Showing papers on "Agar plate published in 1974"

Isolation, Culture Characteristics, and Identification of Anaerobic Bacteria from the Chicken Cecum

Abstract: Studies on the anaerobic cecal microflora of the 5-week-old chicken were made to determine a suitable roll-tube medium for enumeration and isolation of the bacterial population, to determine effects of medium components on recovery of total anaerobes, and to identify the predominant bacterial groups The total number of microorganisms in cecal contents determined by direct microscope cell counts varied (among six samples) from 383 × 1010 to 764 × 1010 per g Comparison of different nonselective media indicated that 60% of the direct microscope count could be recovered with a rumen fluid medium (M98-5) and 45% with medium 10 Deletion of rumen fluid from M98-5 reduced the total anaerobic count by half Colony counts were lower if chicken cecal extract was substituted for rumen fluid in M98-5 Supplementing medium 10 with liver, chicken fecal, or cecal extracts improved recovery of anaerobes slightly Prereduced blood agar media were inferior to M98-5 At least 11 groups of bacteria were isolated from high dilutions (10-9) of cecal material Data on morphology and physiological and fermentation characteristics of 90% of the 298 isolated strains indicated that these bacteria represented species of anaerobic gram-negative cocci, facultatively anaerobic cocci and streptococci, Peptostreptococcus, Propionibacterium, Eubacterium, Bacteroides, and Clostridium The growth of many of these strains was enhanced by rumen fluid, yeast extract, and cecal extract additions to basal media These studies indicate that some of the more numerous anaerobic bacteria present in chicken cecal digesta can be isolated and cultured when media and methods that have been developed for ruminal bacteria are employed

Aflatoxin-producing strains of Aspergillus flavus detected by fluorescence of agar medium under ultraviolet light.

Abstract: The fluorescence method of detecting aflatoxin-producing strains of Aspergillus flavus and related species utilizes the ultraviolet-induced fluorescence of aflatoxin produced in a modified Czapek's solution agar containing corn steep liquor, HgCl(2), and (NH(4))H(2)PO(4) instead of NaNO(3). The presence of aflatoxin is confirmed by thin-layer chromatography of CHCl(3) extracts of the fluorescing agar.

Haploid plants from anthers of tobacco - Enhancement with charcoal.

Abstract: Haploid plants of Nicotiana tabacum L. were produced in greater numbers from anthers on agar medium containing activated charcoal than on the same medium without charcoal.

An agar medium for the differential enumeration of yogurt starter bacteria1,2

Abstract: Generally, Streptococcus thermophilus ferments sucrose, whereas Lactobacillus bulgaricus fails to utilize this disaccharide. When both sucrose and lactose were added to a basal medium, S. thermophilus fermented both carbon sources, produced sufficient acid to change the color of an acid-base indicator (bromcresol purple), and hence formed yellow colonies. On the same medium, most L. bulgaricus strains grew more slowly, produced less acid, and yielded white colonies. Acid diffusion around the S. thermophilus colonies was localized by incorporation of CaCO3 into the medium. To test the efficacy of this medium when known strains of starters are used, the effect of freezing with liquid nitrogen on mixed cultures of S. thermophilus and L. bulgaricus was studied.

Enumeration of food-borne Clostridium perfringens in egg yolk-free tryptose-sulfite-cycloserine agar.

Abstract: The SFP (Shahidi-Ferguson perfringens), TSC (tryptose-sulfite-cycloserine), EY (egg yolk)-free TSC, and OPSP (oleandomycin-polymyxin-sulfadiazine perfringens) agars have been tested for their suitability to enumerate Clostridium perfringens in naturally contaminated foods. Complete recoveries of C. perfringens were obtained in each of the four media, but only the TSC and EY-free TSC agars were sufficiently selective to ensure subsequent confirmatory tests without interference from facultative anaerobes. Because of some disadvantages associated with the use of egg yolk, EY-free TSC agar is recommended for enumeration of C. perfringens in foods. Several conditions for convenient shipment of foods and C. perfringens isolates with minimum loss of viability have been tested. The highest viable counts were preserved when foods were mixed 1:1 (wt/vol) with 20% glycerol and kept in a container with dry ice. Isolated C. perfringens strains remained viable for at least 2 weeks at ambient temperatures on blood agar slopes with a 2% agar overlay in screw-cap culture tubes.

Paper Disk-Agar Diffusion Assay of Penicillin in the Presence of Streptomycin

Abstract: Microbiological assay of individual antibiotics in mixtures of antibiotics depends on the use of selective inactivation and/or of test bacteria with differential susceptibility. Controlled experiments revealed that streptomycin in concentrations of 20 and 40 μg/ml did not influence a disk diffusion assay of penicillin with Sarcina lutea (ATCC 9341) as the test organism. In the case of penicillin concentrations less than or equal to 1 IU/ml, addition of 80 μg of streptomycin per ml influenced the penicillin assay significantly. Clinical use of streptomycin resulting in levels above 40 μg/ml usually did not occur; therefore penicillin could be assayed as though streptomycin were not present. We observed additionally that S. lutea was unable to grow on agar plates prepared with semicarbazide hydrochloride.

Insect cells: colony formation and cloning in agar medium.

Abstract: An agar medium has been developed which permits formation of colonies from cells of the insect cell lineTrichoplusia ni, with a plating efficiency of 1%. This technique has been successfully applied in the cloning of theT. ni line and is applicable to other insect lines displaying this property. Morphology, growth curves, and population doubling times of several clones are presented.

Bacterial oxidation of manganous ions as affected by organic substrate concentration and composition

Abstract: The ability of a soil Arthrobacter sp. to oxidize manganous ions in agar media containing various proportions and concentrations of sucrose and yeast extract as substrates was examined. Oxidation occurred readily on media ranging from those containing no added substrate to those containing as much as 2 per cent substrate. A variety of patterns of manganese oxide deposition was observed in colonies on various media. On media enriched with yeast extract the oxide was confined to the colonies and consisted of numerous small specks. Enrichment of media with sucrose resulted in the oxide being deposited as large discrete specks both within the colonies and in the agar below and around them. Oxidation did not occur on media which became and remained more acid than pH 6.0 or on those that rapidly became alkaline (pH 8.0). Within these limits increasing substrate concentration improved both growth and oxidation. Both the direction and rate of pH change, and hence the onset of oxidation, were affected by the proportion and concentration of sucrose and yeast extract. Non-oxidizing colonies, on media that had become alkaline, rapidly became oxidizing when exposed to CO2-enriched air. The location of oxidation on agar plates and the time required for the first visible evidence of oxidation on various media are explained on the basis of pH changes during growth. These results are discussed in relation to the selection of media for the isolation and enumeration of manganese-oxidizing micro-organisms, to manganese oxidation by fungi and to the availability of manganese in soils.

Method and apparatus for plating and counting aerobic bacteria

Abstract: A method for determining the concentration of an unknown bacterial solution using only a single bacterial growth plate for the determination. The method comprises depositing a varying amount of bacterial solution on the surface of a solidified agar plate by continuously varying the amount of solution deposited in the shape of a spiral on the agar which is in a rotating Petri dish. Thus, a higher concentration of bacteria per unit length occurs at the center of the spiral and a decreasing concentration per unit length at the edge of the plate. The plate is then incubated and the colonies in a predetermined area of the plate are counted in order to determine the concentration of the unknown solution. The bacterial colonies in a predetermined area may be counted by interrupting a light or laser beam incident to a photodiode, the light being interrupted by the presence of a bacterial colony. The concentration of the unknown solution may then be determined by relating the number of colonies counted to the area on which they were deposited.

Rapid Screening for the Isolation of Mutants of Aspergillus nidulans with Increased Penicillin Yields

Abstract: Summary. After UV treatment conidia of a strain of Aspergillus nidulans were plated on an agar medium. The survivors gave rise to individual colonies which were inoculated separately on agar discs and incubated. The discs were then transferred to biological assay plates seeded with spores of a strain of Bacillus subtilis sensitive to penicillin. Using this primary screening method, mutants have been isolated which, when tested later in shake flask cultures, gave larger penicillin yields than the parent strains.

Acetamide agar for differentiation of nonfermentative bacteria.

Abstract: An acetamide agar medium is described for use in the differentiation of nonfermentative gram-negative bacteria. With few exceptions, indicator reactions were rapid, intense, and clear-cut.

Method for determination of the presence of antibiotics

Abstract: A method for the rapid determination of the presence or absence of residues of antibiotic such as penicillin, in liquids, for example milk, and meat comprising introducing spores of a microorganism which possesses a high sensitivity for the antibiotic to be determined into an agar medium so that the spores are prevented from starting to germ due to lack of nutrients, but stay alive, and being sufficiently heavily inoculated that after addition of nutrients and incubation at or near optimal temperature in a short time sufficient growth has proceeded so that growth is either observable visually or its indicated by an indicator added to the agar medium, the said spore culture being allowed to solidify in upright test vessels having a cross-sectional dimension sufficiently small to require as little of the agar medium as possible but sufficiently large to enable a correct determination of inhibition of growth of the microorganism to be made, and having a height so that the vessel can contain a sufficient amount of medium and a sufficient amount of sample of liquid to be tested, placing on the agar surface nutrients required for growth, followed, if desired, after a pre-incubation period, by addition of a predetermined amount of sample liquid to be tested to the test vessel, and incubating the contents of the test vessel at or near optimal temperature for a predetermined time so that the extent of growth or inhibition of growth of the microorganism read in a vertical sense, indicates absence or presence of the antibiotic.

A Method for the Detection of Starch Hydrolysis by Bacteria

Abstract: Summary. A starch agar medium for the detection of starch hydrolysis is described. The development of a cloudy zone round the colony indicates starch hydrolysis without the use of iodine or 95% (v/v) ethanol.

Thymidine-dependent Escherichia coli infection and some associated laboratory problems.

Abstract: The rapid emergence of a thymidine-dependent strain of Escherichia coli in a patient treated with co-trimoxazole is described. The organism was recovered from blood cultures during a septicaemia which developed after only a few days of co-trimoxazole treatment. The cultural characteristics of three thymidine-dependent strains were studied and a remarkable variation was found in their ability to grow on different batches of blood agar, depending upon the age of the plates and the type of agar base used.

Total Viable Count of Microorganisms in the Infected Dental Pulp

Abstract: A technique for estimating the total viable count of microorganisms in the infected dental pulp is described. The count obtainable using blood agar, tomato juice agar, or Sabouraud's agar solid media is about 106 per tooth. Anaerobes are more numerous than aerobes counted on the blood agar plates. It may be possible to apply this technique for evaluating the efficacy of root canal dressings.

Sensitization of ultraviolet-irradiated Escherichia coli K-12 by different agars: inhibition of A rec and exr gene-dependent branch of the uvr gene-dependent excision-repair process.

Abstract: —E. coli K-12 wild-type cells plated immediately after UV irradiation had a much lower survival on minimal medium solidified with agar-agar No. 3 (Oxoid), purified agar (Difco) or ionagar (Colab) than on plates solidified with laboratory-washed Noble agar (Difco). An intermediate survival was obtained on plates solidified with unwashed Noble agar (Difco). When irradiated cells were incubated in liquid minimal medium for various times before subsequent plating on agar-agar No. 3, their survival increased rapidly and became identical to the survival of cells plated on washed Noble agar. The same phenomenon was found with polA 1 cells, but no differences in survival on the different agars were observed with uvrB, exrA, recA or recB cells. These- data suggest that a repair process dependent on the uvrB, recA, recB and exrA (but not the polA) gene products is inhibited when UV irradiated E. coli K-12 cells are plated on minimal medium solidified with agar-agar No. 3, purified agar or ionagar. This implies that the uvr gene-dependent excision-repair process consists of at least two branches, one controlled by the polA gene and a second controlled by the recA, recB and exrA genes and inhibitable by a substance present in certain agars. For maximum sensitivity, experiments designed to study chemical inhibitors of repair should use agar plates that do not themselves inhibit repair.

Comparison of selective media for the enumeration of sublethally heated food-poisoning strains of Staphylococcus aureus.

Abstract: Staphylococcus aureus strains (19 food-poisoning strains) were heated at 52C for 15 min in 100 mM potassium phosphate buffer. The sublethally heated organisms were enumerated on seven selective med...

Comparison of Media for the Isolation of Haemophilus species from Cases of Seasonal Conjunctivitis Associated with Severe Endemic Trachoma

Abstract: Media for isolation of Haemophilus sp from the conjuctiva were compared in an oasis in southern Tunisia where severe trachoma and seasonal epidemic purulent conjunctivitis are common Of 89 children tested, IsoVitaleX-supplemented chocolate agar yielded Haemophilus in 87%, plain chocolate agar in 75%, sheep blood agar with a stab of Staphylococcus epidermidis in 74%, and Fildes medium in 58% Since other microbial pathogens are easily identified in the modified blood agar, it was the most useful single medium

Tryptic Soy Bile-Kanamycin Test for the Identification of Bacteroides fragilis

Abstract: A simple and practical test for the identification of Bacteroides fragilis is described. It utilizes two well-known properties of this species, i.e., stimulation of growth by bile and resistance to kanamycin. The test media are a tryptic-soy bile agar plate and a supplemented blood agar plate on which a kanamycin 1,000-mug/ml disk is placed. Incubation is for 24 h at 37 C in GasPak. The results of screening 190 strains, mostly clinical isolates, indicate that B. fragilis can be easily and reliably distinguished from other Bacteroides and from Fusobacterium species by its growth on tryptic-soy bile agar and resistance to kanamycin.

Seasonal Occurrence of Several Groups of Heterotrophic Bacteria in Two Reservoirs

Abstract: 75% of the isolated strains were Gram negative, asporogenous bacteria. Almost a half of them fermented glucose, which was probably caused by a selectivity of the agar medium for the particular types. The groups tentatively classified as Enterobacteriaceae and Aeromonas, prevailed during summer, whereas pseudomonads and Acinetobacter were more common in winter.

A selective plating agar for direct enumeration of salmonella in artificially contaminated dairy products1

Abstract: A selective plating medium was developed that allows direct enumeration of salmonellae in dairy products such as nonfat dry milk, and Cheddar and cottage cheese. The agar medium developed was a modification of the Lysine-Iron-Cystine broth of Hargrove et al., 1971. Strains of species of the genera Escherichia, Enterobacter, Citrobacter, Proteus, Shigella, Pseudomonas, and Bacillus were easily differentiated from salmonellae by colony color and color of surrounding area or absence of growth. The antibiotic, novobiocin, used as a selective agent, inhibited growth of some Proteus, Shigella, and Escherichia; however the antibiotic was most effective against Bacillus, without having any observable effect on salmonellae. The medium was sufficiently sensitive and selective to permit detection of as few as 1–2 salmonellae per gram of product in the presence of naturally occurring bacteria and should be of considerable value in following the Salmonella content of artificially contaminated foods during processing a...

Improved rapid plate method for the isolation of bacteriophages from lysogenic bacteria.

Abstract: A modification of a recently reported rapid plate method for the isolation of bacteriophages from lysogenic bacteria is described. The velveteen replica plate technique was used for inoculation of mitomycin C-induced colonies onto agar plates, and tetrazolium chloride was used to enhance detection of phage activity on replicated indicator plates.

Evaluation of media for selective isolation of yeasts from oral, rectal, and burn wound specimens.

Abstract: Six media were evaluated to determine their ability to isolate yeasts and inhibit bacteria The media included the following: Snyder, Snyder tellurite, Sabouraud tellurite, Littman-gentamicin, molybdate, and Mycosel (BBL) Doses of mixed intestinal gram-negative bacilli and enterococci were most effectively inhibited by Snyder tellurite agar Klebsiella pneumoniae was the most common bacterial contaminant of the other media All six media were comparable in isolating yeasts while preventing the growth of the oral bacterial flora The selection of a basal fungal growth medium for tellurite incorporation to inhibit bacteria but permit growth of yeasts was affected by pH The bacteriostatic effect of tellurite was decreased with increasing pH of media while fungistatic action was increased The arbitrary selection of Snyder and Littman agars to isolate yeast from burn wound cultures demonstrated the need to include a selective medium for these specimens Blood, phenylethyl alcohol blood agar, and Columbia CN blood agar were all inadequate for isolating yeasts from burns Growth of a variety of filamentous saprophytic and pathogenic dimorphic fungi grew adequately on four of five selective media tested

Evaluation of three media for selective isolation of gram-positive bacteria from burn wounds.

Abstract: Three media, phenylethyl alcohol blood agar, esculin-mannitol agar, and Columbia CN blood agar, were studied for the selective isolation of gram-positive bacteria from swab cultures of burn wounds.

Evaluation of Media, Time and Temperature of Incubation, and Method of Enumeration of Several Strains of Clostridium perfringens Spores

Abstract: Two basal media, containing the ingredients found in common in both SPS (BBL) and TSN (BBL) media and in the previously described media of Schaedler et al. (1965) and Starr et al (1971), but minus antibiotics, were selected as the most suitable for the enumeration of Clostridium perfringens spores in a model system. These media were also used to study the influence of the presence of glucose, xylose, or ribose in various concentrations (0, 0.01, 0.1, and 1.0%) on colony morphology and spore recovery. As the sugar concentration in the basal agar medium increased, the colonies of all the test organisms also increased in size, and more of the black colonies became white in color. At the 1.0% sugar level, glucose permitted only white colony development, whereas the pentoses were completely inhibitory. Both pour plates and most-probable-number tubes were inoculated with the spores of several strains of C. perfringens and incubated at 20, 30, 37, and 45 C for 24, 48, and 72 h. Statistical analyses of the enumeration data indicated, at the 99% confidence level, that a Trypticase(BBL)-yeast extract-glucose-sulfite-iron agar gave maximal population estimates at 37 C in 72 h.

Multi-differential agar culture medium

Abstract: A multi-differential agar culture medium which has the capability to differentiate between a large variety of closely related bacterial species, comprising tomato juice, peptonized milk, yeats extract, glucose, calcium pantothenate, a pH lowering agent, a non-diffusible buffering agent, metals and minerals, a wetting agent and stimulator of growth of lactic acid bacteria, an acid-base color indicator, a yeast suppressing agent, and agar.