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Showing papers on "Agar plate published in 1987"


Journal ArticleDOI
TL;DR: The universal method to detect and determine siderophores was developed by using their high affinity for iron(III) and was successfully used to screen mutants in the iron uptake system of two Rhizobium meliloti strains, DM5 and 1021.

5,499 citations


Journal ArticleDOI
TL;DR: The authors were able to isolate Bacillus thuringiensis from environmental samples with a background of 10 bacteria per g of soil with a selection process differed significantly from classical selection methods which permit only the desired organism to grow.
Abstract: We were able to isolate Bacillus thuringiensis from environmental samples with a background of 109 bacteria per g of soil. Our selection process differed significantly from classical selection methods which permit only the desired organism to grow. In our process, germination of B. thuringiensis spores was selectively inhibited by sodium acetate, while most of the undesired sporeformers germinated. Next, all of the nonsporulated microbes were eliminated by heat treatment at 80°C for 3 min. The surviving spores were then plated on a rich agar medium and allowed to grow until they sporulated. Of random colonies picked from agar, 20 to 96% were crystal-forming Bacillus species. B. thuringiensis and B. sphaericus were routinely selected by this method.

431 citations


Journal ArticleDOI
TL;DR: The viable counts were 2–4% of the total microscopical counts in different soils, and assuming that the colony-forming cells did not derive from the numerous "dwarf" cells present in soil, a calculated percent viability of the larger cells was about 10%.
Abstract: Viable counts of heterotropic soil bacteria were 3–5 times higher on low-nutrient agar media compared with a series of conventional agar media. Substantial amounts of monosaccharides and amino acids were present in solid media made from distilled water and agar powder, and a salt-solution agar medium (without organic substrates added) gave practically the same colony counts as the low nutrient soil extract agar medium. MPN values were comparable to or lower than plate counts. A search for slow-growing cells in the negative MPN tubes by fluorescence microscopical examination after 3 months incubation was negative. The viable counts were 2–4% of the total microscopical counts in different soils. Assuming that the colony-forming cells did not derive from the numerous “dwarf” cells present in soil, a calculated percent viability of the larger cells was about 10%. The ecological significance of the plate-counting technique is discussed.

344 citations



Journal ArticleDOI
TL;DR: Nine isolates of Aspergillus flavus and As pergillus parasiticus were screened for aflatoxin production on a coconut extract agar medium and several types of shredded coconut available in the United States were found to be satisfactory.
Abstract: Nine isolates of Aspergillus flavus and Aspergillus parasiticus were screened for aflatoxin production on a coconut extract agar medium. Aflatoxin-producing colonies were detected under long-wave UV light (365 nm) by blue fluorescence on the reverse side after 2 to 5 days of growth. Aflatoxin production was verified by chemical analysis. Several types of shredded coconut available in the United States were tested and found to be satisfactory. No additives were required. Various parameters affecting the test were investigated.

158 citations


Journal ArticleDOI
TL;DR: In this article, the positive aspects of mA agar and dextrin-fuchsin-sulphite agar were combined in a new medium, ampicillin-dextrin agar.
Abstract: Published selective media were evaluated for the isolation of Aeromonas spp. from environmental samples by membrane filtration. Satisfactory recoveries were obtained only with mA agar (Rippey & Cabelli) and dextrin-fuchsin-sulphite agar (Schubert), but neither was sufficiently selective. The positive aspects of these two media were combined in a new medium, ampicillin-dextrin agar. Recovery from pure cultures and environmental samples was optimal at an ampicillin concentration of 10 mg/l and incubation for 24 h at 30 degrees C under aerobic conditions, and specificity was high (i.e. confirmation rate usually greater than 90%, no false negative colonies encountered). The medium can also be used for isolation of Aeromonas spp. from sea water provided that the vibriostatic agent 0/129 is added at 50 mg/l.

143 citations


Journal ArticleDOI
TL;DR: A giant bacterium closely resembling Hyphomicrobium and a budding one similar to Pasteuria were recovered from all samples of a single spring and from some of the commercial samples.
Abstract: A quantitative study of bacterial populations in mineral water was carried out. Samples were stored at 6 and 20 °C, and the colony counts were determined on tryptone agar plates incubated at 22 and...

91 citations


Journal ArticleDOI
TL;DR: The results show that some form of supplementation is necessary for growth of C. pyloridis, a newly discovered organism associated with gastritis and peptic ulcers, and hemin is not an absolute requirement for growth.
Abstract: Experiments were conducted to define the growth requirements of Campylobacter pyloridis, a newly discovered organism associated with gastritis and peptic ulcers. Two clinical isolates were streaked onto various media, and growth was assessed semiquantitatively according to relative colony size and extent of growth through the streak. The growth obtained on fresh chocolate agar, composed of GC agar base (Difco Laboratories, Detroit, Mich.) plus 1% hemin, was used as a reference. The organism grew on both GC agar base and Mueller-Hinton agar without supplementation, but less well than on chocolate agar. No growth occurred on tryptic soy or brucella agar. Supplementation of brucella agar with 1 or 5% horse serum or 0.1 or 1.0% cornstarch supported growth to about the same level as GC agar base alone. Supplementation with hog gastric mucin or methyl cellulose supported weak growth. GC agar base with 1% starch or 0.2% charcoal supported growth as well as chocolate agar. Experiments with brucella broth provided similar results. Cornstarch and methyl cellulose partially replaced the requirement for serum, but methyl cellulose and hog gastric mucin did not. These results show that some form of supplementation is necessary for growth of C. pyloridis. This can be starch, serum, charcoal, or hemin, but hemin is not an absolute requirement for growth.

90 citations


Journal ArticleDOI
TL;DR: A medium was developed for the differential enumeration of homofermentative and heteroferMENTative lactic acid bacteria and a total of 21 Lactobacillus, Pediococcus, Leuconostoc, and Streptococcus species were correctly classified with the medium.
Abstract: A medium was developed for the differential enumeration of homofermentative and heterofermentative lactic acid bacteria. Essential components of the medium included fructose (14 mM), KH2PO4 (18 mM), bromcresol green (as a pH indicator), and other nutrients to support growth. In agar medium, homofermentative colonies were blue to green, while heterofermentative colonies remained white. A total of 21 Lactobacillus, Pediococcus, Leuconostoc, and Streptococcus species were correctly classified with the medium.

87 citations


Journal ArticleDOI
TL;DR: It would seem that a simple correlation between high surface pH and antibacterial activity among these cements does not exist, and further biological characterization of new lining cements is required to direct their appropriate clinical use.
Abstract: The antibacterial activity of innovative, commercial lining cements was investigated. A liner which contains calcium hydroxide and is polymerized by visible light (Prisma VLC Dycal) and a glass-ionomer lining cement (GC lining cement) were compared with two more established lining cements (Advanced Formula II Dycal and Life). Antibacterial activity and hemolysis-like agar change at 24, 48, and 72 hours were measured on blood agar plates inoculated with Streptococcus mutans KPSK 2 (serotype c), Lactobacillus casei ssp rhamnosus ATCC 11981, and chewing-stimulated saliva. Prisma VLC Dycal did not affect bacteria or agar. The glass-ionomer lining cement, with an acidic pH at setting, had the most pronounced effect on all test organisms and on the agar. Even after 48 hours' setting, it inhibited growth of S. mutans. The control lining cement (AFII Dycal) showed antibacterial activity toward both specific micro-organisms as well as some activity against the salivary organisms. The material Life showed only partial inhibition of microbial growth. For all lining cements, the hemolytic-like agar change correlated with antibacterial effects. The surface pH of the freshly-set cements containing calcium hydroxide was alkaline. It would seem that a simple correlation between high surface pH and antibacterial activity among these cements does not exist. Also, further biological characterization of new lining cements is required to direct their appropriate clinical use.

83 citations


Journal ArticleDOI
TL;DR: Very good correlation between the two methods was obtained and this simplified S. mutans detection system is suitable for use by clinical personnel in dental clinics or other non-laboratory settings for identification of subjects potentially at risk for caries.
Abstract: A simple dip-slide test (Cariescreen SM) based on MSB selective agar was devised for detection and quantitation of Streptococcus mutans in oral samples. For this test, a bacitracin tablet is dissolved in a vial containing buffered saline diluent. Paraffin-stimulated saliva is collected in this diluent vial. A dip slide which incorporates a modified MSB agar (minus bacitracin) is immersed briefly in the diluted saliva. After addition of a CO2-generating tablet, the screw-cap dip slide is closed tightly in the vial and incubated for two days at 37 degrees C and one day at room temperature. S. mutans populations in saliva are estimated by comparison with a colony density chart. Growth of reference strains of S. mutans was equivalent on Cariescreen SM dip slides and on MSB agar plates. Reference strains of Streptococcus sanguis, Streptococcus salivarius, Streptococcus mitis, and Streptococcus milleri did not grow on Cariescreen SM dip slides. Aliquots of saliva from 50 schoolchildren and 51 adults were tested by the dip-slide method and by conventional plating methods in MSB agar. Very good correlation (0.93) between the two methods was obtained. This simplified S. mutans detection system is suitable for use by clinical personnel in dental clinics or other non-laboratory settings for identification of subjects potentially at risk for caries.

Journal ArticleDOI
TL;DR: One of the artificial humic acids, which was prepared from glucose and urea, was considered to be superior to the Rp natural humic acid, and produced the same large number of actinomycete colonies on the plate as that of the HV agar with type Rp soil humic Acid.

Journal ArticleDOI
TL;DR: The greatest advantage of VYE agar is that virulent Y. enterocolitica, which forms red colonies, is easily differentiated from most environmental Yersinia organisms and other gram-negative bacteria, which form dark colonies with a dark peripheral zone as a result of esculin hydrolysis.
Abstract: A selective agar medium for isolation of virulent Yersinia enterocolitica (VYE agar) was developed for the rapid and accurate isolation of virulent Y. enterocolitica from environmental samples highly contaminated with environmental Yersinia organisms, as well as for isolation from clinical specimens. VYE agar provided a quantitative recovery of 51 different strains of virulent Y. enterocolitica at 32 degrees C after incubation for 24 h. The cefsulodin, irgasan, josamycin, and oleandomycin content of the medium resulted in a high selectivity, and the mannitol and esculin content provided some differentiation. The greatest advantage of VYE agar is that virulent Y. enterocolitica, which forms red colonies, is easily differentiated from most environmental Yersinia organisms and other gram-negative bacteria, which form dark colonies with a dark peripheral zone as a result of esculin hydrolysis. Use of VYE agar led to a high recovery of Y. enterocolitica biotype 3B serotype O:3 strains from experimentally inoculated meat samples, compared with use of CIN agar. Biotype 2 serotypes O:5,27 and O:9 and biotype 1 esculin-negative serotypes O:4,32, O:8, O:13a,13b, O:18, O:20, and O:21 (American types) were readily differentiated from other environmental organisms able to grow on VYE agar. Epidemiological studies on Y. enterocolitica should be greatly facilitated by the use of this selective agar medium.

Journal ArticleDOI
TL;DR: Results indicate that the UV photography technique can be used as a simple, safe, and rapid method of screening aflatoxin-producing molds.
Abstract: UV absorption by aflatoxins was monitored in GY agar medium by UV photography. In the UV photographs, aflatoxin-producing molds were identified as gray or black colonies, whereas aflatoxin-nonproducing molds appeared as white colonies. By cellophane transplantation experiments and silica gel thin-layer chromatography, the products absorbing UV light substantially were found to be mainly aflatoxins B1 and G1 excreted from the mold mycelium into the agar medium. UV absorption did not occur when the agar medium contained aflatoxin-noninducible carbon sources instead of glucose. Various inhibitors of aflatoxin production, such as dichlorovos and dimethyl sulfoxide, also decreased the intensity of UV absorption. These results indicate that this technique can be used as a simple, safe, and rapid method of screening aflatoxin-producing molds.

Journal ArticleDOI
TL;DR: Biochemical and morphological characteristics of 17 strains of B. cereus, including 10 isolated from confirmed foodborne outbreaks, were studied by routine methods, finding no single feature typified pathogenic strains.

Journal ArticleDOI
TL;DR: Three serological methods are described for additional rapid immunoidentification of colonies directly on agar plates and for screening for cross-reacting microorganisms: direct immunodiffusion on dilution plates, agar mixed-antibody assay, and fluorescent antibody colony staining.
Abstract: Antibodies coated onto a suitable solid phase, e. g. polystyrene beads, rods for inoculating agar plates, or petri dishes, enable selective trapping of homologous bacteria and of immunologically related bacteria by immunoaffinity. After washing away unbound organisms, the bound organisms are desorbed and plated on a suitable medium. Selective immunoisolation has been demonstrated for various phytopathogenic bacteria including Corynebacterium michiganense ssp. michiganense, Erwinia chrysanthemi, E. carotovora ssp. atroseptica, Xanthomonas campestris pv. begoniae and Pseudomonas syringae pv. phaseolicola. Three serological methods are described for additional rapid immunoidentification of colonies directly on agar plates and for screening for cross-reacting microorganisms: (a) direct immunodiffusion on dilution plates, (b) agar mixed-antibody assay, (c) fluorescent antibody colony staining. Schemes are presented for increasing the reliability and sensitivity of sample screening for quality indexing of plant material, and for efficient screening and isolation of possible cross-reacting microorganisms to enable production of more specific antisera.

Journal ArticleDOI
TL;DR: The results indicate that encapsulation is common in bovine staphylococci and while it is lost on subculture, may be retrieved under appropriate conditions.

Journal ArticleDOI
TL;DR: The indirect immunoperoxidase test using small, square filter paper was used for rapid identification of mycoplasmas, and the results agreed with those obtained by growth inhibition test.
Abstract: The indirect immunoperoxidase test using small, square filter paper was used for rapid identification of mycoplasmas. Colonies of type strains of 22 mycoplasma species, 3 acholeplasma species, and three Ureaplasma diversum serogroups were stained by this test with high sensitivity and specificity. All of 49 isolates from bovine materials and cell cultures were easily identified by this test, and the results agreed with those obtained by growth inhibition test. Use of filter paper made it possible to add different kinds of antisera or conjugates to the same agar plate simultaneously and also to save antiserum and conjugate. This test proved to be a simple and useful technique for rapid identification of many mycoplasma species grown on agar medium.

Journal ArticleDOI
TL;DR: The discrepancy in the consistent presence of the organism in retail meat suggests that many of the food isolates are probably not of fecal origin.

Journal ArticleDOI
G.F. Senyk1, S.M. Kozlowski1, P.S. Noar1, W.F. Shipe1, D.K. Bandler1 
TL;DR: Standard plate counts, psychrotrophic bacterial counts, and coliforms were determined by conventional plating techniques and by Petrifilm TM plates, a dry culture medium, for 48 commercially processed milk samples and there was a strong linear relationship between PetrifILm SM and standard methods agar plates and for the psych rotrophic bacterial count method.

Journal Article
TL;DR: An unstable L-form of Staphylococcus aureus was identified in milk samples from 3 quarters of 2 cows after treatment with cloxacillin and was confirmed on transfer to blood agar plates.
Abstract: An unstable L-form of Staphylococcus aureus was identified in milk samples from 3 quarters of 2 cows after treatment with cloxacillin. Milk samples incubated on standard 5% blood agar plates were culture-negative for 7 to 30 days after treatment, but S aureus was reisolated in 80% of 66 samples by additional culturing on enriched L-form media when incubated in 10% CO2 at 37 C. The organism was identified at various phases of reversion of L-form agar and was confirmed on transfer to blood agar plates.

Journal ArticleDOI
TL;DR: Using simple laboratory media, DNase, and superoxol tests, it was possible to identify B catarrhalis and to distingish it from pathogenic and non-pathogenic Neisseria species.
Abstract: To distinguish Branhamella catarrhalis from Neisseria species a study of 140 strains was made on simple laboratory media, with particular reference to deoxyribonuclease (DNase) production, superoxol reaction, and growth characteristics. All 97 clinical isolates of B catarrhalis (58 of which were beta-lactamase positive) and eight strains of B catarrhalis from the National Collection of Type Cultures were DNase positive and superoxol positive. None grew on modified New York City medium, modified Thayer Martin medium, MacConkey agar, crystal violet blood agar, nor under anaerobic conditions. Of the 16 different non-pathogenic Neisseria species tested, all were DNase negative, eight (50%) were superoxol reaction negative, and 13 (81%) grew on crystal violet blood agar. Using simple laboratory media, DNase, and superoxol tests, it was possible to identify B catarrhalis and to distingish it from pathogenic and non-pathogenic Neisseria species.

Journal ArticleDOI
TL;DR: The main role of tampons in toxic shock syndrome may be that of providing a fibrous surface for heavy colonization and sufficient air for TSST-1 production.
Abstract: The influence of 17 commercially available tampons on production of toxic shock syndrome toxin 1 (TSST-1) by Staphylococcus aureus was investigated by using a tampon disk method. Filter membranes overlaying agar medium (with or without blood) in small petri dishes were spread inoculated with a TSST-1-producing strain of S. aureus. Disks cut from unrolled tampons were pressed and laid on the inoculated membranes; incubation was for 19 h at 37 degrees C with 5% CO2 in air. CFU on the membranes and in the disks were enumerated, and the presence of TSST-1 in the disks and in the agar layers was determined. Tampons made of different materials supported characteristic levels of cell growth and toxin production in the tampon. Colonization of the interface surface of the tampon disks was heavy. The number of CFU extracted from the tampon disks ranged from 5 X 10(10) to 82 X 10(10). There was little variation in the CFU recovered from the membranes ([1.9 +/- 0.4] X 10(11)). Sixty to 170 micrograms of TSST-1 was recoverable from the agar, with an additional 10 to 90 micrograms recoverable from tampon disks, depending on the type of tampon disk. The amount of toxin in the agar layer from the various tampon disks was relatively constant and indicated an important contribution of toxin from vaginal S. aureus cells not growing in the tampon. The main role of tampons in toxic shock syndrome may be that of providing a fibrous surface for heavy colonization and sufficient air for TSST-1 production.

Journal ArticleDOI
TL;DR: The growth of colonies of Rhizoctonia cerealis and Penicillium chrysogenum on solid media in plate cultures was studied and the concentration of penicillin in the medium throughout the plate increased with colony development and thereafter, except at the margins of the plate, decreased.
Abstract: The growth of colonies of Rhizoctonia cerealis and Penicillium chrysogenum on solid media in plate cultures was studied. When grown on defined media containing 10-50 mM-glucose, R. cerealis did not cause a significant reduction in the glucose concentration of the medium in advance of colonization, but did cause the formation of a steep glucose concentration gradient in the substrate below the colony; the medium directly below the centre of a 7 cm diameter colony of R. cerealis was exhausted of glucose even when the fungus was grown on medium containing 50 mM-glucose. Penicillin produced by colonies of P. chrysogenum accumulated in the medium in advance of fungal colonization. For a period up to about 18 d after inoculation, the concentration of penicillin in the medium throughout the plate increased with colony development and thereafter, except at the margins of the plate, decreased.

Journal ArticleDOI
TL;DR: The results from the assay confirm the presence in Ureaplasma urealyticum of phospholipase C, which is predominantly localized in the membrane fraction.
Abstract: A screening assay for phospholipase C using a chromogenic substrate incorporated into agar medium is described. The assay directly visualizes phospholipase C activity of mycoplasma lysates and membranes on agar plates, or the activity may be measured by spectrophotometry. The results from the assay confirm the presence in Ureaplasma urealyticum of phospholipase C, which is predominantly localized in the membrane fraction. The procedure has the potential to screen phospholipase C activity in other mycoplasmas and microorganisms in general.

Journal ArticleDOI
TL;DR: The cultivation of Herpetosoma trypanosomes in insect tissue culture media supplemented with foetal calf serum proved the most suitable media for growth of all parasites except T. nabiasi from rabbits which was not successfully established.
Abstract: The cultivation of Herpetosoma trypanosomes in insect tissue culture media supplemented with foetal calf serum is described. Trypanosoma lewisi and T. musculi, which can be grown in blood agar media, were compared with four other species of Herpetosoma trypanosomes, T. microti, T. evotomys, T. grosi and T. nabiasi, in their growth in Schneider's Drosophila medium, Grace's, Mitsuhashi-Maramorosch, RPMI 1640, TCM 199 and nutrient blood agar media. Schneider's Drosophila and Grace's media supplemented with 20% foetal calf serum proved the most suitable media for growth of all parasites except T. nabiasi from rabbits which was not successfully established. Primary cultures were passaged after approximately 3 weeks and were maintained to continuously produce metacyclic trypomastigotes which produced less virulent infections although they maintained their infectivity to their respective hosts. The growth patterns in culture and morphology of the parasites are described.

Journal ArticleDOI
TL;DR: After electrophoresis, active pullulanase bands in acrylamide gels have been detected by overlaying and then incubating the gel on a replica gel containing 2.5%Pullulan-reactive red conjugate and 2.1% agar and the enzyme activity is revealed as a clear band against a red background on the replica gel.

Journal ArticleDOI
TL;DR: Two improved selective culture media were developed for isolation and enumeration of Actinobacillus actinomycetemcomitans (A medium) and Haemophilus aphrophilus (H medium) in oral specimens and suppressed the growth of pure cultures of Capnocytophaga spp.
Abstract: By modifying the previously described media tryptic soy-serum-bacitracin-vancomycin (TSBV) agar and tryptic soy-serum-bacitracin-vancomycin-fluoride (TSBVF) agar, two improved selective culture media were developed for isolation and enumeration of Actinobacillus actinomycetemcomitans (A medium) and Haemophilus aphrophilus (H medium) in oral specimens. Both media were supplemented with fusidic acid and spiramycin, and carbenicillin was also added to A medium. The growth yields of pure cultures of A. actinomycetemcomitans on A medium and of H. aphrophilus on H medium were comparable with those on the reference media. Compared with blood agar, the selective media inhibited these species about 10-fold or less. In addition, A and H media suppressed the growth of pure cultures of Capnocytophaga spp. and Neisseria spp., commonly found as contaminants on TSBV and TSBVF, 10(5) times or more compared with that on blood agar. In samples from diseased periodontal pockets, the recoveries of A. actinomycetemcomitans on A medium and H. aphrophilus on H medium equaled those on TSBV and TSBVF, respectively. In about 50% of the cultures on the reference media, contaminating bacteria were detected at levels higher than 10(4) CFU/ml of sample. The corresponding value for both A and H media was about 2%.

Journal ArticleDOI
TL;DR: The morphology of fruiting bodies of myxobacteria on the agar medium in the laboratory was investigated on the basis of morphological characteristics and production of diffusible light yellow pigment.
Abstract: Myxobacteria were isolated in Japan from soils, decaying plant materials, and tree bark. The isolation methods we have used are the rabbit dung method, placing soil on bacterial smears, the filter paper method, and the agar medium method. Placing soil on bacterial smears was easy to manage. Addition of dealkaline lignin stimulated formation of well- differentiated fruiting bodies on agar medium. This made it possible to investigate the morphology of fruiting bodies of myxobacteria on the agar medium in the laboratory. The myxobacteria isolated and purified were found to be strains of the genera Myxococcus and Archangium. Isolates were identified as Myxococcus stipitatus, Myxococcus fulvus, Myxococcus coralloides, and Archangium gephyra. A new species Myxococcus flavescens is proposed on the basis of morphological characteristics and production of diffusible light yellow pigment. All the tested strains gave positive reactions in catalase and urease. The DNA base composition of the myxobacteria examined ranged from 65 to 67mol% of guanine plus cytosine. The major quinone was menaquinone with 8 isoprenoid units (MK-8). The major cellular fatty acids were iso 15:0, iso 17:0, and 16:1.

Journal ArticleDOI
TL;DR: Yeast isolates seeded in agar plates and overlaid with ‘killer’ fungi showed that species tended to cluster together, though C. tropicalis clustered with C. albicans .
Abstract: Yeast isolates were seeded in agar plates and overlaid with ‘killer’ fungi. After incubation, zones of growth inhibition were scored. These results were combined with those of the isolate's sensitivity to 5-fluorocytosine, cupric sulphate and sodium arsenate, to generate a biotype score. Eighty isolates of Candida albicans were placed in 33 biotypes. Other yeast species including C. glabrata and Cryptococcus neoformans had somewhat different biotypes from those associated with C. albicans . Cluster analysis was applied to the data and showed that species tended to cluster together, though C. tropicalis clustered with C. albicans . Several clusters of C. albicans were found.