Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AGAR”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1994

Effects of agars on determination of potency of polymyxin B sulfate by the agar plate diffusion method.

The effects of agars on the determination of the potency of polymyxin B sulfate by the agar plate diffusion method were investigated. The results showed that there were significant differences in the potency of polymyxin B sulfate between agars produced by different manufacturers. In order to investigate this phenomenon, two major components of polymyxin B sulfate, namely, the polymyxin B1 and B2 fractions, were isolated and purified by preparative high-pressure liquid chromatography, and the effects of agars on the potencies of these two components were individually examined. The results showed that there were significant differences in the relative potency of the B1 component versus that of the B2 component between the agar preparations produced by different manufacturers. On the basis of the relative potency of each of the components and the composition of the components, we developed a theoretical equation with which we could calculate the activity of polymyxin B sulfate on a certain agar. The values computed from the equation were consistent with those obtained from actual measurements. It was concluded that the effects of agars on the determination of polymyxin B sulfate activity will become evident only when the composition of the reference standard significantly differs from that of the samples. When the standard and samples have the same compositions, the sources of the agar preparation exert no effect on the determination of the potency by the agar plate diffusion method.

Agar↗
PubMed1973

Comparison of brilliant green agar and Hektoen enteric agar media in the isolation of salmonellae from food products.

Brilliant Green (BG) agar and Hektoen enteric (HE) agar media were compared for their efficiency in isolating salmonellae from various food products. Of the 11,226 food specimens examined, 1,662 (or 14.9%) yielded salmonellae. Of this number, 1,475 (88.7%) were recovered from BG agar and 1,315 (79.1%) were recovered from HE agar media. The results indicate that BG agar is more effective in isolating salmonellae from food products. A smaller subsidiary study showed HE agar to be more selective than BG agar. Four hundred ten specimens yielded 92 nonlactose-fermenting isolants other than salmonellae on BG agar and only 11 such isolants on HE agar.

Agar↗
PubMed1975

Superiority of MacConkey's agar over salmonella-shigella agar for isolation of Shigella dysenteriae type 1.

The efficiency of MacConkey's agar in the isolation of various types of Shigella was compared with that of salmonella-shigella (SS) agar during an extensive 18-month outbreak of disease caused by Shigella. In all, 1,580 isolates of Shigella were obtained from 12,307 rectal swab and fecal samples of patients with diarrhea and their contacts by direct plating onto MacConkey's and SS agars. Shigella dysenteriae type 1 and Shigella flexneri constituted 55 percent and 33 percent of all isolates, respectively, with a smaller number of Shigella boydii and Shigella sonnei. MacConkey's agar was superior to SS agar in the detection of S. dysenteriae type 1; 83 percent of the isolates were detectable on MacConkey's agar, compared with 40 percent on SS agar. In contrast, 84 percent of S. flexneri isolates were detectable on SS agar, compared with 51 percent on MacConkey's agar alone. These findings confirm that, for the culture of fecal specimens thought to contain S. dysenteriae type 1, one of the media used should be noninhibitory. Shigella was isolated at a consistently and significantly higher rate from fecal samples than from rectal swabs.

Bacteriological Techniques↗
PubMed1984

Glucose-sucrose-potassium tellurite-bacitracin agar, an alternative to mitis salivarius-bacitracin agar for enumeration of Streptococcus mutans.

An agar medium for selective recovery and enumeration of Streptococcus mutans was developed as an alternative to mitis salivarius-bacitracin (MSB) agar. Combinations of dyes, antibiotics, and tellurite were added to a nonselective medium which, because of its sucrose content, allowed easy recognition of S. mutans colonies. Candle jar incubation for 2 days, by comparison with anaerobic incubation, reduced background flora but did not diminish S. mutans recoveries from clinical samples. Quantitative comparisons were made of the simultaneous recoveries of a number of authentic S. mutans serotype representatives and fresh clinical isolates, using various glucose-sucrose-potassium tellurite-bacitracin (GSTB) formulations and mitis salivarius, MSB, and blood agars. Mitis salivarius counts were not detectably different from blood counts, but counts on MSB were distinctly lower. A formulation of the new medium containing 5% glucose 5% sucrose, 0.001% potassium tellurite, 0.3 U of bacitracin per ml (hence GSTB), and 2% agar gave recoveries nearly equal to those on mitis salivarius agar and much greater than those on MSB. The medium yielded readily recognized S. mutans colonies and facilitated detection of intracellular polysaccharide formers upon flooding with I2 reagent. Freshly isolated serotype c, E, and f colonies could often be distinguished from serotype d and g colonies, a distinction made reliable by testing for intracellular polysaccharide. A study of 300 salivary samples revealed GSTB to give significantly higher recoveries than MSB. About 72% of all samples were substantially underestimated for S. mutans with MSB, and 6.7% of samples were falsely negative for S. mutans with MSB. Recovery of background flora on GSTB was as low or lower than on MSB, and both types of agar could be stored for at least 9 weeks without notable change of selectivity. Thus, GSTB agar appears to be simple and reliable to use and requires no anaerobic incubation. Caution is voiced about interpretation of data previously reported which evaluated S. mutans on MSB agar.

Agar↗
PubMed1994

Agar disk diffusion (Bauer-Kirby) tests with various fastidious and nonfastidious reference (ATCC) strains: comparison of several agar media.

Several agar media (Mueller-Hinton agar, MHA; diagnostic sensitivity test agar, DSTA; Schaedler agar, SchA; Todd-Hewitt agar with added yeast extract, THYA; Wilkins-Chalgren agar, WCA) were compared using the Bauer-Kirby agar disk diffusion test against six nonfastidious quality control strains: Staphylococcus aureus ATCC 25923 and ATCC 29213, Escherichia coli ATCC 25922 and ATCC 35218, Pseudomonas aeruginosa ATCC 27853, and Enterococcus faecalis ATCC 29212. MHA, DSTA, and THYA yielded essentially comparable inhibition zones. However, WCA and SchA antagonized cotrimoxazole and aminoglycoside antibiotics; furthermore, SchA antagonized polymyxin B, and both WCA and SchA antagonized imipenem against the P. aeruginosa strain, but not against the E. coli strains. Sheep blood-MHA (Bl-MHA), WCA, THYA, and DSTA were examined with Streptococcus pyogenes ATCC 19615, Streptococcus agalactiae ATCC 13813, and Streptococcus pneumoniae ATCC 6306. In comparison with Bl-MHA, both WCA and THYA yielded comparable inhibition zones against S. pyogenes; DSTA afforded suboptimal growth. DSTA yielded larger inhibition zones with the majority of antimicrobial drugs against S. agalactiae, whereas WCA and THYA enhanced the activity of oxacillin and penicillin G against this strain. S. pneumoniae strain ATCC 6306 grew well on Bl-MHA, yielded suboptimal growth on WCA and faint growth on THYA, and failed to grow on DSTA. Chocolate-supplemented sheep blood-MHA (CHOC-MHA) was compared with Haemophilus test medium (HTM), WCA with added NAD, and THYA with added hematin and NAD against Haemophilus influenzae strains ATCC 35056 and ATCC 49247. The activities of doxycycline and rifampin were enhanced against both strains by HTM, WCA+NAD, and THYA+hematin+NAD. Only WCA+NAD antagonized cotrimoxazole against both H. influenzae strains, an effect due to thymidine; however, HTM antagonized cotrimoxazole against S. aureus ATCC 25923 and E. coli ATCC 25922. It was concluded that Bl-MHA performed best for beta-hemolytic streptococci quality control strains. Likewise, CHOC-MHA was optimal for the two H. influenzae strains used in this comparative agar disk diffusion study.

Agar↗
PubMed1977

Recovery of spores of Clostridium botulinum in yeast extract agar and pork infusion agar after heat treatment.

Yeast extract agar, pork infusion agar, and modifications of these media were used to recover heated Clostridium botulinum spores. The D- and z-values were determined. Two type A strains and one type B strain of C. botulinum were studied. In all cases the D-values were largest when the spores were recovered in yeast extract agar, compared to the D-values for spores recovered in pork infusion agar. The z-values for strains 62A and A16037 were largest when the spores were recovered in pork infusion agar. The addition of sodium bicarbonate and sodium thioglycolate to pork infusion agar resulted in D-values for C. botulinum 62A spores similar to those for the same spores recovered in yeast extract agar. The results suggest that sodium bicarbonate and sodium thioglycolate should be added to recovery media for heated C. botulinum spores to obtain maximum plate counts.

Agar↗
PubMed1968

A new plating medium for the isolation of enteric pathogens. II. Comparison of hektoen enteric agar with SS and EMB agar.

During this study, 2,855 stool specimens from patients at Cook County Hospital were cultured for enteric pathogens. Hektoen Enteric Agar (HE) was compared with E M B and S S Agars by replicate samplings with both direct and indirect methods. Shigella species were recovered more than twice as often on HE Agar as on S S Agar by both methods. With the direct method only, out of 98 Shigella isolated, 97 were isolated from HE Agar, 74 were recovered from E M B Agar, and 40 were found on S S Agar. In addition, HE yielded better isolation of Salmonella strains than did S S or E M B by either direct or indirect methods. The greater efficiency of HE medium is discussed with respect to colonial recognition of enteric pathogens.

Agar↗
PubMed1993

Comparison of Rambach agar, SM-ID medium, and Hektoen Enteric agar for primary isolation of non-typhi salmonellae from stool samples.

Stool samples (n = 504) were streaked simultaneously onto Rambach agar (R agar; E. Merck, Darmstadt, Germany), SM-ID medium (bioMérieux S.A., Montalieu-Vercieu, France), and Hektoen Enteric (HE) agar (BBL Becton-Dickinson, Baltimore, Md.) in order to evaluate the performances of the first two media in comparison with that of the well-established HE agar. Following overnight cultivation at 37 degrees C, 29 samples (5.8%) were positive for non-typhi salmonellae on at least one of the three media. Sensitivities and specificities were 69 and 98%, 79 and 85%, and 100 and 79% for R, SM-ID, and HE agars, respectively. On the basis of the poor sensitivities, R and SM-ID agars are not recommended as primary plating media when screening for non-typhi salmonellae. However, the high specificity of R agar may help to reduce the work load when this medium is used for plating after enrichment.

Agar↗
PubMedDate not supplied

Effects of a functional agar surface on in vitro dentinogenesis induced in proteolytically isolated, agar-coated dental papillae in rat mandibular incisors.

In an attempt to study the effects of a three-dimensional agar surface on in vitro dentinogenesis both in the growing end and in incisally cross-cut pulp, the possible expression of odontoblast phenotype was investigated morphologically, autoradiographically and immunohistochemically. Explants were incubated for 8 days. In the growing end, during the last 4 days, mitotic cells differentiated into [3H]-thymidine-labelled, tubular matrix-forming cells. In cross-cut pulp, however, during the first 4 days, mitotic cells differentiated into [3H]-thymidine-labelled, tubular matrix-forming cells. Electron microscopy demonstrated that, in both regions, tubular matrix-forming cells had characteristics similar to those of primary odontoblasts. When agar was incubated alone, exogenous fibronectin was deposited on it rapidly. After 12 h, endogenous fibronectin appeared on explant peripheral cells. Collagen and materials reacting positively to periodic acid-Schiff (PAS) were first interposed between agar and explant after 4 days. After 8 days, an inner immunonegative layer corresponding to materials reacting positively to PAS or toluidine blue and an outer immunopositive layer of fibronectin or collagen were visible adjacent to the rows of elongated columnar cells. In the presence of Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP), a competitive inhibitor of attachment of cells to fibronectin, explants became detached from the agar surface, and no dentinogenesis occurred. These results indicate that, when in contact with an agar surface that becomes modified by fibronectin and/or by a complex of fibronectin with deposited matrix, dental mesenchymal cells progressively differentiate into tubular matrix-forming cells. Possibly the functional agar surface has the important role of providing a foothold for cell attachment, which is the first step towards in vitro odontoblast differentiation. This system of inducing tubular matrix-forming cells constitutes a useful model for the study of in vitro dentinogenesis.

Agar↗
PubMedDate not supplied

[Gel-producing properties of exopolysaccharide acrylamide in composition with agar-agar].

A possibility to use a new polymer--exopolysaccharide acrylamide (EPAA)--for partial substitution of agar-agar in solid nutrient media in microbiology has been studied. It has been established than the EPAA in concentration 6.0-12.0 g/l with agar in concentration 10.0 g/l produce gel which is so strong as agar in concentration 15.0-20.0 g/l. Quality of gels produced depends an the method of EPAA mixing with agar. It has been shown that usage of EPAA in nutrient media does not affect growth, colony and cell morphology and biochemical properties of microorganisms. The use of EPAA to prepare nutrient media permits us to reduce expenditures for agar.

Acrylamide↗
PubMed1997

A comparison of EF-18 agar and modified brilliant green agar with lutensit for isolation of Salmonella from poultry samples.

Two selective plating media were compared to determine their performance in a three-step protocol for isolation of Salmonella from faecal, litter, and fluff samples. The enrichment protocol consisted of: 1) Preenrichment in buffered peptone water (BPW), 2) Selective enrichment in Rappaport-Vassiliadis broth, and 3) Plating onto EF-18 agar and BGA/L simultaneously. From a total of 1101 samples, Salmonella was isolated from 158, 157 of which were faecal samples. Thirty-one of these isolates were recovered on one medium only, 18 could not be found on BGA/L and 13 could not be found on EF-18 agar. The relative specificity and sensitivity of each plating agar was determined by enumeration of false-positive and false-negative reactions. EF-18 agar compared favourably with BGA/L, displaying a sensitivity of 0.92 as opposed to 0.89 for BGA/L, calculated for the "fecal samples" group only. The calculated specificities for each group of samples were likewise considerably higher for EF-18 agar (0.75-0.91) than for BGA/L (0.35-0.55). Though EF-18 agar is slightly more expensive than BGA/L, the routine use of the former may result in a considerable reduction in overall laboratory costs due to its superior selectivity. On the other hand the combination of the 2 media clearly would reduce the number of false negative results, with little extra cost.

Agar↗
PubMed1999

Comparison of selective broth medium plus neomycin-nalidixic acid agar and selective broth medium plus Columbia colistin-nalidixic acid agar for detection of group B streptococcal colonization in women.

The combination of neomycin-nalidixic acid (NNA) agar and a selective broth medium (SBM) has recently been shown to improve the sensitivity of screening cultures for group B streptococcal (GBS) carriage in women. Because of the relatively high cost of NNA agar, a study was initiated to determine whether Columbia colistin-nalidixic acid (CNA) agar would be an equally sensitive, more economical alternative. A total of 580 cervical-vaginal and/or rectal specimens submitted for detection of GBS were included in the study. Each was plated onto NNA and CNA agar and then inoculated into SBM. GBS were recovered from 95 of 580 (16.4%) specimens, including 61 isolates from CNA, 74 from NNA, 73 from the CNA-SMB combination, and 86 from the NNA-SMB tandem. Of those, 22 isolates were recovered on NNA but not CNA, 9 were cultured on CNA but not NNA, 52 were isolated on both media, and 12 were recovered from subcultures of SBM only. The overall sensitivity of CNA alone (64. 2%) was statistically significantly less than that of NNA agar (77. 9%), as was the sensitivity of combination of CNA plus SBM (76.8%) compared to that of NNA plus SBM (90.5%). Based on these findings, CNA should not be considered an acceptable alternative to NNA for the detection of GBS colonization in women despite potential cost savings.

Agar↗
PubMed1988

A comparison of disc agar diffusion and agar dilution for the detection of methicillin resistant staphylococci.

Ninety two consecutively occurring clinical isolates of Staphylococcus aureus and 71 coagulase negative staphylococci (CONS) were tested by disc agar diffusion (DAD) and agar dilution (Mueller Hinton agar with 4% sodium chloride and 6 mcg/ml oxacillin) for methicillin resistance. There were 6 S. aureus and 33 CONS which were resistant to oxacillin. Five discrepancies (CONS) occurred between the two methods, with all indicating susceptibility by DAD and resistance by agar dilution. Four discrepancies were resolved by minimal inhibitory concentration (MIC) tests. In two of the CONS, the MIC agreed with the DAD results, and in the other two, the MIC agreed with the agar dilution results. Results of this study indicate that DAD is an accurate and acceptable method of detecting methicillin resistance in staphylococci (especially S. aureus) at this institution.

Agar↗
PubMed1983

Improvement of human melanoma colony formation in soft agar using boiled instead of autoclaved agar.

The effect of agar sterilized by either boiling or autoclaving on human melanoma colony formation in soft agar was compared using cells from 17 biopsies of metastatic malignant melanoma. The frequency of colony formation was significantly increased for cells grown in boiled agar in 8 samples (47%), unchanged in 8 samples (47%), and decreased in only one sample (6%). There were increases in both cluster and colony formation for the melanomas which had augmented colony formation when grown in boiled agar. There was also qualitative morphological improvement, including rounder, smoother cells and less extracellular debris surrounding the colonies. These data suggest that melanoma colony formation is enhanced when cells are grown in agar which has been sterilized by boiling rather than autoclaving.

Agar↗
PubMed1982

Bird manure filtrate agar for the formation of the perfect state of Cryptococcus neoformans, Filobasidiella neoformans. A comparative study of the agars prepared from pigeon and canary manure.

An account is given to two pairs of C. neoformans strains on two different bird manure filtrate agars, i.e. pigeon manure filtrate and canary manure filtrate agar. Basidiospore formation was observed in both pairs after 3 d incubation at 26 degrees C on both media. 0.1% biphenyl in pigeon manure filtrate agar showed an inhibitory activity on the formation of the perfect state of the C. neoformans pairs tested. Concentrated pigeon manure filtrate allowed growth of the imperfect, however not of the perfect state of C. neoformans. On canary manure filtrate agar, a brown color effect (BCE) of the colonies of the C. neoformans strains was observed in addition to their formation of the perfect state. Except for a known self-fertile strain no self-fertility could be seen in 40 C. neoformans strains on pigeon manure filtrate agar. Attention is drawn to the risk of laboratory infection when handling the perfect state of C. neoformans.

Agar↗
PubMed1967

Agar-gel precipitin-inhibition test for coccidioidomycosis. I. Preliminary evaluation of the complement-fixation and agar-gel precipitin tests in the serodiagnosis of human coccidioidomycosis.

The agar-gel precipitin-inhibition serological test for coccidioidomycosis was a more sensitive indicator of Coccidioides immitis antibodies than the tube precipitin, the agar-gel immunodiffusion, in the complement-fixation tests in assaying monkey sera, whether these sera were from prechallenge-vaccinated or postchallenged animals. When applying this technique to the assay of human sera, an analogous finding generally persisted. However, some human sera were positive by the complement-fixation test and negative by the agar-gel precipitin-inhibition test. These sera were diffused in agar-gel against various coccidioidin complement-fixation, tube precipitin, and agar-gel precipitin-inhibition test antigens with essentially negative results.

Animals↗