Showing papers on "Agar plate published in 1975"
TL;DR: It is concluded that the bacterial production of methyl mercury may be a means of resistance and detoxification against mercurials in which inorganic Hg2+ is converted to organic form and secreted into the environment.
Abstract: Twenty-three Hg2+ resistant cultures were isolated from sediment of the Savannah River in Georgia; of these, 14 were gram-negative short rods belonging to the genera Escherichia and Enterobacter, six were gram-positive cocci (three Staphylococcus sp. and three Streptococcus sp.) and three were Bacillus sp. All the Escherichia, Enterobacter, and the Bacillus strain were more resistant to Hg2+ than the strains of staphylococci and streptococci. Adaptation using serial dilutions and concentration gradient agar plate techniques showed that it was possible to select a Hg2+-resistant strain from a parent culture identified as Enterobacter aerogenes. This culture resisted 1,200 μg of Hg2+ per ml of medium and produced methyl mercury from HgCl2, but was unable to convert Hg2+ to volatile elemental mercury (Hg0). Under constant aeration (i.e., submerged culture), slightly more methyl mercury was formed than in the absence of aeration. Production of methyl mercury was cyclic in nature and slightly decreased if DL-homocysteine was present in media, but increased with methyl-cobalamine. It is concluded that the bacterial production of methyl mercury may be a means of resistance and detoxification against mercurials in which inorganic Hg2+ is converted to organic form and secreted into the environment.
118 citations
TL;DR: The screening technique described here is termed replica printing and should be applicable not only to studies of phospholipid metabolism but also to nucleic acid and protein synthesis.
Abstract: A new method has been developed which permits the rapid screening of E. coli colonies for mutants with defective enzymes of phospholipid metabolism. In this procedure, a disc of filter paper is pressed down on an agar plate containing several hundred colonies of mutagen-treated cells, after which the paper is lifted off. In the process the colonies are transferred to the paper, giving rise to a replica print of the master plate. The few cells from each colony left on the master keep growing in the original pattern. The pattern of colonies is also retained on the filter paper, even after the cells are rendered permeable with lysozyme and EDTA. Colonies treated in this manner remain absorbed to the paper, where they can convert sn-(U-14-C)glycero-3-P to phosphatidyl(U-14-C)glycerophosphate, dependent on added CDP-diglyceride. Unrelated reactions of sn-(U-14-C)glycero-3-P that may obscure the synthesis of phosphatidyl-glycerophosphate are inhibited by the addition of reagents poisoning energy generation. The radioactive phospholipid that forms around each colony on the paper is precipitated in situ with trichloroacetic acid, and unreacted sn-(U-14-C)glycero-3-P is washed away. After autoradiography, the colonies on the filter paper are stained with Coomassie blue. When the autoradiogram is superimposed on the strained paper, mutants are identified as blue colonies lacking a black halo. With this method, 20,000 colonies were screened in several days. Four mutants were identified with low levels of CDP-diglyceride:snglycero-3-P phosphatidyl transferase (EC 2.7.8.5, GLYCEROL-PHOSPHATE PHOSPHATIDYLTRANSFERASE, PHOSPHATIDYLGLYCEROPHOSPHATE SYNTHETASE) IN EXTRACTS. With a similar assay, 10,000 additional colonies were screened for mutants with altered CDP-diglyceride:L-serine O-phosphatidyltransferase (EC 2.7.8.8, phosphatidylserine synthetase), and four strains were found in which the enzyme is thermolabile. The screening technique described here is termed replica printing and should be applicable not only to studies of phospholipid metabolism but also to nucleic acid and protein synthesis.
105 citations
TL;DR: An antiserum agar medium was evaluated to determine its usefulness and accuracy in the study of the prevalence of Haemophilus influenzae type b in the pharynx of infants and young children and the high intensity of pharyngeal colonization of siblings of children with HIB meningitis.
Abstract: An antiserum agar medium was found to provide a rapid, sensitive, and highly specific method for pharyngeal culture and quantitation of HIB.
98 citations
TL;DR: Higher numbers of lac-tobacilli were detected when plates were incubated in a system flushed with CO2 rather than in air, and differences were observed in biochemical characteristics of some of the L. acidophilus cultures from humans were lower, in most cases, than those from pigs and chickens.
Abstract: Lactobacilli in fecal material from humans, pigs, and chickens were enumerated on lactobacillus selective agar (LBS). In all samples, higher numbers of lactobacilli were detected when plates were incubated in a system flushed with CO2 rather than in air. Much higher numbers of bacteria from human feces were detected when the LBS agar plates were incubated anaerobically in a hydrogen-carbon dioxide atmosphere (GasPak) than when incubated in CO2. The bacteria from human feces isolated on LBS agar incubated anaerobically were predominately bifidobacteria. Cultures from all three sources isolated on LBS agar incubated under CO2 were lactobacilli, including Lactobacillus acidophilus. Differences were observed in biochemical characteristics of some of the L. acidophilus isolated from all three sources. Guanine plus cytosine base ratios of deoxyribonucleic acid isolated from L. acidophilus cultures from humans were lower, in most cases, than those from pigs and chickens.
89 citations
TL;DR: This article corrects the article on p. 537 in vol.
Abstract: Counts on a new, autoclave-sterilizable violet red bile (VRB-2) agar were compared with counts on freshly boiled VRB agar. Yields on VRB-2 agar averaged 217, 180, 130, and 112% of counts obtained on the control medium for samples of water, cottage cheese, frozen vegetables, and raw milk, respectively. The general principle used for the development of VRB-2 agar could be applied to many other kinds of selective plating media.
84 citations
TL;DR: TECHNIQUES now exist for obtaining clonal growth in semi-solid agar of mouse neutrophil, macrophage, eosinophil, erythropoietic and megakaryocytic colonies, and attempts were made to obtainClonal growth of mouse lymphoid cells in agar medium supplemented with 2-mercaptoethanol.
Abstract: TECHNIQUES now exist for obtaining clonal growth in semi-solid agar of mouse neutrophil, macrophage, eosinophil, erythropoietic and megakaryocytic colonies1–5. Previous attempts to obtain colony formation by mouse lymphoid cells, however, were unsuccessful and cultured lymphocytes died very quickly, even in the presence of known lymphocyte mitogens. Mercaptoethanol and related substances have been shown to increase lymphocyte proliferation in liquid cultures6 and colony formation in agar by mouse plasmacytoma cells7. Based on these observations, attempts were made to obtain clonal growth of mouse lymphoid cells in agar medium supplemented with 2-mercaptoethanol.
78 citations
TL;DR: It was concluded that migration of cells present in these rings was mainly due to a chemotactic response to glucose which served both as the attractant and the substrate, and Chemotaxis of S. aurantia toward glucose may be used as a selective factor in isolating this bacterium from natural environments.
Abstract: 1.
Seven strains of Spirochaeta aurantia were isolated from pond and swamp water by means of a selective technique which utilized the ability of these organisms to move through bacterial filters and to diffuse through agar media. Although most of the isolations were accomplished when enrichment media low in carbohydrates were used, all seven strains were found to be exclusively saccharolytic.
2.
The isolates could be divided into two groups on the basis of cell morophology: a loosely coiled group, and a tightly coiled group with markedly smaller wave length and wave amplitude. Spirochetes of the latter group possessed a slightly lower GC content in their DNA. The isolates were facultative anaerobes, synthesized carotenoid pigments which conferred an orange color to aerobic colonies, and utilized a variety of carbohydrates — but not amino acids — as energy sources. Exogenous thiamine was required by six isolates tested. riboflavin by four, and biotin by one. The major products of glucose fermentation were acetate, ethanol, CO2 and H2. Growth of the isolates was inhibited by a variety of antibiotics. Determinations of GC contents of DNA showed that strains of S. aurantia are phylogenetically distant from spirochetes classified in the genera Treponema and Leptospira.
3.
S. aurantia populations inoculated in the center of agar medium plates migrated in the form of growth rings toward the periphery of the plates. The rate of migration of glucoseutilizing rings was greatest at low glucose concentrations (e.g., 0.02 g/100 ml). It was concluded that migration of cells present in these rings was mainly due to a chemotactic response to glucose which served both as the attractant and the substrate. Chemotaxis of S. aurantia toward glucose may be used as a selective factor in isolating this bacterium from natural environments.
4.
The subspecific epithet stricta is proposed to recognize, taxonomically, the tightly coiled strains of S. aurantia.
71 citations
TL;DR: Despite routine subcultures of the broth media to chocolate blood agar within 24 h of inoculation and after 5 days of incubation, detection of fungemia was significantly improved by the use of a biphasic medium.
Abstract: In a retrospective study covering the period January 1972 to June 1974, recovery rates of bacteria and of fungi were generally equivalent with tryptic soy broth, Thiol, thioglycolate, and Columbia broth media (all under vacuum with carbon dioxide and sodium polyanetholesulfonate). An additional biphasic medium consisting of brain heart infusion broth and a brain heart infusion agar slant, which was inoculated only where fungal sepsis was suspected clinically, yielded significantly higher recovery rates of fungi. There were 29 instances of cultures with fungi in both the biphasic and broth media, 80 instances of cultures with fungi only in the biphasic medium, and no instances of fungi only in the broth media. The isolates were as follows: Candida albicans, 74; C. parapsilosis, 20; C. tropicalis, 16; Torulopsis glabrata, 18; Torulopsis sp., 1; Cryptococcus neoformans, 12; C. laurentii, 2; and Histoplasma capsulatum, 16. Despite routine subcultures of the broth media to chocolate blood agar within 24 h of inoculation and after 5 days of incubation, detection of fungemia was significantly improved by the use of a biphasic medium.
55 citations
TL;DR: A new antibiotic, fumaramidmycin, has been isolated from a streptomycete NR-7GGl which was characterized and named Streptomyces kurssanovii and shows an antimicrobial activity against both Gram-positive and Gram-negative bacteria.
Abstract: A new antibiotic, fumaramidmycin, has been isolated from a streptomycete NR-7GGl which was characterized and named Streptomyces kurssanovii. The strain produced the antibiotic only when grown on agar plates but not in the submerged culture broth, where the contact with the vegetative mycelia appears to cause the inactivation of the antibiotic. The antibiotic shows an antimicrobial activity against both Gram-positive and Gram-negative bacteria.
50 citations
TL;DR: From the results of this study, the Kanagawa hemolysis was interpreted as an expression of quantitative difference in hemolysin production, a conclusion that is clearly demonstrated on special blood agar of high salt content.
Abstract: In a study of the Kanagawa phenomenon of Vibrio parahaemolyticus, both Kanagawa-positive and -negative strains were found to produce hemolytic factors that could not be differentiated on Wagatsuma blood agar. The presence of fermentable carbohydrates in media containing high concentrations of NaCl promoted the growth of V. parahaemolyticus and resulted in a marked decrease in medium pH and increased hemolysin production. The Kanagawa hemolysis of test strains differed according to the carbohydrates added. Clearly defined Kanagawa hemolysis was observed in blood agars of high salt content, but the distinction was lost in media containing 3% NaCl. From the results of this study, the Kanagawa hemolysis was interpreted as an expression of quantitative difference in hemolysin production, a conclusion that is clearly demonstrated on special blood agar of high salt content.
46 citations
TL;DR: CR agars and to a certain extent gentamicin-containing agars show the distinct advantage of being much more inhibitory towards the psychrotrophic Gram negative rods that predominate in the associated flora of such foods.
Abstract: Oxytetracycline–glucose–yeast extract agar (OGYA), gentamicin–glucose–yeast extract agar (GGYA) with the antibiotic added separately or sterilized with the medium, chlortetracycline–Rose Bengal agar (CRA), chloramphenicol-streptomycin agar (PYA) and to a lesser extent, oxytetracycline–gentamicin–glucose–yeast extract agar (OGGYA) with or without Rose Bengal added, have been compared for the selective enumeration of moulds in foods. The results obtained from dried cereal products show that the media are almost equally productive and selective when applied to such foods, but Rose Bengal limits the size of mould colonies. When examining fresh proteinaceous foods, such as minced meat and chicken, CR agars and to a certain extent gentamicin-containing agars show the distinct advantage of being much more inhibitory towards the psychrotrophic Gram negative rods that predominate in the associated flora of such foods. Oxytetracycline–glucose–yeast extract agar lost its bacteriostatic properties when heavily challenged with proteinaceous substrates and/or incubated for longer periods at 37° or even at 25°. For such applications chloramphenicol was found to be the antibiotic of choice.
TL;DR: Evidence available is consistent with the hypothesis that growth enhancement of algae is related to the release of stimulating substances through bacterial hydrolysis of the agar, and it is suggested that V. anguillarum #19264 occurred on an enriched agar medium; the other bacteria yielded variable responses.
Abstract: SUMMARY
Investigations were conducted into the effect of 3 marine bacteria, Vibrio anguillarum #19264, V. anguillarum #19109, and Escherichia coli, on the growth of 10 phytoplakters. A disc method on agar plates was used to evaluate growth responses. Growth enhancement of all algae in the presence of V. anguillarum #19264 occurred on an enriched agar medium; the other bacteria yielded variable responses. Evidence available is consistent with the hypothesis that growth enhancement of algae is related to the release of stimulating substances through bacterial hydrolysis of the agar.
TL;DR: Several Bacillus strains from the rhizosphere of Ammophila arenaria appeared on ‘nitrogen-free’ agar plates and characterisation suggests that these strains are new nitrogen-fixing Bacillus species.
Abstract: Several Bacillus strains, from the rhizosphere of Ammophila arenaria, appeared on ‘nitrogen-free’ agar plates. They were able to grow in nitrogen-poor medium to which 0.1% yeast extract was added. Three of these bacilli were tested for their ability to fix nitrogen using the acetylene reduction assay. The C2H2-reducing activity was determined at 8-hour intervals during their growth cycle. C2H2 reduction (and accordingly N2 fixation) was greater under anaerobic than aerobic conditions. Additions of 0.1% CaCO3 significantly increased the C2H2-reducing activity under both conditions. Characterisation suggests that these strains are new nitrogen-fixing Bacillus species. re]19740121
TL;DR: A carbohydrate fermentation plate medium is described for rapid and reliable confirmation of Neisseria gonorrhoeae, N. meningitidis, and other NeISSeria species and provides rapid and accurate fermentation patterns for use in routine confirmation procedures for Neissaria species.
Abstract: A carbohydrate fermentation plate medium is described for rapid and reliable confirmation of Neisseria gonorrhoeae, N. meningitidis, and other Neisseria species. The medium is based on a modification of NYC (U.S. Patent 3,846,241) medium, originally designed for the isolation of pathogenic Neisseria (3). A total of 715 clinical isolates were tested for their carbohydrate fermentation reactions on the medium, in parallel with cystin-Trypticase agar medium. In 82% of the strains tested, results were in agreement on both media and 18% gave conflicting results. The NYC modification provides rapid and accurate fermentation patterns for use in routine confirmation procedures for Neisseria species.
TL;DR: A simple, inexpensive method is described for the bio-assay of herbicides using micro-algae growing on agar plates, suitable for bio-detection of herbicide residues, or toxicity studies on soil or aquatic pollutants.
Abstract: A simple, inexpensive method is described for the bio-assay of herbicides using micro-algae growing on agar plates. A result is obtainable in 2 days and the method is suitable for biodetection of herbicide residues, or toxicity studies on soil or aquatic pollutants.
TL;DR: The design, calibration, and operation of a source of controlled amounts of cyclic AMP (c-AMP) are described and the resulting concentration profiles are given as functions of distance and time.
TL;DR: This chapter describes a technique for obtaining colonies of most established mammalian cells on the surface of agar plates in the absence of overlay liquid medium, closely analogous to that for culture of bacteria.
Abstract: Publisher Summary This chapter describes a technique for obtaining colonies of most established mammalian cells on the surface of agar plates in the absence of overlay liquid medium. This technique is closely analogous to that for culture of bacteria. Agar plate culture has the following advantages: (1) it is easy to prepare agar plates and isolate clones, (2) the plating efficiency is comparable to that of already established cloning techniques, (3) it can be used for assay of transformation, and (4) it is applicable to Lederberg style replica plating. In the original replica plating technique of Lederberg, colonies growing on the master plate are imprinted on pile fabrics and then transferred to a series of replica plates. In a similar way, colonies of mammalian cells on an agar plate can be transferred to identical positions on replica plates. In our method, velveteen (cotton) or velvet (silk or synthetic fabric) are used for imprinting. A sterilized 15-cm square of fabric is placed, nap upward, on a cylindrical stainless steel support (8.5 cm in diameter for a 90-mm petri dish) and fixed firmly in place with a metal hoop. Master plate carrying 30-40 well isolated colonies on its surface is inverted over the fabric with slight digital pressure to transfer the colonies. Then, the fabric is used for imprinting replica-inocula on a series of replica plates by impression in the same way. The replica plates are incubated in a CO2-incubator for 1 week.
TL;DR: A simplified medium composed of only Mueller-Hinton medium plus supplement C (yeast autolysate and hematin) was used successfully for ampicillin susceptibility testing of 20 recent clinical isolates of H. influenzae, including six strains with confirmed ampiculin resistance.
Abstract: Recent reports of bona fide ampicillin resistance among strains of Haemophilus influenzae have emphasized the need for improved methods of susceptibility testing of clinical isolates. A simplified medium composed of only Mueller-Hinton medium plus supplement C (yeast autolysate and hematin) was used successfully for ampicillin susceptibility testing of 20 recent clinical isolates of H. influenzae , including six strains with confirmed ampicillin resistance. With this medium, susceptible strains were inhibited by less than 1 μg of ampicillin per ml, whereas resistant strains had minimal inhibitory concentrations of 8 μg or greater per ml. This medium can be used for either disk diffusion, tube dilution, or agar plate dilution methods of susceptibility testing. It has the practical advantage of simplicity of preparation and retains the light color and transparency of Mueller-Hinton medium. This medium can also be used for preparation of an inoculum suspension that can be adjusted to a standardized turbidity.
TL;DR: All six reference strains of Bacteroides species, 36 laboratory isolates conforming to this group, and individual strains of Escherichia coli, Proteus mirabilis, Salmonella typhimurium and Clostridum welchii produced a dense black pigment, identified as ferrus sulphide, when grown in cooked-meat media containing cystine and ferrous sulphate.
Abstract: All of six reference strains of Bacteroides species, 36 laboratory isolates conforming to this group, and individual strains of Escherichia coli, Proteus mirabilis, Salmonella typhimurium and Clostridium welchii produced a dense black pigment, identified as ferrous sulphide, when grown in cooked-meat media containing cysteine and ferrous sulphate. This was an indicator effect resulting from the production of H2S by the bacteria in the presence of ferrous ions and was unrelated to the characteristic pigment produced by strains of B. melaninogenicus when grown on blood agar. A pigment was extracted by ultrasonic disintegration of washed cells of three reference strains of B. melaninogenicus grown for 1 week in horse-blood broth and on human-blood agar. It was intracellular or cell-associated, soluble in water and had the spectrophotometric characteristics of a derivative of haemoglobin. No such pigment was extracted from strains of B. fragilis or B. necrophorus by similar procedures. Pigment production is a stable characteristic of those strains of Bacteroides called B. nzelaninogenicus and it is a significant property in the classification of the Bacteroides group. However, the pigment-producing strains are not a homogeneous species, and there were considerable differences between the resuIts of biochemical tests and antibiograms obtained with the three strains of B. meluninogenicus.
TL;DR: Morphological and biochemical characteristics of 33 isolates from 30 samples generally conform to those described for this organism in the literature, except for the production of acid from sucrose, lactose, and sorbitol.
Abstract: Vibro parahaemolyticus was isolated from soft-shell clams (Mya arenaria) taken from 10 different clamming areas on Cape Cod, Mass., during July and August 1972. Direct plating on thiosulfate-citrate-bile salts-sucrose agar was found to be superior to either direct plating on Vanderzant modified salt starch agar or enrichment with Trypticase soy broth containing 7% salt for isolation from clam samples. Morphological and biochemical characteristics of 33 isolates from 30 samples generally conform to those described for this organism in the literature, except for the production of acid from sucrose, lactose, and sorbitol. Six of the isolates were hemolytic on human blood agar plates, whereas all showed a negative Kanagawa phenomenon. Twenty of the 33 isolates reacted with pooled antisera to the K antigen; 15 of these reacted with 9 different specific K antisera, leaving 5 untypable. Ten of these 15 reacted with 4 different O antisera.
Journal Article•
TL;DR: In vitro cultivation is reported of Mycobacterium leprae on a medium based on hyaluronic acid with additional ingredients of yeast extract, bovine albumin and glycerin together with phosphate buffer to serve as culture plates.
Abstract: In vitro cultivation is reported of Mycobacterium leprae on a medium (designated LA-3) based on hyaluronic acid with additional ingredients of yeast extract, bovine albumin and glycerin together with phosphate buffer. The medium is also incorporated with agar or agarose (designated LA-3P) to serve as culture plates. Initial growth in LA-3 in test tubes required about six weeks but subsequently this was speeded up to about two weeks utilizing large quantities of media with aeration by shaking twice a day. Growth on LA-3P yields numerous small orange-yellow colonies in two to three weeks. Facets of the emerging aspects of the life cycle of M. leprae under cultivation are given preliminary report. The bases for the allegation of M. leprae identity of the cultured bacilli are essentially the following six determinations. 1. Pathologic and experimental determined rationale for the essential M. leprae nutrient requirement. 2. Several cultures having the same characteristics have been isolated from LL patients widely separate in time and by geography. 3. Failure of culture isolates to subculture on the usual media employed in the cultivation of mycobacteria at both 37 degrees C and room temperature. 4. 1 degree cultures in liquid medium successfully transferred to 2 degrees liquid medium and to 2 degrees agar medium plates. 5. Bacillary isolates and bacilli of 1 degree and 2 degrees liquid medium cultures all stain with pooled LL serum, FITC coupled, M. leprae specific antibody with which a broad range of other mycobacteria do not react. 6. M. lepraemurium also presents good growth on this medium.
TL;DR: Two strains of Phytophthora infestons (Mont.) de Bary, one resistant to chloramphenicol and the other to streptomycin, were isolated following treatment of zoospores with the mutagen N-methyl-N′-nitro-N-nitrosoguanidine (NTG).
Abstract: Two strains of Phytophthora infestons (Mont.) de Bary, one resistant to chloramphenicol and the other to streptomycin, were isolated following treatment of zoospores with the mutagen N-methyl-N′-nitro-N-nitrosoguanidine (NTG). A mutant dependent on streptomycin was later isolated as a single zoospore from the strain resistant to streptomycin. The mutants were stable and resembled their wild types in morphology and virulence. The resistant strains grew well and sporulated freely in the presence of high concentrations of antibiotics (1000 μg/ml in agar medium). The strain dependent on streptomycin required only 2 μg/ml of streptomycin for growth on solid media, but was able to grow in liquid medium in the absence of streptomycin. Both wild type and mutant strains were more sensitive to antibiotics when cultured in liquid media.
Journal Article•
TL;DR: Thirty pesticides commercially available in Hungary and three well-known chemical mutagens were applied to agar plate cultures of her+ and her- derivatives of Escherichia coli WP2 try- strain and N-Trichloro methylthio-1,2,3,6-tetrahydrophthalimide, dimethyl-3,2-dichlorovinyl-phosphate and N
Abstract: Thirty pesticides commercially available in Hungary and three well-known chemical mutagens were applied to agar plate cultures of her+ and her- derivatives of Escherichia coli WP2 try- strain. After incubation, the plates were examined for a relative increase in reverse mutation number. N-Trichloro methylthio-1,2,3,6-tetrahydrophthalimide, dimethyl-3,2-dichlorovinyl-phosphate and N-trichloro methylthiophyhalamide proved to have definite mutagenic activity.
TL;DR: An 85-year-old woman with the diagnosis of diabetic ketoacidosis developed septicemia during hospitalization and Cultures of the patient's blood revealed the presence of Gram-variable coccobacilli, later identified as Corynebacterium aquaticum, which should be considered for separation from related organisms.
Abstract: An 85-year-old woman with the diagnosis of diabetic ketoacidosis developed septicemia during hospitalization. Cultures of the patient's blood revealed the presence of Gram-variable coccobacilli, later identified as Corynebacterium aquaticum. The microorganisms grew aerobically on blood agar plates after incubation overnight. The colonies were convex, non-hemolytic and slightly yellow-pigmented. No growth was observed on MacConkey and endo agar plates. The organisms were catalase-positive, oxidase-negative, motile, and oxidized glucose and mannitol. The morphologic and biochemical properties of Corynebacterium aquaticum should be considered for separation from related organisms such as Listeria monocytogenes, Corynebacterium species and oxidative Gram-negative rods that do not grow on MacConkey medium (Flavobacterium spp.).
TL;DR: Penicillin enrichment and selection of biochemical mutants was performed on agar plates and there is an optimum penicillin exposure time for the greatest yield of a particular auxotroph.
Abstract: Penicillin enrichment and selection of biochemical mutants was performed on agar plates. With this technique, there is an optimum penicillin exposure time for the greatest yield of a particular auxotroph.
TL;DR: Through systematic investigation of several variables the agar plate assay for lyso enzyme was modified so that concentrations as low as 5μg egg white lysozyme per 100 ml of sample could be determined in 3 h.
Abstract: Through systematic investigation of several variables the agar plate assay for lysozyme was modified so that concentrations as low as 5μg egg white lysozyme per 100 ml of sample could be determined in 3 h. Plates were stained with 0.5 g buffalo black in 100 ml 7% acetic acid followed by destaining in 7% acetic acid until satisfactory contrast between clear zones of lysis and surrounding seeded agarose was obtained. Standard egg white lysozyme solutions remained stable for at least 7 days at −5 C. The best lyso-plate method included 1.0 g agarose with 0.1 g NaC1 in 100 ml of a pH 7.0 phosphate buffer seeded with 0.020 g Micrococcus lysodeikticus and incubation at 47 C for 3 h.
TL;DR: The determinations with immunofluorescence showed an overall linear relationship with those obtained by culturing on mitis-salivarius agar, and a few samples showed considerably higher values in fluorescence.
01 Dec 1975
TL;DR: The standard practice of using a single susceptibility disk for the antimicrobial combination Septra (trimethoprim/sulfamethoxazole) has been further justified by a direct measurement of the diffusion rates of each compound through agar medium.
Abstract: The standard practice of using a single susceptibility disk for the antimicrobial combination Septra (trimethoprim/sulfamethoxazole) has been further justified by a direct measurement of the diffusion rates of each compound through agar medium. [14C]trimethoprim and [35S]sulfamethoxazole, singly and in combination, were applied to blank susceptibility disks which were incubated on 4-inch (10.16-cm) agar plates (Mueller-Hinton medium) at 37 C. The migration of each compound from the disk and diffusion through agar were measured with time by determining the radioactivity in concentric zones extending from the origin. The two compounds diffuse with similar rates, maintaining approximately a 1:20 concentration ratio which is approximately the ratio of trimethoprim to sulfamethoxazole observed in plasma during treatment. The diffusion rate is independent of the presence of the other compound; greater than 95% of the radioactivity is transferred from the disk to the agar in 24 h.
TL;DR: The peptones derived from the enzymatic hydrolysis of cottonseed flour are sufficient to promote the rapid and luxuriant growth of a wide spectrum of aerobic bacteria without the addition of peptone from other sources.
Abstract: Enzymatic hydrolysates of various cottonseed flours were prepared with the proteolytic enzymes bromelain, HT-200, Pronase, and trypsin. The growth of various aerobic bacteria of clinical significance in these hydrolysates was compared to that obtained with a standard casein-soybean peptone culture medium, Trypticase soy. The generation times of the majority of bacteria grown in the bromelain cottonseed flour hydrolysate were shorter than that obtained with the standard control broth. A bromelain cottonseed flour hydrolysate agar preparation supported the growth of the bacteria comparably to that of the casein-soybean agar substrate. All the bacterial colonies were larger on the bromelain cottonseed flour hydrolysate blood agar medium than those grown on the control agar. The peptones derived from the enzymatic hydrolysis of cottonseed flour are sufficient to promote the rapid and luxuriant growth of a wide spectrum of aerobic bacteria without the addition of peptone from other sources. It is suggested that cottonseed flour peptones be utilized as a nutrient source in general-purpose media for the clinical microbiology laboratory.