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Biomedical subjects

E S Idziak

Publications and source records attributed to E S Idziak.

16 recordsLinked to original sources
PubMed1996

Comparative assessment of bacterial inoculation and propionic acid treatment of aerobic stability and microbial populations of ensiled high-moisture ear corn.

High-moisture ear corn (HMEC) was untreated, treated with propionic acid (PA), or inoculated with a mixture of Lactobacillus plantarum and Enterococcus faecium and allowed to ensile in laboratory silos for 0, 7, 21, 42, 138, or 202 d. The silages were evaluated for fermentation quality, microbial populations, and aerobic stability. In all treatments, silage pH declined rapidly within 7 d, but the rate of decline seemed greatest with the inoculum. The lactic acid content of inoculated HMEC was higher (P < .05) than that of control of PA-treated HMEC. Regardless of treatment, the population of lactic acid bacteria (LAB) increased (P < .1) up to 7 to 21 d of fermentation then declined; LAB counts decreased (P < .05) up to 42 d in control and PA-treated silage but continued to decline until 138 d for inoculated silage. Yeast and mold counts tended to decrease up to 42 d of ensiling then decreased (P < .05) as fermentation progressed. Between 138 and 202 d of ensiling, the control silage showed a marked increase (P < .10) in pH and yeast and mold populations, providing evidence of secondary fermentation; PA treatment and bacterial inoculation prevented secondary fermentation. Inoculation tended to reduce estimates of sample temperature for silage stored for 138 d and exposed to air, but not for the corresponding silage stored for 202 d. Treatment with PA prevented the loss (P > .05) of acetic acid and the rise (P > .05) in pH during air exposure of the 138-d silage; both control and PA-treated silage showed an increase (P < .05) in yeast and mold populations, but the increments were 38% and 23%, respectively. Compared with PA, the relative efficacy of inoculation in improving aerobic spoilage of HMEC depended on the period of silo storage and the criterion used to assess aerobic stability.

Acetates↗
PubMed1992

A model study of factors involved in adhesion of Pseudomonas fluorescens to meat.

A study was undertaken to investigate the factors involved in the adhesion of Pseudomonas fluorescens to model meat surfaces (tendon slices). Adhesion was fast (less than 2.5 min) and was not suppressed by killing the cells with UV, gamma rays, or heat, indicating that physiological activity was not required. In various salt solutions (NaCl, KCl, CaCl2, MgCl2), adhesion increased with increasing ionic strength up to 10 to 100 mM, suggesting that, at low ionic strengths, electrostatic interactions were involved in the adhesion process. At higher ionic strengths (greater than 10 to 100 mM) or in the presence of Al3+ ions, adhesion was sharply reduced. Selectively blocking of carboxyl or amino groups at the cell surface by chemical means did not affect adhesion. These groups are therefore not directly involved in an adhesive bond with tendon. Given a sufficient cell concentration (10(10) CFU.ml-1) in the adhesion medium, the surface of tendon was almost entirely covered with adherent bacteria. This suggests that if the adhesion is specific, the attachment sites on the tendon surface must be located within collagen or proteoglycan molecules.

Animals↗
PubMed1992

Plasmids in Listeria monocytogenes and other Listeria species.

One hundred and twenty-two food, clinical, and veterinary strains of Listeria monocytogenes were examined for the presence of plasmids. Twenty-five (20%) contained plasmids, which varied from 1.3 to 66 MDa in size. Of 10 strains of other Listeria species (L. innocua, L. ivanovii, L. welshimeri, L. seeligeri, L. grayi, and L. murrayi) examined, seven (70%) contained plasmids, varying from 38 to 53 MDa. No strains with multiple plasmids were found. Plasmids of identical size were isolated from related strains in some, although not all, cases. The presence of a plasmid in a strain was not related to phenotypic characters of known extrachromosomal inheritance.

Animals↗
PubMed1991

Detection of Listeria monocytogenes by direct colony hybridization on hydrophobic grid-membrane filters by using a chromogen-labeled DNA probe.

A DNA probe specific for Listeria monocytogenes was isolated from a beta-hemolytic recombinant clone of an L. monocytogenes gene bank. It was labeled with horseradish peroxidase and used in a direct colony hybridization method on hydrophobic grid-membrane filters for the detection of the organism. Following color development of the chromogen, a commercial counter (HGMF Interpreter) was able to detect and count the organisms electronically. The method gave a positive reaction with 70 L. monocytogenes strains, while showing a negative reaction with 10 strains of other Listeria spp. and with 20 organisms of other genera.

Chromogenic Compounds↗
PubMed1991

Role of flagella in adhesion of Pseudomonas fluorescens to tendon slices.

Tendon slices were used as model surfaces to investigate the role of flagella in the adhesion of Pseudomonas fluorescens to meat. The slices were introduced into a specially designed flow chamber, which was then filled with a suspension of the organism, and the tendon surface was observed at a x640 magnification. The same events that occur during the colonization of glass surfaces (apical adhesion of cells with rotation around the contact point, longitudinal adhesion, detachment of apically and longitudinally adherent cells) were also observed on tendon. Mechanical removal of the flagella resulted in no change in the contact angles with 0.1 M saline or alpha-bromonaphthalene, in the electrophoretic mobility, or in the adhesion of the organism to hydrophobic and ion-exchange resins. In addition, cells from which flagella had been mechanically removed still adhered extensively to tendon. Nevertheless, under comparable conditions (bacterial concentration, contact time), flagellated cells adhered to tendon in larger numbers than did deflagellated cells. This was entirely due to the ability of the motile flagellated cells to reach tendon in greater numbers than deflagellated cells.

Animals↗
PubMed1989

New method to study bacterial adhesion to meat.

A new method was developed for the study of bacterial adhesion to meat surfaces. Thin slices of meat (40 microns thick) were inserted into a specially designed observation chamber. The meat slices were then exposed to a bacterial suspension (ca. 10(6) CFU.ml-1) to initiate adhesion (20 min of contact time) and subsequently rinsed to eliminate nonadherent bacteria. Because of the special chamber design, the disruptive force exerted on the bacteria during rinsing (shear stress) was uniform over the whole surface of the meat slices, was constant, and could be varied from 0 to 0.08 N.m-2. After being rinsed, the meat slices were stained with basic fuschin and observed under light microscopy to determine the number and distribution of adherent bacteria. This new method was used to study the adhesion of Acinetobacter strain LD2, a Lactobacillus sp., and Pseudomonas fluorescens to slices of beef fat and tendon. At 25 degrees C, most (greater than or equal to 99.9%) of the cells of the Lactobacillus sp. deposited on the meat were washed off the surface during rinsing (0.05 N.m-2), whereas a large number (ca. 10(5) CFU.cm-2) of Acinetobacter strain LD2 and P. fluorescens cells remained adherent. The extent of adhesion was similar on fat and tendon, and adherent bacteria were distributed evenly over the whole surface of the slices. This preliminary study indicates that the combined use of thin slices of meat and of the observation chamber provides us with the means to more accurately study bacterial adhesion to meat surfaces.

Acinetobacter↗
PubMed1985

Interaction between Streptococcus lactis and Aspergillus flavus on production of aflatoxin.

The inoculation of Aspergillus flavus spores into a culture of Streptococcus lactis in Lablemco tryptone broth medium resulted in little or no aflatoxin accumulation even though the growth of the fungus was not hindered. The drop in pH and reduced nutrient levels in the medium as a result of the S. lactis growth were not the cause of the observed inhibition. The inhibition was not eliminated by the addition of carbohydrate equal to the amount used by the bacterium before the inoculation with the fungus. Aflatoxin levels were also markedly reduced when S. lactis was inoculated into a growing A. flavus culture. In addition to inhibiting the synthesis of aflatoxin, S. lactis also degraded preformed toxin. A. flavus, on the other hand, not only reduced the growth of S. lactis but also affected the morphology of the bacterial cell; the cells became elongated and formed long chains. S. lactis produced and excreted the inhibitor into the medium late in its growth phase. The inhibitor was a heat-stable low-molecular-weight compound. Chloroform extracts of A. flavus grown in the presence of S. lactis were toxic to Bacillus megaterium but did not exhibit mutagenic or carcinogenic activity in the Salmonella/mammalian microsome mutagenicity test.

Aflatoxins↗
PubMed1982

Detection of glucose oxidation products in chilled fresh beef undergoing spoilage.

The fate of nutrients during storage of longissimus dorsi muscle at 4 degrees C was examined. Glucose concentrations in meat were shown to decrease concomitantly with an approximately fourfold increase in the activity of glucose dehydrogenase. Gluconate concentrations in meat were determined by an enzyme assay and shown to increase from 2.1 to 40.6 microgram/g upon storage of the meat from day 0 to day 6. At day 12, gluconate concentrations had decreased to 5.8 microgram/g. Dark firm dry meat, which contains little or no glucose, did not exhibit the same rise and fall in gluconate concentration. Thin-layer chromatographic analysis confirmed the presence of 2-ketogluconate in 6- and 12-day-old longissimus dorsi muscle that had been stored at 4 degrees C. Gluconate concentrations in irradiated sterile meat inoculated with Pseudomonas fluorescens increased from 4.2 to 77.8 microgram/g during the first 6 days of storage at 4 degrees C. Therefore, glucose in meat stored at 4 degrees C appeared to be converted to gluconate, 2-ketogluconate, or both extracellularly by one of the main meat spoilage organisms, most likely the pseudomonads.

Animals↗
PubMed1970

Radiation treatment of foods. II. Public health significance of irradiation-recycled Salmonella.

Salmonellae resistant to gamma irradiation were developed by repeated irradiation and subculturing in a nutrient broth-yeast extract medium. Few differences were noted in the biochemical characteristics of parent and resistant cultures; however, microculture studies revealed variations in morphology and in cell division patterns. A considerable decrease in pathogenicity for day-old chicks was apparent with resistant cultures, but their phenol-water extracts were as toxic as parent material for 10-day chick embryos. Five serial chick passages did not reverse the reduced pathogenicity or aberrant morphology of a resistant Salmonella typhimurium culture. Results of phage typing of both parent and serially irradiated S. typhimurium were inconclusive, whereas the O-1 genus-specific phage lysed all parent serotypes tested but only one of the serially irradiated cultures. Agglutination of parent S. typhimurium cells with their homologous rabbit antiserum was unaffected by prior absorption with resistant strains. The results indicate that radiation recycling altered Salmonella into strains of lesser public health significance.

Agglutination Tests↗
PubMed1968

Radiation treatment of foods. I. Radurization of fresh eviscerated poultry.

Radurization processing of fresh eviscerated poultry has been microbiologically studied. The recommended dose of 0.5 Mrads extended the shelf life at 5 C by approximately 14 days. This treatment also effected a 10 and 11 log reduction in the number of viable Salmonella species and Staphylococcus aureus strains, respectively. Recycling these organisms at sublethal doses of irradiation resulted in strains possessing increased irradiation resistance. Shifts in the microbial ecology after irradiation and storage resulted, in some instances, in the isolation of organisms tentatively identified as Moraxella sp. and Herellea vaginicola.

Food Irradiation↗