Showing papers on "Agar plate published in 2014"
TL;DR: In this paper, the authors used a pure culture of Gemmatimonas aurantiaca T-27T and three representative sources of environmental samples, soil, sediment, and water, as inocula and compared colony counts between PT and PS agar plates.
Abstract: Microbiologists have been using agar growth medium for over 120 years. It revolutionized microbiology in the 1890s when microbiologists were seeking effective methods to isolate microorganisms, which led to the successful cultivation of microorganisms as single clones. But there has been a disparity between total cell counts and cultivable cell counts on plates, often referred to as the “great plate count anomaly,” that has long been a phenomenon that still remains unsolved. Here, we report that a common practice microbiologists have employed to prepare agar medium has a hidden pitfall: when phosphate was autoclaved together with agar to prepare solid growth media (PT medium), total colony counts were remarkably lower than those grown on agar plates in which phosphate and agar were separately autoclaved and mixed right before solidification (PS medium). We used a pure culture of Gemmatimonas aurantiaca T-27T and three representative sources of environmental samples, soil, sediment, and water, as inocula and compared colony counts between PT and PS agar plates. There were higher numbers of CFU on PS medium than on PT medium using G. aurantiaca or any of the environmental samples. Chemical analysis of PT agar plates suggested that hydrogen peroxide was contributing to growth inhibition. Comparison of 454 pyrosequences of the environmental samples to the isolates revealed that taxa grown on PS medium were more reflective of the original community structure than those grown on PT medium. Moreover, more hitherto-uncultivated microbes grew on PS than on PT medium.
165 citations
TL;DR: A high throughput liquid screening assay that uses robotic instrumentation to dispense a precise amount of methicillin resistant S. aureus and worms in 384-well assay plates, followed by automated microscopy and image analysis, which allows screening for anti-staphylococcal compounds that are not toxic to the host.
Abstract: Staphylococcus aureus, the leading cause of hospital-acquired infections in the United States, is also pathogenic to the model nematode Caenorhabditis elegans. The C. elegans-S. aureus infection model was previously carried out on solid agar plates where the bacteriovorous C. elegans feeds on a lawn of S. aureus. However, agar-based assays are not amenable to large scale screens for antibacterial compounds. We have developed a high throughput liquid screening assay that uses robotic instrumentation to dispense a precise amount of methicillin resistant S. aureus (MRSA) and worms in 384-well assay plates, followed by automated microscopy and image analysis. In validation of the liquid assay, an MRSA cell wall defective mutant, MW2ΔtarO, which is attenuated for killing in the agar-based assay, was found to be less virulent in the liquid assay. This robust assay with a Z’-factor consistently greater than 0.5 was utilized to screen the Biomol 4 compound library consisting of 640 small molecules with well characterized bioactivities. As proof of principle, 27 of the 30 clinically used antibiotics present in the library conferred increased C. elegans survival and were identified as hits in the screen. Surprisingly, the antihelminthic drug closantel was also identified as a hit in the screen. In further studies, we confirmed the anti-staphylococcal activity of closantel against vancomycin-resistant S. aureus isolates and other Gram-positive bacteria. The liquid C. elegans – S. aureus assay described here allows screening for anti-staphylococcal compounds that are not toxic to the host.
90 citations
TL;DR: Streptomyces philanthi RM-1-138, isolated from the rhizosphere soil of chili pepper in southern Thailand, was investigated for its antagonistic activity against phytopathogenic fungi.
74 citations
TL;DR: BARDOT could potentially be used as a screening tool during isolation of the most important STEC serovars on selective agar plates from food samples in less than 24 h.
Abstract: Background
Shiga-toxin producing Escherichia coli (STEC) have emerged as important foodborne pathogens, among which seven serogroups (O26, O45, O103, O111, O121, O145, O157) are most frequently implicated in human infection. The aim was to determine if a light scattering sensor can be used to rapidly identify the colonies of STEC serogroups on selective agar plates.
Methodology/Principal Findings
Initially, a total of 37 STEC strains representing seven serovars were grown on four different selective agar media, including sorbitol MacConkey (SMAC), Rainbow Agar O157, BBL CHROMagarO157, and R&F E. coli O157:H7, as well as nonselective Brain Heart Infusion agar. The colonies were scanned by an automated light scattering sensor, known as BARDOT (BActerial Rapid Detection using Optical scattering Technology), to acquire scatter patterns of STEC serogroups, and the scatter patterns were analyzed using an image classifier. Among all of the selective media tested, both SMAC and Rainbow provided the best differentiation results allowing multi-class classification of all serovars with an average accuracy of more than 90% after 10–12 h of growth, even though the colony appearance was indistinguishable at that early stage of growth. SMAC was chosen for exhaustive scatter image library development, and 36 additional strains of O157:H7 and 11 non-O157 serovars were examined, with each serogroup producing unique differential scatter patterns. Colony scatter images were also tested with samples derived from pure and mixed cultures, as well as experimentally inoculated food samples. BARDOT accurately detected O157 and O26 serovars from a mixed culture and also from inoculated lettuce and ground beef (10-h broth enrichment +12-h on-plate incubation) in the presence of natural background microbiota in less than 24 h.
Conclusions
BARDOT could potentially be used as a screening tool during isolation of the most important STEC serovars on selective agar plates from food samples in less than 24 h.
58 citations
TL;DR: Antioxidants have been shown to help the growth of anaerobic bacteria and six anaerobe species were able to grow aerobically in Schaedler agar tubes and agar plates with high doses of ascorbic acid and/or glutathione.
Abstract: Antioxidants have been shown to help the growth of anaerobic bacteria. We were able to grow six anaerobe species (including Fusobacterium necrophorum and Ruminococcus gravus) and seven aerobic species all aerobically in Schaedler agar tubes and agar plates with high doses of ascorbic acid and/or glutathione. This may deeply change strategies for culturing bacteria.
58 citations
TL;DR: Standard protocols for TLC and contact bioautography with a novel application to amino acid-fermenting bacteria are described and the method is applied to the separation of red clover phenolic compounds and their screening for activity against Clostridium sticklandii.
Abstract: A common screen for plant antimicrobial compounds consists of separating plant extracts by paper or thin-layer chromatography (PC or TLC), exposing the chromatograms to microbial suspensions (e.g. fungi or bacteria in broth or agar), allowing time for the microbes to grow in a humid environment, and visualizing zones with no microbial growth. The effectiveness of this screening method, known as bioautography, depends on both the quality of the chromatographic separation and the care taken with microbial culture conditions. This paper describes standard protocols for TLC and contact bioautography with a novel application to amino acid-fermenting bacteria. The extract is separated on flexible (aluminum-backed) silica TLC plates, and bands are visualized under ultraviolet (UV) light. Zones are cut out and incubated face down onto agar inoculated with the test microorganism. Inhibitory bands are visualized by staining the agar plates with tetrazolium red. The method is applied to the separation of red clover (Trifolium pratense cv. Kenland) phenolic compounds and their screening for activity against Clostridium sticklandii, a hyper ammonia-producing bacterium (HAB) that is native to the bovine rumen. The TLC methods apply to many types of plant extracts and other bacterial species (aerobic or anaerobic), as well as fungi, can be used as test organisms if culture conditions are modified to fit the growth requirements of the species.
46 citations
TL;DR: A disk-based potentiation test reliably identifies FR-GST producers and can be performed easily and will be advantageous in epidemiological surveys and infection control of fosfomycin-resistant bacteria in clinical settings.
Abstract: The number of reports concerning Escherichia coli clinical isolates that produce glutathione S-transferases responsible for fosfomycin resistance (FR-GSTs) has been increasing. We have developed a disk-based potentiation test in which FR-GST producers expand the growth inhibition zone around a Kirby-Bauer disk containing fosfomycin in combination with sodium phosphonoformate (PPF). PPF, an analog of fosfomycin, is a transition-state inhibitor of FosA(PA), a type of FR-GST from Pseudomonas aeruginosa. Considering its mechanism of action, PPF was expected to inhibit a variety of FR-GSTs. In the presence of PPF, zone enlargement around the disk containing fosfomycin was observed for FosA3-, FosA4-, and FosC2-producing E. coli clinical isolates. Moreover, the growth inhibition zone was remarkably enlarged when the Mueller-Hinton (MH) agar plate contained 25 μg/ml glucose-6-phosphate (G6P). When we retrospectively tested 12 fosfomycin-resistant (MIC, ≥256 μg/ml) E. coli clinical isolates from our hospital with the potentiation test, 6 FR-GST producers were positive phenotypically by potentiation disk and were positive for FR-GST genes: 5 harbored fosA3 and 1 harbored fosA4. To identify the production of FR-GSTs, we set the provisional cutoff value, 5-mm enlargement, by adding PPF to a fosfomycin disk on the MH agar plates containing G6P. Our disk-based potentiation test reliably identifies FR-GST producers and can be performed easily; therefore, it will be advantageous in epidemiological surveys and infection control of fosfomycin-resistant bacteria in clinical settings.
43 citations
TL;DR: Phylogenetic analysis based on 16S rRNA gene sequences indicated the novel bacterium, strain KA5–BT, belonged to the genus Steroidobacter in Gammaproteobacteria, but differed from its closest relative, Steroidsobacter denitrificans FST, at the species level with 96.5% similarity.
Abstract: An agar-degrading bacterium was isolated from soil collected in a vegetable cropping field. The growth of this isolate was enhanced by supplying culture supernatants of bacteria belonging to the order Rhizobiales. Phylogenetic analysis based on 16S rRNA gene sequences indicated the novel bacterium, strain KA5-B(T), belonged to the genus Steroidobacter in Gammaproteobacteria, but differed from its closest relative, Steroidobacter denitrificans FS(T), at the species level with 96.5% similarity. Strain KA5-B(T) was strictly aerobic, Gram-negative, non-motile, non-spore forming, and had a straight to slightly curved rod shape. Cytochrome oxidase and catalase activities were positive. The strain grew on media containing culture supernatants in a temperature range of 15-37°C and between pH 4.5 and 9.0, with optimal growth occurring at 30°C and pH 6.0-8.0. No growth occurred at 10 or 42°C or at NaCl concentrations more than 3% (w/v). The main cellular fatty acids were iso-C15:0, C16:1ω7c, and iso-C17:1ω9c. The main quinone was ubiquinone-8 and DNA G+C content was 62.9 mol%. In contrast, strain FS(T) was motile, did not grow on the agar plate, and its dominant cellular fatty acids were C15:0 and C17:1ω8c. Based on its phylogenetic and phenotypic properties, strain KA5-B(T) (JCM 18477(T) = KCTC 32107(T)) represents a novel species in genus Steroidobacter, for which the name Steroidobacter agariperforans sp. nov. is proposed.
42 citations
TL;DR: The prevalence of bacterial isolates in eye discharge was high in the study area and majority of isolates were gram-positive bacteria, which were resistant to frequently used antimicrobials.
Abstract: The type and pattern of organisms that cause ocular infection changes over time. Moreover, the causative organisms have developed increased drug resistance. Therefore, the aim of this study was to determine the prevalent bacterial agents of eye discharge and their drug susceptibility patterns to commonly used antimicrobial agents. A retrospective study was conducted at Gondar University Hospital, Northwest Ethiopia from September, 2009 to August, 2012. Culture and drug susceptibility test results of patients who had eye infections were taken for analysis. Eye discharge samples were cultured on MacConkey agar, blood agar and chocolate agar plates. A standard biochemical procedure was used for full identification of bacterial isolates. Antimicrobial susceptibility tests were done on Mueller-Hinton agar by using disk diffusion method. Data was entered and analyzed by using SPSS version 16 software. A total of 102 eye discharges were submitted for microbiological evaluation, of which (60.8%) had bacterial growth. The most frequently isolated bacterial isolates were gram-positive bacteria (74.2%). The predominant bacterial species isolated was Coagulase-negative staphylococci (27.4%) followed by S. aureus ( 21%). Within the age group of 1 day-2 years old, (66.1%) of bacteria were isolated. Most of the bacterial isolates were resistance to ampicilin (71%), amoxicilin (62.9%), erythromycin (43.5%), gentamicin (45.2%), penicillin (71%), trimethoprim-sulphamethoxazole (58.1%), and tetracycline (64.6%) while Ceftriaxon and Ciprofloxacin showed (75.8%) and (80%) susceptibility respectively. From the total bacterial isolates, (87.1%) were showed multi drug resistance (MDR) to two or more drugs. The prevalence of bacterial isolates in eye discharge was high in the study area and majority of isolates were gram-positive bacteria. Most of the bacterial isolates were resistant to frequently used antimicrobials. Therefore, drug susceptibility test is necessary before prescribing any antimicrobials.
42 citations
TL;DR: An inexpensive and straightforward method for identifying bacteria by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) directly from positive blood cultures using prewarmed agar plates is described.
Abstract: This study describes an inexpensive and straightforward method for identifying bacteria by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) directly from positive blood cultures using prewarmed agar plates. Different inoculation methods and incubation times were evaluated to determine the optimal conditions. The two methods using pelleted material from positive culture bottles performed best. In particular, the pellet streak method correctly identified 94% of the Gram negatives following 4 h of incubation and 98% of the Gram positives following 6 h of incubation.
38 citations
TL;DR: In this paper, the size, shape, and surface patterns of yeast colonies for various combinations of agar and sugar concentrations were characterized using both mathematical and physical models and found that the FLO11 gene constrains cells to grow near the agar surface, causing the formation of larger and more irregular colonies that undergo hierarchical wrinkling.
Abstract: Yeasts can form multicellular patterns as they expand on agar plates, a phenotype that requires a functional copy of the FLO11 gene. Although the biochemical and molecular requirements for such patterns have been examined, the mechanisms underlying their formation are not entirely clear. Here we develop quantitative methods to accurately characterize the size, shape, and surface patterns of yeast colonies for various combinations of agar and sugar concentrations. We combine these measurements with mathematical and physical models and find that FLO11 gene constrains cells to grow near the agar surface, causing the formation of larger and more irregular colonies that undergo hierarchical wrinkling. Head-to-head competition assays on agar plates indicate that two-dimensional constraint on the expansion of FLO11 wild type (FLO11) cells confers a fitness advantage over FLO11 knockout (flo11Δ) cells on the agar surface.
TL;DR: Vibrio harveyi is an opportunistic human pathogen that may cause gastroenteritis, severe necrotizing soft-tissue infections, and primary septicemia, with a potentially high rate of lethality, and is found to be resistant to cephalothin, vancomycin, ampicillin, cefepime,cefotetan, and streptomycin.
TL;DR: The enzyme efficiently removed the phenolic compounds from aqueous solution within few hours which indicated that tyrosinase enzyme produced by Streptomyces espinosus strain LK-4 can be potently used for the removal of phenol and phenolic compound from wastewater in industries.
Abstract: The present study was focused on screening and characterization of tyrosinase enzyme produced by marine actinobacteria and its application in phenolic compounds removal from aqueous solution. A total of 20 strains were isolated from marine sediment sample and screened for tyrosinase production by using skimmed milk agar medium. Among 20 isolates, two isolates LK-4 and LK-20 showed zone of hydrolysis and these were taken for secondary screening by using tyrosine agar medium. Based on the result of secondary screening LK-4 was selected for further analysis, such as tyrosinase assay, protein content and specific activity of the enzyme. The tyrosinase enzyme was produced in a SS medium and was partially purified by ammonium sulfate precipitation, dialysis and SDS PAGE. The isolate (LK-4) was identified as Streptomyces espinosus using 16S rRNA gene sequencing and named as “Streptomyces espinosus strain LK4 (KF806735)”. The tyrosinase enzyme was immobilized in sodium alginate which was applied to remove phenolic compounds from water. The enzyme efficiently removed the phenolic compounds from aqueous solution within few hours which indicated that tyrosinase enzyme produced by Streptomyces espinosus strain LK-4 can be potently used for the removal of phenol and phenolic compounds from wastewater in industries.
TL;DR: CHROM agar has the advantage of being rapid, simple and cost effective method as compared to conventional methods in speciation of Candida isolates, which helps in selecting the most appropriate antifungal agent for vulvovaginal candidiasis.
Abstract: Introduction: Vulvovaginal candidiasis is one of the most common infections seen in women. Materials and Methods: A total of 300 symptomatic women were studied. High vaginal swabs collected from each patient were processed by Gram stain, culture on Sabourauds dextrose agar and CHROM agar plates. Isolates were identified and speciated using conventional methods and by the color of the colonies on the CHROM agar. Antifungal susceptibility was performed by disc diffusion method for fluconazole (25 μg) and voriconazole (1 μg) discs as per Clinical and Laboratory Standards Institute (CLSI) guidelines. Results: Vulvovaginal candidiasis was found in 53 (17.7%) of cases. Gram stain was positive in 22 (41.41%) of culture positives. Speciation of isolates by conventional and CHROM agar methods showed similar results. C. albicans 35 (66.0%) was the most common species isolated followed by C. tropicalis 14 (26.4%), C. krusei 2 (3.8%), C. parapsilosis and C. glabrata in 1 (1.9%) case each. Sensitivity to fluconazole was found in 91.4% of C. albicans, 57.1% of C. tropicalis and 50.0% of C. krusei. Sensitivity to voriconazole was seen in 91.4% of C. albicans, 85.7% of C. tropicalis and 50.0% of C. krusei. C. parapsilosis and C. glabrata were found sensitive only to voriconazole. Conclusion: CHROM agar has the advantage of being rapid, simple and cost effective method as compared to conventional methods in speciation of Candida. Routine susceptibility testing of Candida isolates help in selecting the most appropriate antifungal agent for vulvovaginal candidiasis.
TL;DR: The activity of COL plus rifampicin (RIF) against clinical isolates of COL-resistant, carbapenemase-producing GNB, and seven patients infected with these isolates were treated with the combination successfully.
Abstract: Colistin (COL) is one of the few antimicrobials that retain activity against carbapenemase-producing Gram-negative bacteria (GNB). However, the emergence of COL resistance has renewed the use of combination therapy. The aim of this study was to determine the activity of COL plus rifampicin (RIF) against clinical isolates of COL-resistant, carbapenemase-producing GNB. We employed 36 COL-resistant carbapenemase-producing isolates (27 Klebsiella pneumoniae, 5 Serratia marcescens, and 4 Acinetobacter baumannii) belonging to 36 patients. E-test/agar dilution of all strains was performed with E-test strips of COL placed on agar plates with and without RIF. In 11 patients, the synergy was confirmed by time-kill studies. Synergy was detected in 34 isolates, whereas indifference was detected in two S. marcescens. The E-test/agar dilution method showed comparable results to the time-kill studies. Seven patients infected with these isolates (two meningitis, four sepsis, and one urinary tract infection) were treated with the combination successfully.
Journal Article•
TL;DR: The results indicate that biofilm formation causes enhanced resistance against antibiotics and metal salts in otherwise susceptible planktonic A. haemolyticus MMC 8.
Abstract: Background & objectives: Available literature shows paucity of reports describing antibiotic and metal resistance profile of biofilm forming clinical isolates of Acinetobacter haemolyticus. The present study was undertaken to evaluate the antibiotic and metal resistance profile of Indian clinical isolate of A. haemolyticus MMC 8 isolated from human pus sample in planktonic and biofilm form. Methods: Antibiotic susceptibility and minimum inhibitory concentration were determined employing broth and agar dilution techniques. Biofilm formation was evaluated quantitatively by microtiter plate method and variation in complex architecture was determined by scanning electron microscopy. Minimum biofilm inhibiting concentration was checked by Calgary biofilm device. Results: Planktonic A. haemolyticus MMC 8 was sensitive to 14 antibiotics, AgNO 3 and HgC1 2 resistant to streptomycin and intermediately resistant to netilmycin and kanamycin. MMC 8 exhibited temporal variation in amount and structure of biofilm. There was 32 - 4000 and 4 - 256 fold increase in antibiotic and metal salt concentration, respectively to inhibit biofilm over a period of 72 h as against susceptible planktonic counterparts. Total viable count in the range of 10 5 -10 6 cfu / ml was observed on plating minimum biofilm inhibiting concentration on Muller-Hinton Agar plate without antimicrobial agents. Biofilm forming cells were several folds more resistant to antibiotics and metal salts in comparison to planktonic cells. Presence of unaffected residual cell population indicated presence of persister cells. Interpretation & conclusions: The results indicate that biofilm formation causes enhanced resistance against antibiotics and metal salts in otherwise susceptible planktonic A. haemolyticus MMC 8.
TL;DR: For the first time, the alkane-degrading ability and alkB/alkM were detected in Rhizobium, Rhodobacter, Trichococcus, Micrococcus, Enterococcus and Bavariicoccus strains, and the alkM gene was detected in Firmicutes strains.
Abstract: In total, 435 pure bacterial strains were isolated from microtherm oil-production water from the Karamay Oilfield, Xinjiang, China, by using four media: oil-production water medium (Cai medium), oil-production water supplemented with mineral salt medium (CW medium), oil-production water supplemented with yeast extract medium (CY medium), and blood agar medium (X medium). The bacterial isolates were affiliated with 61 phylogenetic groups that belong to 32 genera in the phyla Actinobacteria, Firmicutes, and Proteobacteria. Except for the Rhizobium, Dietzia, and Pseudomonas strains that were isolated using all the four media, using different media led to the isolation of bacteria with different functions. Similarly, nonheme diiron alkane monooxygenase genes (alkB/alkM) also clustered according to the isolation medium. Among the bacterial strains, more than 24 % of the isolates could use n-hexadecane as the sole carbon source for growth. For the first time, the alkane-degrading ability and alkB/alkM were detected in Rhizobium, Rhodobacter, Trichococcus, Micrococcus, Enterococcus, and Bavariicoccus strains, and the alkM gene was detected in Firmicutes strains.
01 Jan 2014
TL;DR: CHROM agar is a convenient and rapid method of identification of Candida species even in resource poor settings and species other than C. albicans are gaining clinical significance.
Abstract: Candida spp especially non albicans Candida are increasingly being isolated from clinical specimens. The conventional methods of identification are time consuming and difficult to perform. The study was done to evaluate the performance of conventional identification method (phenotypic and biochemical) and commercially available chromogenic Candida speciation media (CHROM agar) for the identification of medically important yeast and yeast-like organisms in a routine clinical microbiology laboratory. A total of 60 yeast strains were included during the one and half years study period. The conventional methods used for speciation of yeast isolates were germ tube test, chlamydospore formation test on corn meal agar, sugar fermentation test and sugar assimilation test and were compared against chromogenic agar medium (CHROM agar). Candida albicans (51.6%) was the most common Candida species, followed by C. tropicalis (25%), C. krusei (16.6%) and C. glabrata (6.6%). Agreement between the conventional method and chromogenic methods was 96% for C. albicans, 100% for C. tropicalis, 100% for C. krusei and 100% C. glabrata. C. albicans was the most common single species isolated. However, species other than C. albicans are gaining clinical significance (48% of all isolates in the present study). CHROM agar is a convenient and rapid method of identification of Candida species even in resource poor settings.
TL;DR: Results of antibiotic resistance showed that all the strains were susceptible to penicillin, erythromycin and resistant to vancomycin, while most of strains were able to produce pleasant flavours in fermented milk and gave a good acceptance.
Abstract: In this study, nineteen Lactobacillus isolated from Algerian goat's milk, 13 belonging to L. plantarum, three to L. pentosus, two to L. rhamnosus and one to L. fermentum, were examined in vitro in order to be used as adjunct culture in dairy products. The strains were tested for their proteolytic activity, sensory and safety properties. Strains LbMS16 and LbMS21 L. plantarum and LbMF25 L. rhamnosus presented the highest proteolytic activity. All the tested lactobacilli were able to grow on MRS agar containing 0.5 and 1% (W/V) of oxgall, whereas none produced biogenic amine (BA) from the four tested amino acids and were resistant to pH 2.0 and 3.0, but some strains were able to grow at pH 3.5. None of examined strains were β-haemolytic when grown in hors blood agar. Result of antibiotic resistance showed that all the strains were susceptible to penicillin, erythromycin and resistant to vancomycin. Diacetyl production was observed for two strains of L. plantarum and one of L. rhamnosus. Most of strains were able to produce pleasant flavours in fermented milk and gave a good acceptance. According to these results, the strains LbMS16, LbMS21and LbMF25 could be good candidates to be used as adjunct culture, playing a probiotic role in dairy products manufacture in Algeria.
TL;DR: It has been shown that tested oils, used even at subMIC, exhibit significant activity reducing the presence/quantity of important C. albicans virulence factors.
Abstract: The influence of essential oils (EOs) used at sublethal level, on the presence and intensity of Candida albicans virulence factors was evaluated. Minimal inhibitory concentrations (MICs) of Lemon balm, Citronella, Geranium and Clove oils were established as 0.097% (v/v). Using the agar plates with substrates for proteases, phospholipases and hemolysins it was shown that C. albicans ATCC 10231 and C. albicans ATCC 90028 strains differed in the type and amount of enzymes produced. No significant difference in their total amount could be detected after pretreatment for 24 h with EOs at ½ MIC. However, the short-term (1 h) acting oils at MIC caused a statistically significant reduction in this activity. In the API ZYM test it was demonstrated that both strains exhibited activity of the same 9 out of 19 enzyme types and that EOs caused a significant decrease in the release of some of them. In the presence of subMIC of EOs, or when the fungus had previously been exposed to the MIC of oil, germ tubes formation was significantly and irreversibly reduced. Such C. albicans spotted on the Spider agar containing EOs at subMICs were unable to penetrate the agar. A significant decrease in the C. albicans adhesion to the fibroblast monolayer with respect to controls was also demonstrated when yeasts had been exposed to EOs at MIC (1 h) in liquid medium. Thus, it has been shown that tested oils, used even at subMIC, exhibit significant activity reducing the presence/quantity of important C. albicans virulence factors.
01 Jan 2014
TL;DR: A biosurfactant producing strain was isolated from soil sample obtained from a coconut oil mill and identified as Pseudomonas aeruginosa F23, based on physiological, biochemical tests and 16S rRNA sequence analysis as mentioned in this paper.
Abstract: A biosurfactant producing strain was isolated from soil sample obtained from a coconut oil mill and identified as Pseudomonas aeruginosa F23, based on physiological, biochemical tests and 16S rRNA sequence analysis. Primary screening for biosurfactant producer was carried out by observing hemolysis on superimposed blood agar, zone of clearance on Tributyrine agar and blue halo around the growth on N-cetyl- N, N, N-trimethyl ammonium bromide agar. Maximum biosurfactant yield was obtained in optimized SM medium containing 2% coconut oil and 0.3% potassium nitrate (C:N ratio 7:1) at pH 8 incubated at 30 o C under shaker conditions (120 rpm) for 96 h with 4% inoculum (0.8 OD 530nm ) of the isolate.The biosurfactant was partially purified using acetone and rotary vacuum evaporator and quantitatively estimated by anthrone assay, which was found out to be 2.8 g/L. The biosurfactant could reduce the surface tension upto 31 mN/m with 60% emulsification index in 36h. HPTLC analysis of the product demonstrated Rhamnose to be a sugar moiety and FT-IR results confirmed it to be rhamnolipid type of biosurfactant. It showed stability on exposure to high temperature (up to 100 o C) and also demonstrated antibacterial activity.
Journal Article•
TL;DR: In this article, two hundred thirty four fungal strains were isolated by baiting method, for their feather degradation and keratinase producing ability, and tested on solid milk agar plates and in submerged culture.
Abstract: Two hundred thirty four fungal strains were isolated by baiting method, for their feather degradation and keratinase
producing ability. Fungi were tested on solid milk agar plates and in submerged culture. Maximum clearing zone
was made by Chrysosporium indicum (7mm) on solid agar plates. The highest keratinase production was found in
case of Acremonium strictum (74.40Unit/mL & 124.72 Unit/ml in 8 & 12 day incubation respectively, while
Chrysosporium indicum 110.10U/mL and Chrysosporium tropicum 78.64U/mL was found next to it.
TL;DR: PCR based quantification system is a rapid and highly specific and sensitive tool for the quantification of EM with high sensitivity and specificity.
Abstract: Effective microorganism (EM) cultures have been applied in many research fields such as agriculture, environment and bioremediation. EM is a mixed culture of microorganisms including predominant populations of lactic acid bacteria and yeasts with smaller numbers of photosynthetic bacteria, actinomycetes and other types of microorganisms. Quantitative analysis of EM is requisite for the applications of EM, as its efficiency varies depending on the composition of its main genera of EM. In this study, Rhodobacter sphaeroides, Rhodopseudomonas palustris, Lactobacillus plantarum, and Saccharomyces cerevisiae, the main genera of EM were quantified by quantitative real time polymerase chain reaction, (qRT-PCR). By using selected specific primers, photosynthetic bacteria, lactic acid bacteria and yeast were quantified with high sensitivity and specificity. The ability of viable cell count by qRT-PCR was compared with agar plate cell count, showing linear relationship. Thus, PCR based quantification system is a rapid and highly specific and sensitive tool for the quantification of EM.
TL;DR: B Bolton agar and modified charcoal cefoperazone deoxycholate agar (mCCDA) exhibited higher sensitivity for Campylobacter spp.
TL;DR: From these results, it is clear that the Azotobacter sp.
Abstract: Azotobacter strains were isolated from paddy soils by serial dilution agar plate method. The colonies were glistening; smooth, slimy, brown to black in morphology on Jenson’s N-free agar plates and the cells were Gram- negative bacteria. Biochemically, they were positive for indole production, citrate, catalase and Voges Proskauer test. Further, Nif gene sequence results revealed the presence of seven Azotobacter species. The effect of 1, 3 and 5% pesticides concentration viz., pendimethalin, chloropyrifos, glyphosate and phorate on nitrogen fixation, indole acetic acid, gibberllic acid, phosphate solubilization and bioassay of Azotobacter sp. were studied. Among all the species, GVT-1 strain was found to fix nitrogen at a maximum of 30µgN2 ml-1 day-1, produced highest quantity gibberllic acid (10µg25ml-1) and able to solubilize the phosphate at the rate of 9.8cm by forming the halo zone which was supplemented with 5% phorate. Similarly, GVT-1 strain produced a highest amount of indole acetic acid (31.8µgml-1) in 5% pendimethalin. Further bioassay activities of GVT-1 strain found efficient in increasing the root, shoot length and vigor of the plant. From these results it is clear that the Azotobacter sp. not only produces plant growth promoting substances but is also resistant to different pesticides and is not affected by the bacterial activity.
TL;DR: The mean number of bacterial colonies was the lowest in the chlorhexidine group, followed by the Decapinol, Listerine, and the no rinse groups, Nonetheless, a statistically significant difference was found only in the case of Listersine.
Abstract: Purpose: This study assessed the effectiveness of three antimicrobial mouthrinses in reducing microbial growth on photostimulable phosphor (PSP) plates. Materials and Methods: Prior to performing a full-mouth radiographic survey (FMX), subjects were asked to rinse with one of the three test rinses (Listerine ® , Decapinol ® , or chlorhexidine oral rinse 0.12%) or to refrain from rinsing. Four PSP plates were sampled from each FMX through collection into sterile containers upon exiting the scanner. Flame-sterilized forceps were used to transfer the PSP plates onto blood agar plates (5% sheep blood agar). The blood agar plates were incubated at 37� C for up to 72 h. An environmental control blood agar plate was incubated with each batch. Additionally, for control, 25 gas-sterilized PSP plates were plated onto blood agar and analyzed. Results: The mean number of bacterial colonies per plate was the lowest in the chlorhexidine group, followed by the Decapinol, Listerine, and the no rinse negative control groups. Only the chlorhexidine and Listerine groups were significantly different (p=0.005). No growth was observed for the 25 gas-sterilized control plates or the environmental control blood agar plates. Conclusion: The mean number of bacterial colonies was the lowest in the chlorhexidine group, followed by the Decapinol, Listerine, and the no rinse groups. Nonetheless, a statistically significant difference was found only in the case of Listerine. Additional research is needed to test whether a higher concentration (0.2%) or longer exposure period (two consecutive 30 s rinse periods) would be helpful in reducing PSP plate contamination further with chlorhexidine. (Imaging Sci Dent 2014; 44: 149-54)
TL;DR: Results from this study indicate that fungal growth can be inhibited by exposure to ITCs, however the results observed are specific to the ITC structure and exposure concentration.
Abstract: This study aimed to examine the effects of seven different isothiocyanates against the growth and development of three important soil borne potato pathogens, (Colletotrichum coccodes, Rhizoctonia solani and Helminthosporium solani) The study was carried out using an agar diffusion assay The radial growth of fungal pathogens grown on agar containing different ITCs at a range of concentrations was compared to that of growth on control agar plates that did not contain ITCs Results varied depending on the specific isothiocyanate incorporated into the agar They ranged from those which showed a significant effect on fungal growth to those which appeared to have little or no effect Where a suppressive effect was observed, due to the presence of the isothiocyanate, fungal colony growth decreased as the concentration of the incorporated isothiocyanate increased Results from this study indicate that fungal growth can be inhibited by exposure to ITCs However the results observed are specific to the ITC structure and exposure concentration
TL;DR: The cooperative adaptation of subcultivated Bacillus cereus and Ketogulonicigenium vulgare significantly increased the productivity of 2-keto-L-gulonic acid, the precursor of vitamin C, and provided novel insights into the systems-level understanding of the cooperative adaptation between strains in synergistic consortium.
Abstract: The cooperative adaptation of subcultivated Bacillus cereus and Ketogulonicigenium vulgare significantly increased the productivity of 2-keto-L-gulonic acid, the precursor of vitamin C. The mechanism of cooperative adaptation of the serial subcultivated B. cereus and K. vulgare was investigated in this study by culturing the two strains orthogonally on agar plates. It was found that the swarming distance of B. cereus along the trace of K. vulgare on the plate decreased after 150 days' subcultivation. Metabolomic analysis on these co-cultured B. cereus and K. vulgare strains showed that their cooperative adaptation was accomplished by three key events: (i) the ability of nutrients (e.g., amino acids and purines) searching and intaking, and proteins biosynthesis is increased in the evolved B. cereus; (ii) the capability of protein degradation and amino acids transportation is enhanced in evolved K. vulgare; (iii) the evolved B. cereus was found to provide more nutrients (mostly amino acids and purines) to K. vulgare, thus strengthening the oxidation and energy generation of K. vulgare. Our results provided novel insights into the systems-level understanding of the cooperative adaptation between strains in synergistic consortium.
TL;DR: The present study evaluated the antimicrobial in vitro effects of the salivary proteins lactoferrin and lysozyme on microorganisms involved in the carious process, obtaining their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC).
Abstract: The present study evaluated the antimicrobial in vitro effects of the salivary proteins lactoferrin and lysozyme on microorganisms involved in the carious process, obtaining their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Streptococcus mutans (ATCC 25175) and Lactobacillus casei (ATCC 7469) were submitted to broth macrodilution of lysozyme at 80 mg/mL and lactoferrin at 200 mg/mL. The tubes were read in a spectrophotometer after they had been incubated at 37 °C for 18 h, in a carbon dioxide chamber, in order to read the MIC. A new subculture was carried on agar plates to obtain the MBC. The agar diffusion method was also tested, using BHI agar with 100 µL of the standardized microbial inocula. Filter-paper disks soaked in 10 µL of the solutions lactoferrin (200 µg/mL) and lysozyme (80 µg/mL) were placed on the agar surface. Inhibition halos were not observed on the plates, showing the absence of the antimicrobial effects of these proteins in this method. The bactericidal and bacteriostatic effects of lysozyme on L. casei were 50.3 mg/mL and 43.1 mg/mL respectively. The bactericidal and bacteriostatic effects on S. mutans were 68.5 mg/mL and 58.7 mg/mL. Lactoferrin did not induce any inhibitory effects on any microorganism, even in the concentration of 200 mg/mL. There was not a synergic antimicrobial effect of proteins, when they were tested together, even in the concentration of 42.8 mg/mL of lysozyme and 114 mg/mL of lactoferrin (the highest values evaluated). S. mutans and L. casei were only inhibited by lysozyme, not affected by lactoferrin and by the synergic use of both proteins.
TL;DR: In this paper, the authors further demonstrated the consequences of the addition of an increased concentration (6 mM) of H2O2 and further extended the investigation on such an oxidant's impact on the growth of Salmonella spp., Pseudomonas spp, and Bacillus spp.
Abstract: With a previous observation of Escherichia coli growth cessation with the supplementation of 3 mM hydrogen peroxide (H2O2) at the late log phase, the current study further demonstrated the consequences of the addition of an increased concentration (6 mM) of H2O2 and further extended the investigation on such an oxidant's impact on the growth of Salmonella spp., Pseudomonas spp., and Bacillus spp. Cell culturability was measured through the enumeration of colony-forming units (CFUs) on agar plates for up to 72 h. Subsequent changes in cell morphology and arrangements were monitored, and the cell viability was simultaneously retraced by spot tests. A sharp decline in the culturable cells of E. coli was observed after 48 h with a large mass of cell aggregates upon addition of H2O2, while Pseudomonas spp. lost viability after 36 h. Impaired morphology of such stressed cells was comparable to those of the untreated cells. Notably, Pseudomonas cells were more prone to oxidative damage compared to E. coli. In contrast, the impact of H2O2 was insignificant in the case of Salmonella spp. and Bacillus spp., suggestive of a stringent defense mechanism against oxidative stress.