Showing papers on "Agar plate published in 1979"
TL;DR: A selective and differential agar medium that contains cycloserine, cefoxitin, fructose, and egg yolk (CCFA) was developed to facilitate the isolation of C. difficile from fecal specimens and was found to be the most sensitive and selective of these media for the recovery of the bacterium.
Abstract: Clostridium difficile is a recognized cause of pseudomembranous (antimicrobial agent-associated) colitis and may be one of the causes of antimicrobial agent-induced diarrhea. A selective and differential agar medium that contains cycloserine, cefoxitin, fructose, and egg yolk (CCFA) was developed to facilitate the isolation of C. difficile from fecal specimens. Quantitative cultures of 16 stock strains of C. difficile on this medium (and on a medium containing cycloserine, fructose, and egg yolk) yielded counts equivalent to those obtained on blood agar; other media selective for clostridia, including Clostrisel agar, reinforced clostridial agar plus 0.2% para-cresol, and egg yolk-neomycin agar (the latter was inoculated with cultures subjected to prior heat shocking), were also tested and found to be inhibitory to the growth of C. difficile. Of 28 fecal or colostomy effluent specimens cultured on the above media, 14 yielded C. difficile. CCFA was found to be the most sensitive and selective of these media for the recovery of C. difficile. Colonies of C. difficile growing on CCFA had distinctive morphological and fluorescent properties which were sufficient for presumptive identification. CCFA should provide a rapid method for the screening of fecal specimens from patients with antimicrobial agent-associated diarrhea or colitis for C. difficile.
624 citations
TL;DR: A new agar medium for isolation of Yersinia enterocolitica was formulated based on growth studies which defined an optimum basal, and the evaluation of selective chemical agents, dyes, and antibiotics, which provided quantitative recovery of 40 different strains of Y. enterocolItica.
Abstract: A new agar medium for isolation of Yersinia enterocolitica was formulated based on growth studies which defined an optimum basal, and the evaluation of selective chemical agents, dyes, and antibiotics. The final formulation, designated cefsulodin-irgasan-novobiocin(CIN) agar, provided quantitative recovery of 40 different strains of Y. enterocolitica in 24 h using incubation at 32 degrees C or with 48 h of incubation at 22 degrees C. The medium was highly selective, especially against Pseudomonas aeruginosa. Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. Colony morphology coupled with a differential reaction resulting from mannitol fermentation permitted discrimination of Y. enterocolitica from most of those Gram-negative bacteria that were able to grow on the medium. Recovery and selective characteristics of CIN agar were stable during storage at room temperature for 9 days. CIN agar gave a higher recovery of Y. enterocolitica from feces both direct and with cold enrichment (0.4/1.5%) than Salmonella-Shigella (0.0/0.7%) and MacConkey (0.0/0.9%) agars while significantly reducing the level of background organisms.
226 citations
TL;DR: In this paper, it was shown that SR, a H2-uptake-positive (Hup+) strain of R. japonicum, is capable of autotrophic growth with H2 as the energy source.
Abstract: Previous research from this laboratory has demonstrated CO2-fixing and H2-uptake capacities of certain strains of Rhizobium japonicum. In this report we have shown that SR, a H2-uptake-positive (Hup+) strain of R. japonicum, is capable of autotrophic growth with H2 as the energy source. Growth occurred on mineral salts/vitamins/Noble agar, mineral salts/vitamins liquid medium (0.27 μg of C as vitamins per ml), and in mineral salts liquid medium with no added vitamins when cultures were provided with NH4Cl and incubated in an atmosphere containing H2, CO2, O2, and N2. Little or no growth occurred when either H2 or CO2 was omitted from the atmosphere or when the culture was inoculated with SR3, a Hup- mutant of SR. Growth was measured by protein synthesis, fixed organic carbon, and increase in cell number in liquid cultures. The organism that grew autotrophically was verified as R. japonicum by (i) apparent purity on streak plates; (ii) retention of the double antibiotic resistance markers; and (iii) its capability to nodulate soybeans. H2- and CO2-supported growth was demonstrated for three additional Hup+ wild-type R. japonicum strains (USDA 136, 3I1b 6, and 3I1b 143), while three Hup- wild-type strains (USDA 120, 3I1b 144, and USDA 117) were incapable of growth on the Noble agar medium containing mineral salts/vitamins in the H2/CO2/O2/N2 atmosphere. This demonstrated capability of Hup+R. japonicum strains to grow autotrophically requires revision of current concepts regarding conditions for survival and competition of these bacteria in the soil and their relationships to other microorganisms.
133 citations
TL;DR: It has proved easy and convenient to detect 2-aminoacetophenone excretion by P. aeruginosa after 24 h of incubation on blood agar plates employing a fluorometric assay of ether extracts of the agar medium.
Abstract: A grapelike odor is often of diagnostic importance in detecting the growth of Pseudomonas aeruginosa in culture and in burn wounds. The compound responsible for the odor has been identified as 2-aminoacetophenone by mass spectroscopy. Although the grape odor is sometimes difficult to detect in culture media, gas chromatographic, fluorometric, and colorimetric methods can be utilized to assay 2-aminoacetophenone production in a variety of media. Its synthesis occurs relatively early in the growth cycle. It has proved easy and convenient to detect 2-aminoacetophenone excretion by P. aeruginosa after 24 h of incubation on blood agar plates employing a fluorometric assay of ether extracts of the agar medium.
107 citations
TL;DR: Scoring the agar plate before incubation under unidirectional light led to a rapid separation of gliding filamentous cyanobacteria from their contaminating bacteria, and Twenty strains were purified by the method.
Abstract: Scoring the agar plate before incubation under unidirectional light led to a rapid separation of gliding filamentous cyanobacteria from their contaminating bacteria. Twenty strains were purified by the method. Additionally, 13 axenic cyanobacterial strains were isolated from pour plates made after treatment of cyanobacterial cultures in tryptone-yeast extract-glucose broth with cycloserine in darkness to select for obligate photoautotrophs.
92 citations
Journal Article•
TL;DR: In this paper, an agar medium (PGUA agar) which permits the detection of bacteria with β-glucuronidase activity in mixed cultures was evaluated as a primary culture medium for clinical samples of urine.
Abstract: β‐glucuronidase activity is an exclusive characteristic of E. coli and some shigellae among Enterobacteriaceae and Vibrionaceae. An agar medium (PGUA agar) which permits the detection of bacteria with β‐glucuronidase activity in mixed cultures was evaluated as a primary culture medium for clinical samples of urine. The medium was selective for enterobacteria and yielded significantly higher recoveries than MacConkey agar. Based on the examination of 3,460 urine samples, it was found that the use of the PGUA agar has several advantages over conventional methods: 1) 94% of all E. coli cultures could be identified on the basis of their appearance on the primary plates; 2) The use of the PGUA method did not result in any misidentifications as compared to 1% of cultures misidentified by the conventional procedure; 3) Approximately one‐half of the urine samples which contained E. coli as the sole organism could be reported following the reading of primary culture plates; 4) The application of the PGUA medium resulted in a 46% reduction in the cost of media employed and a 67% reduction in the time required for the processing of urine samples.
62 citations
TL;DR: In maternal colonization studies, NPC broth proved superior to Todd-Hewitt broth containing nalidixic acid and gentamicin at concentrations employed in the previously described selective broth medium, and the NPC agar medium was useful for further purification of broth cultures and quantitative culture techniques.
Abstract: Problems encountered with currently recommended selective media for group B streptococci (GBS) (selective broth medium and CNA agar) prompted a searach for alternative culture methods in ongoing epidemiological studies. Previously recommended inhibitory agents were tested in vitro. Gentamicin, alone or in combination with nalidixic acid, proved inhibitory for many GBS strains. Among other agents tested, polymyxin was most complementary to the gram-negative spectrum of nalidixic acid, without compromising GBS growth. Crystal violet provided the simplest, most economical staphylococcal inhibitor. Broth and agar media, constituted with these three agents and designated NPC, were evaluated in vitro and in field studies. This investigation represents the first direct comparison of broth media containing inhibitory agents for the preferential isolation of GBS. In maternal colonization studies, NPC broth proved superior to Todd-Hewitt broth containing nalidixic acid and gentamicin at concentrations employed in the previously described selective broth medium (95% versus 59% recovery). Our comparisons were done without added sheep blood since GBS grow well in Todd-Hewitt broth. NPC broth proved more sensitive than NPC agar for detecting GBS colonization in newborns. The NPC agar medium was useful for further purification of broth cultures and quantitative culture techniques.
51 citations
TL;DR: Growth of Ureaplasma urealyticum isolates from clinical exudates and urine specimens was significantly improved by supplementation of a Urea Plasma differential agar medium by putrescine, designated medium A7B.
Abstract: Growth of Ureaplasma urealyticum isolates from clinical exudates and urine specimens was significantly improved by supplementation of a Ureaplasma differential agar medium by putrescine. The improved medium was designated medium A7B.
48 citations
TL;DR: Twenty-five isolates of nutritionally variant streptococci submitted to the Streptococcus Laboratory of the Center for Disease Control over a 2-year period were tested for growth requirements and for biochemical reactions, with overall agreement rate of 86.5% for key tests.
Abstract: Twenty-five isolates of nutritionally variant streptococci submitted to the Streptococcus Laboratory of the Center for Disease Control over a 2-year period were tested for growth requirements and for biochemical reactions. After they were recovered from storage in blood at -170 degrees C, all isolates grew within 48 h in both thioglycollate broth and Todd-Hewitt broth supplemented with 0.001% pyridoxal.HCl. They grew better in the latter, even though they all grew on unsupplemented infusion agar, anaerobe blood agar, and chopped meat-glucose medium. Biochemical patterns of the isolates resemble those of five viridans streptococcal species. Two isolates had patterns which did not resemble those of any viridans species. Biochemical reactions obtained with heart infusion broth base biochemicals and carbohydrate fermentation media compared favorably for an overall agreement rate of 86.5% for key tests. Lactic acid and acetic acid were the major fermentation products detected with gas-liquid chromatography.
48 citations
TL;DR: Several presumptive tests were evaluated for their effectiveness in differentiating streptococci and, when combined into a battery and the resulting reactions were interpreted as patterns, the overall presumptive identification rate was at least 97%.
Abstract: Several presumptive tests were evaluated for their effectiveness in differentiating streptococci. When the tests were combined into a battery and the resulting reactions were interpreted as patterns, the overall presumptive identification rate was at least 97%. We used the hemolytic reaction, susceptibility to bacitracin and sulfamethoxazole plus trimethoprim (1.25 micrograms plus 23.75 micrograms), and standard CAMP reactions on sheep blood Trypticase soy agar, and bile-esculin and 6.5% NaCl agar tolerance tests with incubation in candle extinction jars. Subsequently, 98.9% of the group A; 95.3% of the group B; 100% of the beta-hemolytic non-group A, B, or D; 92.3% of group D enterococcal; 100% of the group D non-enterococcal; and 92.8% of the viridans streptococci were presumptively identified. We then used the hemolytic reactions, susceptibility of bacitracin and sulfamethoxazole-plus-trimethoprim disks, CAMP disk reactions on sheep blood Trypticase soy agar and bile-esculin and 6.5% NaCl agar tolerance tests with incubation in normal atmosphere. Subsequently, 98.1% of the group A; 98.6% of the group B; 99.2% of the beta hemolytic non-group A, B, or D; 97.5% of the group D entercoccal; 97.6% of the group D non-entercoccal; and 92.4% of the viridans strains were presumptively identified.
41 citations
TL;DR: Sampling errors inherent in the procedure for subculturing broth tubes should be taken into consideration when interpreting results of individual tests, and replicate subcultures will improve the reliability of the colony counts.
Abstract: To determine the minimal lethal concentration of an antimicrobial agent, broth dilution tests may be performed and then a sample from each tube showing no visible growth may be subcultured onto a drug-free agar medium. By counting the number of viable cells recovered from each tube, the minimal concentration of drug required to kill 99.9% of the cells in the initial inoculum can be determined. Studies were undertaken to determine the circumstances under which false-negative tests could occur as a result of continued inhibition of growth by the antimicrobic carried over in the sample. Drug carryover did significantly reduce the number of viable cells recovered from broth containing relatively high concentrations of antimicrobic: the larger the sample, the greater the effect of drug carryover. The effect was minimal with samples of 10 microliter or less. Furthermore, the effect of drug carryover was reduced by spreading the sample over the surface of an agar medium. The relative precisions of four methods for performing subcultures with such small-volume samples were determined; coefficients of variation were 16-25%. Sampling errors inherent in the procedure for subculturing broth tubes should be taken into consideration when interpreting results of individual tests, and replicate subcultures will improve the reliability of the colony counts.
TL;DR: The properties and morphologies of phages that infect the industrially important clostridia, together with the nature of the damage and measures of control against phage contamination are described.
Abstract: Publisher Summary This chapter describes the properties and morphologies of phages that infect the industrially important clostridia, together with the nature of the damage and measures of control against phage contamination The chapter also includes information about the well-known phages and phagelike particles of C sporogenes, C botulinum, and C perfringens One of the assays used for the phages of acetone-butanol-producing clostridia—is the modified double-layer method In this method, a mixture of bacteria and phages is added to the bottom layer, covered with anaerobic agar medium containing sodium thioglycolate, and then incubated using the same procedure as for the cultivation of aerobes The growth of phages is best under conditions which are good for the growth of the host organisms In the case of C botulinum and C tetani, the plaque formation by phage infection is more difficult compared with C sporogenes, C perfringens, or C saccharoperbutylacetonicum, because—the former species do not produce an even lawn on the agar plates
TL;DR: An agar plate method for detection of hydrogen peroxide-producing bacteria using a non-carcinogenic chromogen is described.
Abstract: An agar plate method for detection of hydrogen peroxide-producing bacteria using a non-carcinogenic chromogen is described.
TL;DR: For several species of Clostridium, Bacteroides fragilis, Fusobacterium necrophorum, Veillonella alcalescens, and Pectinatus cerevisiiphilus, colony counts in the Lee tubes were comparable with those obtained in pour plates incubated in a BBL GasPak system and in anaerobic roll tubes.
Abstract: A new type of tube (the Lee tube) has been developed for use in the cultivation and enumeration of obligate anaerobes The Lee tube is a double-walled, screw-capped tube which allows the formation of a thin cylinder of agar medium between the two walls Anaerobiosis is achieved through deoxygenation of the deep cylinder of agar during sterilization, a minimum of head space, and use of a reducing agent to absorb oxygen introduced during the inoculation procedure For several species of Clostridium, Bacteroides fragilis, Fusobacterium necrophorum, Veillonella alcalescens, and Pectinatus cerevisiiphilus, colony counts of cultures in the Lee tubes were comparable with those obtained in pour plates incubated in a BBL GasPak system and in anaerobic roll tubes
TL;DR: In vitro malignant transformation of fetal rat keratinizing epidermal cells from inbred SD rats after benzo[a]pyrene (BP) treatment was analyzed from various biologic viewpoints and the appearance of stage III cells seemed to be the first key step in theirmalignant transformation.
Abstract: In vitro malignant transformation of fetal rat keratinizing epidermal cells from inbred SD rats after benzo[a]pyrene (BP) treatment was analyzed from various biologic viewpoints. BP treatment directly and indirectly effected changes in cell growth characteristics, i.e., temperature dependence for growth, in vitro keratinization, chromosome structure, and the ability to form colonies on plastic substrate, on 0.57% agar medium layer, and in 0.33% soft agar medium. BP-treated cells at 30 degrees C remained in the premalignant stages and showed shifts in chromosome structure toward the hypodiploid range and parakeratotic changes in their keratinization process. However, the cells failed to form colonies even on a plastic substrate. BP-treated cell lines that adapted to temperatures of 35 and 37.5 degrees C remained in the premalignant stages; however, they acquired the ability to form colonies on plastic substrates during subcultivation. Malignantly transformed colonies appeared in these cell lines. In vitro keratinization processes were classified into nearly normal (diffuse lamellar, focal lamellar, and parakeratotic), intermediate, and atypical subtypes (columnar, spherical, and single-cell type). Cells of atypical keratinization subtypes and some of the intermediate subtypes formed squamous cell carcinomas in syngeneic hosts. Malignantly transformed cells showed shifts in chromosome structure toward the hypotetraploid range and colony formation on the 0.57% agar medium layer. However, they failed to form colonies in 0.33% soft agar medium. With the use of changes in biologic characteristics of the cells as indicators, fetal rat keratinizing epidermal cells in culture were classified into five stages. The appearance of stage III cells seemed to be the first key step in their malignant transformation.
TL;DR: Detection of group A streptococci in primary throat cultures was compared by using aerobic and anerobic incubation with selective nonselective media to find those which had been stabbed at the time of inoculation.
Abstract: Detection of group A streptococci in primary throat cultures was compared by using aerobic and anerobic incubation with selective nonselective media. Sheep blood agar plates incubated anaerobically detected 98% of the group A streptococci, whereas aerobically incubated blood agar plates which had been stabbed at the time of inoculation detected only 63%. Blood agar plates containing sulfamethoxazole and trimethoprim (23.75 and 1.25 mirograms per ml, respectively) detected only 70% of group A streptocci when incubated aerobically and 84% when incubated anaerobically.
TL;DR: This chapter deals with those aspects of mutational and recombinational genetics that are important for creating and improving microbial cultures utilized in the production of commercial metabolites, such as antibiotics and amino acids.
Abstract: Publisher Summary This chapter deals with those aspects of mutational and recombinational genetics that are important for creating and improving microbial cultures utilized in the production of commercial metabolites, such as antibiotics and amino acids. In the programs designed to select mutants with increased metabolite yields, isolates are usually tested in the shake-flask cultures to reproduce the submerged growth conditions used in the industry. Initial testing on agar medium can aid in the selection of promising strains for subsequent analysis in shake flasks. A prerequisite for the study of the synthesis of antibiotics and their genetic control is the availability of mutants blocked at different steps in the biosynthetic pathway. Alterations in the morphology and pigmentation of colonies can be used for selecting such mutants. Basic information on the character and probable sites of genetic blocks in the biosynthetic pathway can be obtained by examining metabolic complementation in the mixed cultures of the pairs of blocked mutants under submerged conditions or by the agar method.
TL;DR: A nine-test system using multiple-inoculation agar plates for biotyping of Escherichia coli is described, which provides satisfactory differentiation among strains and is reproducible.
Abstract: A nine-test system using multiple-inoculation agar plates for biotyping of Escherichia coli is described. Testing of 959 strains resulted in 78 biotypes. On repeated testing, 96% of 182 strains had identical biotypes or differed by only one test. This system provides satisfactory differentiation among strains and is reproducible. Precise standardization of inoculum size is not required. Multiple inoculation allows time and cost-efficient testing of large numbers of strains.
TL;DR: An agar medium (medium V) was formulated to determine the minimal inhibitory concentrations (MICs) of antimicrobial agents for bacteria encountered in human periodontal pockets and the MICs of these antibiotics were essentially the same on both media when growth was quantitatively similar.
Abstract: An agar medium (medium V) was formulated to determine the minimal inhibitory concentrations (MICs) of antimicrobial agents for bacteria encountered in human periodontal pockets. The medium contained (per liter) Trypticase, 15 g; yeast extract, 5 g; sodium chloride, 5 g; glucose, 2 g; sodium pyruvate, 2 g; sodium formate, 1 g; sodium fumarate, 1.5 g; sodium succinate, 0.1 g; Tween 80, 0.25 ml; agar, 15 g; hemin, 5 mg; and menadione, 0.5 mg. The growth of 50 oral strains was compared on this and six other media which included: Wilkins-Chalgren agar, Schaedler agar, Brucella agar, Trypticase-soy blood agar, and Schaedler and Brucella agars supplemented with whole blood. Growth, for most strains, was greatest on medium V. Medium V was also compared with Wilkins-Chalgren agar, using the same oral strains, to determine the MICs of the following antibiotics: penicillin, tetracycline, chloramphenicol, clindamycin, and erythromycin. The MICs of these antibiotics were essentially the same on both media when growth was quantitatively similar.
TL;DR: Twelve methods for the demonstration of bacterial penicillinase production by strains of Haemophilus influenzae and Staphylococcus aureus are compared, and their suitability for routine clinical laboratory use is evaluated.
Abstract: Twelve methods for the demonstration of bacterial penicillinase production by strains of Haemophilus influenzae and Staphylococcus aureus are compared, and their suitability for routine clinical laboratory use is evaluated. The acidometric agar plate method is recommended.
TL;DR: The latex agglutination method, utilizing antibody-coated latex particles, was adapted for serogrouping of Neisseria meningitidis and serotyping of encapsulated Haemophilus influenzae strains from agar plates and was found to give more clear-cut results than conventional slide aggLutination.
Abstract: The latex agglutination method, utilizing antibody-coated latex particles, was adapted for serogrouping of Neisseria meningitidis and serotyping of encapsulated Haemophilus influenzae strains from agar plates. It was found to give more clear-cut results than conventional slide agglutination. A 100% agreement with the antiserum agar method was found for all strains isolated from blood or cerebrospinal fluid. Many meningococcal strains from nasopharyngeal carriers are autoagglutinable, but some of these gave a positive reaction with the group B latex reagent, although they were negative by the antiserum agar method. The latex agglutination method has several advantages over others: the lack of autoagglutination, easy performance, easy interpretation, and very low consumption of antisera.
TL;DR: The repair detection method effectively recovered the injured portion of the population of enterococci capable of growing on KF streptococcal agar and allowed enumeration of the injured cells, which might have remained undetected when selective medium in the most-probable-number method was used.
Abstract: The repair detection procedure of Speck et al. (Appl. Microbiol. 29:549-550, 1975) was adapted for the enumeration of coliforms, fecal coliforms, and enterococci in seafood and environmental samples. Samples were pour plated with Trypticase soy agar, followed by a 1- to 2-h incubation to effect repair; the plates were then overlaid with the selective medium and incubated. Violet red bile agar and an incubation temperature of 45 degrees C were used as the selective conditions for fecal coliforms, and KF streptococcal agar was used for the enumeration of enterococci. The method was more efficient than the standard most-probable-number method for fecal coliform enumeration and also allowed enumeration of the injured cells, which might have remained undetected when selective medium in the most-probable-number method was used. The repair detection method effectively recovered the injured portion of the population of enterococci capable of growing on KF streptococcal agar. The repair enumeration method was not suitable for coliforms in marine samples because associative marine bacteria mimicked coliforms in violet red bile agar plates incubated at 35 degrees C. The marine bacteria did not grow at 45 degrees C and therefore did not interfere with fecal coliform enumeration.
TL;DR: A new simple method for the preparation of a liquid medium containing rabbit serum for the propagation of Treponema hyodysenteriae and other porcine intestinal spirochaetes is described, which developed more rapidly and viable counts reached higher levels at 42 degrees C than at 37 degrees C.
TL;DR: Overall, the tandem agar plate method is a rapid and convenient approach contributing to the identification of S. aureus from foods.
Abstract: In optimizing previously reported coagulase agar media to obtain a rapid, reliable, and inexpensive coagulase test agar, variations in plasmas, pH, buffer system, fibrinogen, and fibrinolytic inhibitor were investigated. The agar with the following composition was determined best for the demonstration of coagulase production by Staphylococcus aureus: 25 ml of 15% bovine fibrinogen (fraction I, type I, citrated, Sigma Chemical Co.), 25 ml of rehydrated rabbit plasma (coagulase plasma ethylenediaminetetraacetic acid, Difco), 10.0 mg of soybean trypsin inhibitor (Schwarz/Mann), and 450 ml of brain heart infusion agar (Difco). In additional studies involving 7 different temperatures and 11 heating times, the thermal destruction of microbial nucleases on plate count agar and coagulase test agar was investigated. Heating the plates for 2.5 h at 65°C destroyed all heatlabile nucleases, but not thermonucleases of S. aureus. A tandem agar plate method for the identification of S. aureus was developed. Coagulase and thermonuclease activity of 50 colonies can be detected on a single agar plate. Suspect S. aureus colonies isolated on various selective media are transferred to coagulase test agar, the plates are incubated at 37°C for 18 h, and the coagulase reaction is recorded. The plates are then heated at 65°C for 2.5 h, overlaid with toluidine blue-metachromatic diffusion agar, and reincubated at 37°C for 3 h, and the thermonuclease reaction is recorded. Studies based on 88 enterotoxigenic S. aureus strains and 133 and 48 suspect S. aureus strains isolated from fresh salami mixtures on mannitol salt and tellurite-polymyxin-egg yolk agars, respectively, demonstrated 100% agreement between the tandem agar plate method and standard coagulase and thermonuclease tests. Overall, the tandem agar plate method is a rapid and convenient approach contributing to the identification of S. aureus from foods.
TL;DR: Beta-hemolytic streptococci, groups C, F, and G, are inhibited on the SXT-BA plates and were the primary cause of the higher false-positive rates on SBA and pour plate plus broth methods.
Abstract: We compared the selective blood agar medium of Gunn et al. (J. Clin. Microbiol. 5:650-655, 1977) which contains sulfamethoxazole plus trimethoprim (SXT-BA) to the conventional blood agar surface plate (SBA) and a modified blood agar pour plate plus broth method for the recovery of group A streptococci from throat swabs. The influence of CO(2) and ambient air incubation of the SXT-BA and SBA plates was also evaluated. A total of 696 throat swabs from symptomatic children were cultured simultaneously by the five methods and observed after overnight incubation; 204 positive cultures were detected overall. Recovery rates of each individual method were: SXT-BA (CO(2)), 90.7%; SXT-BA (air), 87.7%; pour plate plus broth, 83.3%; SBA (CO(2)), 79.4%; and SBA (air) 77%. Approximately one-half of the false-negative cultures in the SXT-BA (CO(2)) and SXT-BA (air) methods had colony counts of >/=10 to 100 colonies per plate. In contrast, for the SBA (CO(2)), SBA (air), and pour plate plus broth methods, approximately 70% of the false-negative cultures had colony counts of >/=10 to 100/plate. False-positive cultures obtained by the SXT-BA (CO(2)) and SXT-BA (air) methods were 11 and 12.7%, respectively-one-half as high as the rates obtained by the remaining methods. Beta-hemolytic streptococci, groups C, F, and G, are inhibited on the SXT-BA plates and were the primary cause of the higher false-positive rates on SBA and pour plate plus broth methods. An additional 3% positive cultures were obtained by incubating SXT-BA (CO(2)) plates up to 48 h before discarding as negative. We recommend either the SXT-BA (CO(2)) or the SXT-BA (air) method with up to 48 h of incubation for routine use in throat cultures.
TL;DR: Yersinia enterocolitica was easily identified in mixed cultures, even from inocula containing three times as many other Enterobacteriaceae organisms as Y. enterocolItica, with all strains having depressed colonies, while the other media showed lesser recoveries.
Abstract: A modified pectin agar medium was evaluated for the rapid isolation and presumptive identification of Yersinia enterocolitica . Of 118 isolates of Enterobacteriaceae tested, only the 13 Y. enterocolitica and the three Klebsiella oxytoca strains produced colonies that depressed and sank into the agar. Yersinia enterocolitica was also easily identified in mixed cultures, even from inocula containing three times as many other Enterobacteriaceae organisms as Y. enterocolitica . The recovery of Y. enterocolitica was evaluated on Mueller-Hinton, pectin, Hektoen enteric, xylose lysine desoxycholate, Salmonella- Shigella, and MacConkey agars. Compared with Mueller- Hinton agar, the pectin agar showed a 100% recovery of Y. enterocolitica , with all strains having depressed colonies, while the other media showed lesser recoveries of only 5 to 25%, with no other discriminating colonial characteristic.
TL;DR: Yeast extract, a component of Drosophilacell culture media, is shown to contain substances of high, intermediate, and low molecular weight, that are, respectively, essential, inhibitory, and stimulatory for colony formation in semisolid agar medium.
Abstract: Yeast extract, a component of Drosophilacell culture media, is shown to contain substances of high, intermediate, and low molecular weight, that are, respectively, essential, inhibitory, and stimulatory for colony formation in semisolid agar medium. Furthermore, it is shown that high concentrations of pyridoxal greatly increase the cloning efficiency of Drosophilacells. A cloning method with line Kc is described which routinely gives cloning efficiencies in excess of 20%.
TL;DR: Rhizobium japonicum 61-A-101 grew and fixed nitrogen more effectively onMedia containing an organic acid and a pentose sugar than on media containing only one of these carbon sources.
Abstract: Rhizobium japonicum 61-A-101 grew and fixed nitrogen more effectively on media containing an organic acid and a pentose sugar than on media containing only one of these carbon sources. Peak specific activities in the range 10–15 nmol C2H4 · h-1 · mg protein-1 were found for these organisms in a spot of growth about 1 cm diameter on agar surfaces exposed to air. Increasing concentrations of the organic acids (succinate or malonate) in a medium containing arabinose resulted in longer lasting activity. The inclusion of a third carbon source, glycerol, gave activity which remained at the maximum from about the 8 to the 18 day after inoculation although no growth of the bacteria occurs during the last 8 or 10 days. At low concentration of organic acid l-arabinose was a much better carbon source for supporting nitrogenase activity of these organisms that the d-form. Both organic acids affected the morphology of the bacteria. Higher concentrations, especially of malonate, gave swollen and distorted cells. When bacteria growing on organic acid-containing agar plates were suspended and plated after appropriate dilution on yeast extract — mannitolglycerol agar there was heterogeneity of colony form, with up to 90% microcolonies after growth on high malonate concentrations. The effects of malonate may be correlated with characteristics of the bacteroid form inside the nodule which contains relatively high concentrations of organic acids, especially malonate.
TL;DR: Counts of colonies that developed after 4 days on agar medium containing 0.3% xylan and preincubated rumen fluid were similar to counts of xylanolytic bacteria obtained when total culturable counts were multiplied by the percentage of isolates capable of producing acid from xylan.
Abstract: Counts of colonies that developed after 4 days on agar medium containing 03% xylan and preincubated rumen fluid were similar to counts of xylanolytic bacteria obtained when total culturable counts were multiplied by the percentage of isolates capable of producing acid from xylan Shortening the incubation period reduced the chance of including satellite colonies of non-xylanolytic organisms in the count Nearly all of the xylanolytic isolates irrespective of the medium from which they were isolated degraded and utilized xylan extensively The use of a culture medium containing a high concentration (3%) of xylan is also described The number of colonies capable of producing clearings in this medium was less than 10% of the total culturable counts Isolates from such colonies were shown to produce diffusible (extracellular) xylanases
TL;DR: No statistical differences were found in the recovery of group A streptococci from throat culture specimens after overnight incubation of blood agar plates in 5% CO2 compared with anaerobiosis.
Abstract: No statistical differences were found in the recovery of group A streptococci from throat culture specimens after overnight incubation of blood agar plates in 5% CO2 compared with anaerobiosis. Anaerobic incubation required many more subcultures and resulted in considerably greater technical time and expense.