrees C for up to 4 wk. Viability of S. aureus was enhanced in lightly salted (1%) whey cream butter and in butter made from neutralized whey cream. Strains of S. aureus did not survive in unsalted or in salted (1.5%) butter made from untreated whey cream.

Animals↗
PubMed1989

"New" food-borne pathogens of public health significance.

Recent work by epidemiologists and microbiologists has uncovered several hitherto unrecognized food-borne bacterial pathogens of public health significance. One of these, Listeria monocytogenes, has attracted considerable attention because of two major cheese-related outbreaks of listeriosis that were characterized by cases of meningitis, abortion, and perinatal septicemia. Thus far, L. monocytogenes has been responsible for well over 300 reported cases of food-borne listeriosis, including about 100 deaths, and has cost the dairy industry alone more than 66 million dollars as a result of product recalls. The ability of L. monocytogenes to grow at refrigeration temperatures, coupled with appearance of the pathogen in raw and processed meats, as well as poultry, vegetables, and seafood, makes this bacterium a serious threat to susceptible consumers and to the entire food industry. Yersinia enterocolitica, another psychrotrophic food-borne pathogen of recent concern, was linked to several outbreaks of yersiniosis associated with consumption of both raw and pasteurized milk, as well as contaminated water. Food-borne infections involving Y. enterocolitica typically result in enterocolitis, which may be mistaken for acute appendicitis. Unfortunately, inadvertent removal of healthy appendixes from victims of food-borne yersiniosis is all too common. Although known for many years, Campylobacter jejuni has only recently been recognized as a food-borne pathogen and a leading cause of gastroenteritis in the United States. Notable outbreaks of campylobacteriosis linked to consumption of raw milk, cake icing, eggs, poultry, and beef have underscored the need for thorough cooking and proper handling of raw products.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Food additives and plant components control growth and aflatoxin production by toxigenic aspergilli: a review.

Growth and aflatoxin production by toxigenic aspergilli are partially or completely inhibited by the undissociated form of acetic, benzoic, citric, lactic, propionic and sorbic acids. Salts such as sodium chloride, potassium chloride and sodium nitrate, at low concentrations, can enhance aflatoxin production. At higher concentrations they become inhibitory, but marked inhibition requires amounts of the salts greater than are commonly used in foods. Phenolic antioxidants, sometimes added to foods to prevent oxidative deterioration, also are inhibitory to toxigenic aspergilli. Other inhibitory agents include certain insecticides, methylxanthines (caffeine and theophyllin), and components of some herbs, spices and other plants.

Aflatoxins↗
PubMed1988

Growth and aflatoxin production by Aspergillus parasiticus in a medium at different pH values and with or without pimaricin.

A glucose-yeast extract-salt medium containing 0, 5, 7.5, 10, 15 or 20 micrograms pimaricin/ml with an initial pH of 3.5 or 5.5 was inoculated with Aspergillus parasiticus WB 108 and incubated at 15 degrees or 28 degrees C. The pH, weight of mycelium and amount of aflatoxin produced were determined after 3, 7, and 10 days and after 14, 21, and 30 days when incubation was at 28 degrees or 15 degrees C, respectively. Increasing the concentration of pimaricin in the medium with an initial pH of 5.5 decreased the amounts of aflatoxin B1 and G1 produced after 3 days of incubation. When the initial pH of the medium was 3.5, no growth or toxin production occurred after 3 days of incubation in the medium containing 7.5 micrograms or more of pimaricin/ml. The presence of 20 micrograms of pimaricin/ml inhibited growth and toxin production after 7 days of incubation. When cultures were incubated at 15 degrees C, there was a lag phase which extended from 9 to 16 days, and the amounts of aflatoxin produced decreased with an increasing concentration of pimaricin. Pimaricin did not completely inhibit the growth and aflatoxin production by A. parasiticus. Pimaricin, in combination with a low pH, low temperature or 4% or 6% NaCl, initially caused slow mycelial growth and low toxin production, but the mold overcame the inhibitory effects and produced substantial amounts of mycelium and toxin.

Aflatoxins↗
PubMed1988

Methods for improved recovery of Listeria monocytogenes from cheese.

Method of homogenization (Waring blender versus stomacher), type of diluent (tryptose broth [TB] versus aqueous 2% trisodium citrate), and temperature of diluent (20 versus 40 degrees C) were compared for recovery of Listeria monocytogenes from freshly made and ripened Colby cheese. By using direct plating on McBride listeria agar, significantly higher numbers of L. monocytogenes were recovered when cheese samples were (i) homogenized for 2 min with the blender rather than the stomacher (P less than 0.01), (ii) diluted in trisodium citrate rather than TB (P less than 0.01), and (iii) diluted in diluents at 40 rather than 20 degrees C (P less than 0.05). Based on these results, a new diluent/enrichment medium was developed by adding 2% trisodium citrate to TB (TBC). Despite superior results with the blender, biosafety concerns led to use of the stomacher for homogenization of cheese samples; hence, the stomaching time was increased to 3 min. Results obtained by direct plating indicated that recovery of L. monocytogenes from Colby cheese and from curd samples taken during manufacture of brick cheese increased when samples were diluted 1:10 in TBC at 45 degrees C and stomached for 3 min, as compared with similarly treated samples diluted in TB at 25 degrees C. A similar comparison of both diluents for recovery of L. monocytogenes from cold-pack cheese food yielded bacterial counts which were not significantly different. Recovery of L. monocytogenes from cold-enriched (at 4 degrees C for up to 8 weeks) samples of Colby cheese and cold-pack cheese food was generally similar for samples homogenized in TBC or TB.

Animals↗
PubMed1988

Growth of Listeria monocytogenes at different pH values in uncultured whey or whey cultured with Penicillium camemberti.

Wheys from making Camembert cheese were either uncultured or cultured with Penicillium camemberti, adjusted to pH 5.0, 5.2, 5.4, 5.6, 6.2, and 6.8, and filter sterilized. Whey samples were inoculated to contain 100 to 500 Listeria monocytogenes (strains Scott A, V7, CA, or OH) cfu/mL and incubated at 6 degrees C. Counts of L. monocytogenes were obtained by surface plating appropriate dilutions on Tryptose Agar. Listeria monocytogenes failed to grow at or below pH 5.4; except for strains Scott A and OH which grew in cultured whey at pH 5.4 and attained populations of 7.8 x 10(3) and 5.4 x 10(4) cfu/mL, respectively, after 35 d of storage. In uncultured whey at pH 5.6, 6.2, and 6.8, populations of L. monocytogenes increased from 7.20 to 7.81, 7.51 to 8.23, and 7.48 to 8.08 log10 cfu/mL, respectively, after 35 d of storage at 6 degrees C. In cultured whey at pH 5.6, 6.2, and 6.8, numbers of L. monocytogenes increased from 7.53 to 8.13, 7.82 to 8.55, and 7.95 to 8.80 log10 cfu/mL, respectively, after 35 d of storage. Generation times for L. monocytogenes at 6 degrees C in uncultured whey at pH 5.6, 6.2, and 6.8 ranged between 25.3 and 31.6 h, 14.8 and 21.1 h, and 14.0 and 19.4 h, respectively, depending on the Listeria strain. In contrast, generation times were significantly (p less than 0.05) shorter in cultured whey and ranged between 16.6 and 27.4 h, 10.3 and 16.6 h, and 17.4 and 16.3 h at pH values of 5.6, 6.2, and 6.8, respectively.

Cheese↗
PubMed1986

Use of ultraviolet energy to degrade aflatoxin M1 in raw or heated milk with and without added peroxide.

Raw whole milk was artificially contaminated to contain 1 ppb aflatoxin M1. A thin layer of milk (.1 cm) was irradiated with ultraviolet energy. In the first experiment, milk was held at 90 degrees C for 10 min, cooled to 20 degrees C, and irradiated for 30 min. Amount of aflatoxin M1 decreased equally (56.2 vs. 53.9%) in raw or preheated milk, suggesting no involvement of milk enzymes in degrading aflatoxin M1 by ultraviolet energy. Data obtained when raw milk containing aflatoxin M1 was exposed to ultraviolet energy for 15 to 60 min suggest first order kinetics for the degradation reaction. In another experiment, milk was held at 5, 25, or 65 degrees C while it was being irradiated. Aflatoxin M1 was degraded at all temperatures. Amount of toxin decreased nonlinearly when temperature at which milk was held was increased. Presence in milk of benzoyl peroxide at .002% did not change the extent to which aflatoxin M1 was degraded by irradiation. Amount of toxin, however, decreased by 89.1% in milk containing .05% H2O2 as compared with 60.7% for H2O2-free milk when both were exposed to ultraviolet irradiation for 20 min at 25 degrees C.

Aflatoxin M1↗
PubMed1985

Evaluation of 1,3-pentadiene for mutagenicity by the Salmonella/mammalian microsome assay.

1,3-Pentadiene, a food contaminant produced by some molds when they metabolize sorbic acid, was tested for mutagenicity, using variations of the Salmonella/mammalian microsome assay. The chemical was incorporated into the test system (with and without S9 mix) by 3 methods: (a) the standard plate incorporation assay, (b) a liquid preincubation procedure and (c) exposure of test bacteria in the soft agar overlay to gaseous 1,3-pentadiene. The chemical was extremely toxic to the test bacteria with amounts as low as 2.0 microgram/plate causing cell death. However, none of the nonlethal concentrations tested by any of the methods was mutagenic to Salmonella typhimurium strains TA97, TA98, TA100, TA1535, TA1537 or TA1538.

Alkadienes↗
PubMed1982

Association of aflatoxin M1 with casein.

Equilibrium dialysis was used to determine whether aflatoxin M1 (AFM1) binds to casein. Simulated milk ultrafiltrate (SMUF) containing 10 or 20 ng/ml of AFM1 was dialyzed against SMUF containing casein micelles. After 24 h at 7 degrees C, the casein suspension contained 2.5- or 2.9-fold, respectively, more toxin than that found in SMUF. An average of 17.9 or 55.3 micrograms of AFM1, respectively, per gram of casein was bound. In a separate experiment, milk naturally contaminated with AFM1 was treated with a proteolytic enzyme. An average of 30.7% more toxin was found in treated than in untreated milk. This result also suggests binding of AFM1 by milk protein.

Aflatoxin B1↗
PubMed1982

Responses of dairy cows to dietary aflatoxin: feed intake and yield, toxin content, and quality of milk of cows treated with pure and impure aflatoxin.

Ten fistulated Holstein cows in midlactation were given daily doses of 13 mg of aflatoxin B1 for 7 days. Six received pure aflatoxin B1; three received an impure preparation that contained aflatoxin B1 plus other aflatoxins and metabolites produced by Aspergillus parasiticus in culture. Toxin was administered to each animal twice daily, one-half of the total dose each time, via the rumen orifice. Morning and evening milks were collected and analyzed for aflatoxin M1. Milk production and feed intake were monitored for 5 days before, every day during, and for 8 days after treatment with aflatoxin B1. Milk contained from 1.05 ppb to 10.58 ppb of aflatoxin M1. None was in milk 4 days after administration of toxin had stopped. Somatic cell counts and standard plate counts from milks of two cows were not affected appreciably by administration of toxin. Fluctuations in feed intake and milk production occurred in all animals during the treatment period with a significant decrease in milk production of those cows receiving 13 mg of impure aflatoxin B1 per day. Differences in results when cows received equal amounts of aflatoxin B1 may be attributable to the type of toxin administered (pure versus impure).

Aflatoxin B1↗
PubMed1981

Biogenesis of the C20 polyketide, aflatoxin. A review.

Aflatoxin B2 is a secondary metabolite produced by the ubiquitous molds Aspergillus flavus and Aspergillus parasiticus. The toxin was first characterized in 1963 as the etiological agent responsible for the infamous "Turkey X' disease. Since that time, much information on its chemistry, toxicity and biological activity has accumulated. A significant amount of work has been done to elucidate its biosynthesis. Evidence indicates the polyketide route as its point of origin. The steps involved in the polyketide pathway, the six identified intermediated compounds, and the experimental techniques and analytical instrumentation used to procure information on aflatoxin biogenesis are included in this review.

Acetates↗
PubMed1981

Heat-stability of peroxidase in mycelia of some toxigenic and nontoxigenic aspergilli and penicillia.

Seven-day-old mycelia from 19 cultures of Aspergillus and 12 cultures of Penicillium were heated to 50, 60, 65, 70, 75, 80, 85, 90 or 95 C for no more than 1 min, and tested for residual peroxidase. The peroxidase from all aspergilli survived heating at 50 through 80 C. Peroxidase from toxigenic strains of Aspergillus flavus, Aspergillus parasiticus and Aspergillus ochraceus survived heating at 85 C and often at 90 C, whereas peroxidase from non-toxigenic strains of A. flavus was inactivated at 90 C and markedly reduced in activity at 85 C. Peroxidase from all penicillia survived heating at all temperatures through 80 C, although the activity of several cultures was reduced at 80 C. Peroxidase activity in mycelia of two strains of Penicillium cyclopium and one of Penicillium puberulum failed to survive heating at 85 C. One strain each of Penicillium roqueforti and Penicillium viridicatum exhibited some peroxidase activity after heating at 90 C, whereas the peroxidase of all other penicillia was inactivated at this temperature.

Aflatoxins↗
PubMed1980

Growth and biosynthesis of aflatoxin by Aspergillus parasiticus in cultures containing nisin.

Nisin, 200 or 5000 Reading units/ml, was added to Aspergillus parasiticus cultures. The cultures were incubated at 28 degrees C for 3, 7 or 10 days and analyzed for mycelial dry weight, pH and accumulation of aflatoxin B1 and G1. During the first 3 days of incubation, dry weight, pH decrease and aflatoxin accumulation were suppressed by nisin, when compared with similar values for the nisin-free control. After longer incubation, differences in dry weight nd pH values decreased, whereas accumulation of aflatoxin in the nisin-containing cultures surpassed that of the control.

Aflatoxin B1↗
PubMed1980

Cook/chill foodservice system with a microwave oven: aerobic plate counts from beef loaf, potatoes and frozen green beans.

The purpose was to evaluate microbiological quality and end temperature (ET) of portioned food after heating in a microwave oven as used in a hospital cook/chill foodservice system. Beef loaf (15 kg), potatoes (6 kg), and green beans (5 kg) were prepared in a laboratory. After initial cooking to 60 degrees C, and storage (7 degrees C for 24 h), beef loaf (100 g) was microwave heated: 20, 50, 80 or 110 s. Potatoes were reconstituted, stored (7 degrees C for 24 h), portioned (100 g/portion), and microwave-heated: 25, 45, 65 or 84 s. Beans were thawed (7 degrees C for 24 h), portioned (100 g/portion), and microwave-heated: 20, 50, 80 or 110 s. Aerobic plate counts (APC) for foods were obtained throughout product flow. Wide ranges of Et and of APC in foods indicates that research is needed, for greater control of microwave-heating through advanced microwave engineering and food technology, to produce food with constant microbiological quality.

Animals↗
PubMed1979

Stability of patulin at ph 6.0-8.0 and 25 degrees c.

Patulin was tested for stability at pH values of 6.0, 6.5, 7.0, 7.5, and 8.0, using Sörensen's phosphate buffer at 25 degrees C. Patulin was determined by high-performance liquid chromatography. When the percentage of patulin remaining was plotted versus reaction time, apparent first-order reaction plots were obtained. Reaction rate constants for disappearance of patulin ranged from 1.1 x 10(-2) h at pH 8.0-5.3 x 10(-4) h at pH 6.0. Values for half-life were calculated and ranged from 64 h at pH 8.0 to 1310 h at pH 6.0.

Hydrogen-Ion Concentration↗
PubMed1978

Aflatoxin is degraded by heated and unheated mycelia, filtrates of homogenized mycelia and filtrates of broth cultures of Aspergillus parasiticus.

Steaming one-half of a lot of 9-day-old mycelia of Aspergillus parasiticus NRRL 2999 for 6 min resulted in little or no subsequent degradation of aflatoxin B1 or G1 by these mycelia. The other half of these mycelia was not heat-treated and degraded aflatoxins B1 and G1. Filtrates of the growth substrate which remained after the mycelium was removed from 8- to 15-day old cultures of A. parasiticus NRRL 2999 did not degrade substantial amounts of aflatoxin B1 or G1, whereas mycelia originally produced on these filtrates degraded substantial amounts of both aflatoxins. The supernatant fluid from homogenates of 9-day-old mycelia of A. parasiticus NRRL 2999 degraded aflatoxins B1 and G1 when 0.1 M or 1.0 M phosphate buffer, pH 6.5, was used to suspend the homogenate. These data support the hypothesis that the aflatoxin degrading factor(s) present in the mycelium of A. parasiticus is/are enzyme(s) or at least influenced by enzyme(s).

Aflatoxins↗