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Selective Medium (selective + medium)
Selected AbstractsSelective medium based on tyrosine metabolism for the isolation and enumeration of Brevibacillus brevis (Bacillus brevis)LETTERS IN APPLIED MICROBIOLOGY, Issue 5 2000S.G. Edwards Aims: To develop a selective medium for the enumeration of Brevibacillus brevis Nagano spores from soil and plant material. Methods and Results: Tyrosine agar was developed as a selective medium and compared with nutrient agar for the enumeration of B. brevis Nagano spores from sterile and non-sterile plant and soil extracts. Brevibacillus brevis Nagano colonies could be easily identified only on tyrosine agar due to their clear halo and distinct colony morphology. Identification was confirmed by thin layer chromatography of the antibiotic, gramicidin S, produced by this strain. Conclusions: Tyrosine agar was shown to be a suitable selective medium for the enumeration of B. brevis Nagano. Significance and impact of the study: The medium developed, tyrosine agar, can be used to monitor the population of the biological control agent, B. brevis Nagano, and will allow detailed studies within the crop environment. [source] Examination of Gould's modified S1 (mS1) selective medium and Angle's non-selective medium for describing the diversity of Pseudomonas spp. in soil and root environmentsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2003Sonia Tarnawski Abstract Studies on the diversity of environmental culturable Pseudomonas populations are dependent on the isolation procedure. This procedure includes the use of selective media which may influence the recovery of strains and thus the diversity described. In this study, we assessed the use of two agar isolation media for describing the diversity of soil- and root-inhabiting Pseudomonas associated with the perennial grass Molinia coerulea. A total of 382 Pseudomonas strains were recovered on either non-selective Angle's medium, or on Gould's modified S1 (mS1) Pseudomonas -selective medium. Their diversity was assessed by restriction analysis of PCR (polymerase chain reaction)-amplified 16S,23S rDNA internal transcript spacer sequences. The comparison of mS1- and Angle-recovered populations showed that the use of mS1 selective medium led to an underestimation of both Pseudomonas counts and diversity, especially in the soil environment. [source] Root recovery rates for Phytophthora cinnamomi and rate of symptom development from root rot on Abies fraseri trees over 7 yearsFOREST PATHOLOGY, Issue 1 2009G. J. Griffin Summary Phytophthora root rot on Abies fraseri trees was monitored from 2001 to 2007 within the disease front of a 12-year-old Virginia plantation where trees had been dying of the disease since 1994. After a slow increase in early foliage symptom development from July 2001 to September 2002, the frequency of A. fraseri trees with early symptoms accelerated for about 15 months. While the slow increase occurred during a 18.7% lower than normal rainfall period and the acceleration occurred during a 31.2% higher than normal rainfall period, the percentage of trees with early symptoms continued to increase during the mid-winter months (December,February) when the estimated mean minimum daily soil temperature (25 cm depth) was unfavourable (<10°C) to Phytophthora cinnamomi pathogenic activity. The time required for trees to progress from early foliage symptoms to completely dead foliage, from November 2000 to October 2007, was highly variable, ranging from 4 to 35 months. Root recovery rates for P. cinnamomi, assayed on a selective medium, were 6.4 times greater for symptomatic foliage trees than for asymptomatic foliage trees in this deep, silt-loam soil. Following an atypical cold period in February 2007, when the mean minimum daily soil temperature was 0.8°C, symptomatic roots yielded only a low level of germinable propagules of P. cinnamomi. Further, during an atypical midsummer in 2007 (June,August), when the soil water potential was at or below ,9 bars for 68 of 92 days, symptomatic roots yielded no germinable propagules of P. cinnamomi. Addition of thiophanate-methyl to the selective medium aided P. cinnamomi isolation by inhibiting many undesired pythiaceous colonies growing from symptomatic roots. [source] Mycobacterium avium ssp. paratuberculosis: its incidence, heat resistance and detection in milk and dairy productsINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 1 2001Irene R Grant Mycobacterium avium ssp. paratuberculosis (MAP) causes Johne's disease in cattle and other ruminants and has been implicated as a possible cause of Crohn's disease in humans. The organism gains access to raw milk directly through excretion into the milk within the udder, and indirectly through faecal contamination during milking. MAP has been shown to survive commercial pasteurization in naturally infected milk, even at the extended holding time of 25 s. Pasteurized milk must therefore be considered a vehicle of transmission of MAP to humans. Isolation methods for MAP from milk are problematical, chiefly because of the absence of a suitable selective medium. This makes food surveillance programs and research on this topic difficult. The MAP problem can be addressed in two main ways: by devising a milk-processing strategy that ensures the death of the organism; and/or strategies at farm level to prevent access of the organism into raw milk. Much of the research to date has been devoted to determining if a problem exists and, if so, the extent of the problem. Little has been directed at possible solutions. Given the current state of information on this topic and the potential consequences for the dairy industry, research is urgently needed so that a better understanding of the risks and the efficacy of possible processing solutions can be determined. [source] IMPROVED MEDIUM FOR DETECTION OF KLEBSIELLA IN POWDERED MILKJOURNAL OF FOOD SAFETY, Issue 1 2010HONG GAO ABSTRACT The selectivities to pathogenic Klebsiella strains of different isolation media were compared by known standard strains. The modified MacConkey-inositol-carbenicillin (MCIC) medium (Named MCIAC, MacConkey-inositol-adonitol-carbenicillin) supplemented with adonitol gave no false-negative colonies, and exhibited higher selectivity. MCIC and Simmons citrate agar with inositol (SCAI) media gave two false-negative colonies, respectively. These three media all gave two false-positive colonies, respectively. Salmonella Shigella medium gave four false-negative colonies and five false-positive colonies. Violet red bile glucose agar medium gave the most false-positive colonies, although it gave no false-negative colonies. One hundred samples of powdered milk were examined by MCIAC, MCIC and SCAI plates. The typical positive colonies were further identified using Vitek GNI Auto Microbic system and API 20E system. The results showed that the specificity of the MCIAC medium was higher than MCIC and SCAI media. PRACTICAL APPLICATIONS MacConkey-inositol-carbenicillin (MCIC) is the most commonly used selective medium for the detection of Klebsiella. But some inositol-nonfermenting Klebsiella strains would be missed when selected by this medium. We improved the MCIC medium by supplementing with 1% adonitol. The new modified medium (MacConkey-inositol-adonitol-carbenicillin, MCIAC) had advantages over other selective Klebsiella media in having a higher selectivity and an incubation time of only 16,24 h. MCIAC could be routinely used for pathogenic Klebsiella selection of powdered milk and other food samples. [source] Effects of ,-Glucan Addition to a Probiotic Containing YogurtJOURNAL OF FOOD SCIENCE, Issue 7 2007T. Vasiljevic ABSTRACT:, This study investigated the effects of addition of ,-glucan from 2 different cereal sources (oat and barley) on growth and metabolic activity of Bifidobacterium animalis ssp. lactis (Bb-12Ô) as determined by plating on a selective medium in yogurt during prolonged cold storage. These yogurt batches were compared to unsupplemented and inulin supplemented controls. All batches were also assessed for syneresis. Oat ,-glucan addition resulted in improved probiotic viability and stability comparable to that of inulin. It also enhanced lactic and propionic acid production. The barley ,-glucan addition suppressed proteolytic activity more than that from oat. These improvements were hindered by greater syneresis caused likely by thermodynamic incompatibility. Small amplitude oscillatory measurements of acidified model mixture of ,-glucan/skim milk solids showed formation of casein gel within the ,-glucan network. Binary mixtures of ,-glucan and skim milk solids had apparent pseudoplastic and non-Newtonian behavior governed mainly by ,-glucan contribution. Above critical concentrations, the mixtures underwent phase separation with the lower phase rich in protein. The phase diagram also showed that the addition of ,-glucan may be possible at or below 0.24 w/w%. [source] Use of Conventional Media and Thin Agar Layer Method for Recovery of Foodborne Pathogens from Pressure-treated Poultry ProductsJOURNAL OF FOOD SCIENCE, Issue 7 2003J. Yuste ABSTRACT: The recovery of 5 pathogens from minced chicken (MC) and liquid whole egg (LWE) was determined with tryptone soya agar (TSA), selective medium, and thin agar layer (TAL; selective medium overlaid with TSA) to evaluate high-pressure effects at 200, 300, 400, and 500 MPa for 1 and 5 min at 20 °C. At 400 MPa for 5 min, Escherichia coli inactivation was 4 log in MC and 5.5 log in LWE, whereas no Salmonella Typhimurium, Yersinia enterocolitica, or Listeria monocytogenes were detected in either product. Staphylococcus aureus was the most pressure-resistant. In general, counts on the 3 media were not different. The TAL method allows differentiation of the inoculated pathogens from background microbiota. [source] Survival and retention of the probiotic Lactobacillus casei LAFTI® L26 in the gastrointestinal tract of the mouseLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2007P. Su Abstract Aims:, This study aimed to develop methods for the detection of the probiotic Lactobacillus casei LAFTI® L26 (L26) from mouse faeces, and to determine the survival and retention time of L26 in the mouse gastrointestinal tract. Methods and Results:, A selective medium, de Man Rogosa Sharpe (MRS) + bromocresol green + vancomycin (MGV), was designed for the isolation and enumeration of L26 from faecal samples of mice. PCR primers were designed to confirm the identity of L26-like colonies on MGV. These primers did not produce PCR products from related organisms that grew on MGV. Following the administration of L26 to BALB/c mice, faecal samples were collected and analysed using the designed methods. Survival studies showed viable L26 cells to be present in the faeces of mice for >48 h. Conclusions:, Our results suggest that L26 is able to survive and be retained within the digestive tract of mice for at least 48 h following oral administration. Significance and Impact of the Study:, MGV allows effective recovery of L26 from the background microbiota, including lactobacilli of mice. PCR was used to confirm that L26-like colonies were correctly identified as L26. Given the long retention time of L26 in the gastrointestinal tract of mice, it would appear that this probiotic strain may survive in the human gastrointestinal tract. [source] Improved bioluminescent enzyme immunoassay for the rapid detection of Salmonella in chicken meat samplesLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2005S. Fukuda Abstract Aims:, To evaluate an improved bioluminescent enzyme immunoassay (BEIA) using biotinylated firefly luciferase for the rapid detection of Salmonella in naturally contaminated chicken meat samples. Methods and Results:, Capture agents and lipopolysaccharide (LPS) extraction reagents for Salmonella were investigated to improve the sensitivity of the BEIA. Also, the use of Oxoid SPRINT (Simple Pre-enrichment and Rapid Isolation New Technology) as a pre-enrichment and selective medium for 26-h BEIA detection of Salmonella in chicken meat samples was examined. The use of polymyxin B as a capture agent on solid support and 3-[(3-Cholamidopropyl) dimethylammonio] propanesulfonic acid (CHAPS) for extraction of the LPS facilitated sensitive detection of Salmonella. Of 120 chicken meat samples, 25 samples were positive using the improved BEIA with the SPRINT and 25 samples were positive using the SPRINT followed by the standard isolation methods. Conclusions:, The improved BEIA, in which polymxin B was used as a capture agent and CHAPS was used for extraction of the antigen, had a sensitivity of 96·0% and a specificity of 98·9% for the detection of Salmonella in chicken meat. Significance and Impact of the Study:, The improved BEIA combined with the SPRINT medium for the detection of Salmonella in chicken meat samples produced comparable results to the culture methods in 26 h. [source] Bifidobacterium -selective isolation and enumeration from chicken caeca by a modified oligosaccharide antibiotic-selective agar mediumLETTERS IN APPLIED MICROBIOLOGY, Issue 4 2005S.N. Thitaram Abstract Aims:, To determine the efficacy and selectivity of an acidified, antibiotic-selective, oligosaccharide-containing media for enumerating Bifidobacterium spp. from chicken caeca samples. Methods and Results:, Transoligosaccharide propionate agar medium (TOS) modified by addition of mupirocin (50 ,g ml,1) and glacial acetic acid (1%, v/v), did not inhibit the growth of bifidobacteria compared with the control media yet inhibited the growth of Lactobacillus acidophilus, Lactobacillus gallinarum, Lactobacillus helveticus and Streptococcus gordonii. Conclusions:, Addition of mupirocin (50 ,g ml,1) and glacial acetic acid (1%, v/v) to TOS (TOS-AM50), is an effective selective medium for isolation and enumeration of Bifidobacterium spp. from chicken caeca samples. Significance and Impact of the Study:, The development of an intestinal bifidobacteria-selective media contributes to the study of probiotics and prebiotics in poultry and potentially other species. [source] Evaluation of Chromocult® enterococci agar for the isolation and selective enumeration of Enterococcus spp. in broilersLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2005J.M. Miranda Abstract Aims:, To investigate the productivity and specificity of a new chromogenic enterococci selective medium (Chromocult® enterococci agar) recently developed by Merck. Methods and Results:, The study was carried out comparing Chromocult® enterococci agar with MRS agar (Merck), a basal lactic acid bacteria medium in current use. A total of 216 faecal samples from poultry were collected and enterococci populations were counted. Likewise, 100 randomly selected strains were identified for each medium. The differences found between the two media were analysed and discussed. Conclusions:, A good sensitivity of 98% was obtained for Chromocult® agar and all false-positive isolates obtained were identified as Leuconostoc spp. However significant differences (P < 0·01) were obtained between the enterococci species isolation rates identified from these two media, suggesting the poor growth of some species in Chromocult® enterococci agar. Viable counts of Enterococcus spp. obtained with MRS agar were significantly higher than those obtained with Chromocult® enterococci agar. Significance and Impact of the Study:, The use of chromogenic media for microbiological analysis is increasing. Independent studies are important to evaluate newly developed chromogenic media. [source] Selective medium based on tyrosine metabolism for the isolation and enumeration of Brevibacillus brevis (Bacillus brevis)LETTERS IN APPLIED MICROBIOLOGY, Issue 5 2000S.G. Edwards Aims: To develop a selective medium for the enumeration of Brevibacillus brevis Nagano spores from soil and plant material. Methods and Results: Tyrosine agar was developed as a selective medium and compared with nutrient agar for the enumeration of B. brevis Nagano spores from sterile and non-sterile plant and soil extracts. Brevibacillus brevis Nagano colonies could be easily identified only on tyrosine agar due to their clear halo and distinct colony morphology. Identification was confirmed by thin layer chromatography of the antibiotic, gramicidin S, produced by this strain. Conclusions: Tyrosine agar was shown to be a suitable selective medium for the enumeration of B. brevis Nagano. Significance and impact of the study: The medium developed, tyrosine agar, can be used to monitor the population of the biological control agent, B. brevis Nagano, and will allow detailed studies within the crop environment. [source] Phytophthora pinifolia sp. nov. associated with a serious needle disease of Pinus radiata in ChilePLANT PATHOLOGY, Issue 4 2008A. Durán During the course of the past three years, a new disease of Pinus radiata, referred to as ,Daño Foliar del Pino' (DFP) has appeared in the Arauco province of Chile and subsequently spread to other areas. The disease is typified by needle infections, exudation of resin at the bases of the needle brachyblasts and, in younger trees, necrotic lesions in the cambium, which eventually girdle the branches. The disease causes the death of young seedlings and mature trees can also succumb after a few years of successive infection, probably hastened by opportunistic fungi such as Diplodia pinea. Isolations on selective medium for Phytophthora spp. led to the consistent isolation of a Phytophthora sp. from needle tissue. DNA sequence comparisons for the ITS rDNA and cox II gene regions, and morphological observation showed that this oomycete represents a previously undescribed species for which the name Phytophthora pinifolia sp. nov. is provided. This new species is characterized by unbranched sporangiophores, and non-papillate, sub-globose to ovoid sporangia that are occasionally free from the sporangiophore with medium length pedicels. Despite using a number of oospore inducing techniques, oogonia/antheridia were not observed in isolates of P. pinifolia. Pathogenicity trials with P. pinifolia showed that it is pathogenic to P. radiata and causes rapid death of the succulent apical parts of young plants. Phytophthora pinifolia is the first Phytophthora known to be associated with needles and shoots of a Pinus sp. and its aerial habit is well matched with the occurrence and symptoms of DFP in Chile. [source] Host adaptation to potato and tomato within the US,1 clonal lineage of Phytophthora infestans in Uganda and KenyaPLANT PATHOLOGY, Issue 5 2000M. E. Vega-Sánchez Twenty isolates of Phytophthora infestans from potato and twenty-two from tomato, collected in Uganda and Kenya in 1995, were compared for dilocus allozyme genotype, mitochondrial DNA (mtDNA) haplotype, mating type and restriction fragment length polymorphism (RFLP) fingerprint using probe RG57. Based on RFLP fingerprint and mtDNA haplotype, all isolates were classified in the US,1 clonal lineage. Nonetheless, isolates from potato differed from isolates from tomato in several characteristics. Isolates from potato had the 86/100 glucose-6-phosphate isomerase (Gpi) genotype, while those from tomato were 100/100, which represents a variant of US,1 that had been identified previously as US,1.7. Furthermore, while pure cultures of the pathogen were acquired from infected potato leaflets by first growing the isolates on potato tuber slices, this approach failed with infected tomato tissue because the isolates grew poorly on this medium. Tomato isolates were eventually purified using a selective medium. Six isolates from each host were compared for the diameter of lesions they produced on three tomato and three potato cultivars in one or two detached-leaf assays (four isolates from the first test were repeated in the second). On potato leaflets, isolates from potato caused larger lesions than isolates from tomato. On tomato leaflets, isolates from that host caused larger lesions than did isolates from potato, but the difference was significant in only one test. The interaction between source of inoculum (potato or tomato) and inoculated host (potato or tomato) was significant in both tests. Isolates from tomato were highly biotrophic on tomato leaflets, producing little or no necrosis during the seven days following infection, even though abundant sporulation could be seen. In contrast, isolates from potato sporulated less abundantly on tomato leaflets and produced darkly pigmented lesions that were most visible on the adaxial side of the leaflets. Nonetheless, all isolates infected and sporulated on both hosts, indicating that host adaptation is not determined by an ability to cause disease but rather by quantitative differences in pathogenic fitness. Assessment of Gpi banding patterns, mtDNA haplotype and RFLP fingerprint of 39 isolates from potato collected in Uganda and Kenya in 1997 indicated that the population had not changed on this host. The population of P. infestans from Kenya and Uganda provides an interesting model for the study of quantitative host adaptation. [source] Pythium species associated with cavity spot on carrots in NorwayANNALS OF APPLIED BIOLOGY, Issue 2 2007A. Hermansen Abstract Carrot roots with cavity spot lesions from eight different counties in Norway were sampled and Pythium species were isolated on selective medium. Pythium spp. were characterised morphologically and by species-specific PCR. Laboratory experiments with inoculations of carrot roots were performed. A total of 130 isolates out of 230 Pythium -like isolates tested with PCR were identified as pathogenic species of Pythium. These were P. intermedium (29%), P. sulcatum (23%), P. sylvaticum (16%), P. violae (15%) and a possible new Pythium species designated P. ,vipa' (18%). There were some differences between geographical regions and ages of cavities regarding the frequency of the different species isolated. When rating sunken lesions in the laboratory inoculation experiments, P.,vipa' was the most aggressive and P. violae the least aggressive species. P. intermedium and P.,vipa' caused more discolouration of the infected carrot tissue than the other species. The importance of the different Pythium spp. as agents of cavity spot in Norway is discussed. [source] Scope and Mechanistic Insights into the Use of Tetradecyl(trihexyl)phosphonium Bistriflimide: A Remarkably Selective Ionic Liquid Solvent for Substitution ReactionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2006James McNulty Abstract A survey of substitution reactions conducted in a phosphonium bistriflimide ionic liquid is presented. The results demonstrate high selectivity favoring substitution over typically competitive elimination and solvolytic processes even when challenging secondary and tertiary electrophiles are employed. The first reports of Kornblum substitution reactions in an ionic liquid are described that proceed with very high chemoselectivity in favor of nitro over nitroso products and elimination side products. The structure,reactivity study indicates that these reactions proceed through a narrow spectrum of pathways ranging from straight SN2 to a preassociation pathway along a saddle point that approaches the SN1 limit. The barrier to the formation of dissociated carbocations is attributed to the structural features of this ionic liquid that favor intervention of the associated nucleophile over dissociation, also preventing cross over to E1 processes. The lack of any basic entity in the phosphonium bistriflimide ionic liquid appears to prevent any potential base-mediated elimination reactions, which makes this a highly selective medium for use in general substitution reactions. [source] Use of a reliable PCR assay for the detection of Neisseria gonorrhoeae in Peruvian patientsCLINICAL MICROBIOLOGY AND INFECTION, Issue 8 2006H. Mayta Abstract Neisseria gonorrhoeae is the most common sexually transmitted disease-causing bacterium worldwide. An in-house PCR assay targeting the carbamoyl-phosphate synthase subunit A (carA) gene was developed for the specific detection of N. gonorrhoeae in clinical specimens. Samples from 605 patients were cultured on selective medium and assayed by PCR in a double-blind fashion. Of 605 urethral/cervical samples analysed, 13 were PCR-positive, of which 11 were culture-positive. The PCR showed a sensitivity and specificity of 100% and 99.7% with these samples. PCR targeting the carA gene appears to be a reliable method for the detection of N. gonorrhoeae in clinical specimens. [source] | |||||||||||||