|
| ||
|
|
||
Broth
Kinds of Broth Terms modified by Broth Selected AbstractsPROTEIN PROFILE CHANGES IN ACID ADAPTED LISTERIA MONOCYTOGENES EXHIBITING CROSS-PROTECTION AGAINST AN ACTIVATED LACTOPEROXIDASE SYSTEM IN TRYPTIC SOY BROTHJOURNAL OF FOOD SAFETY, Issue 1 2000SADHANA RAVISHANKAR ABSTRACT Foodborne pathogens often tolerate and survive environmental stress conditions including extreme acidity to varying degrees. One possible reason for this survival may be the production of protective stress proteins during acid shock (ASR) and/or tolerance (ATR) responses. The ASR and ATR of Listeria monocytogenes strains V7, V37 and CA in tryptic soy broth without dextrose acidified with lactic acid were studied. Possible cross-protection of acid adapted cells against an activated lactoperoxidase system was also determined. The strains were either directly challenged at pH 4.0 and 3.5 to study their ASR or initially adapted at pH 5.5 for the equivalent of 1 generation before challenging at pH 4.0 and 3.5 to study their ATR. Adapted and nonadapted cells were challenged at pH 4.5 with or without an activated lactoperoxidase system. In all cases viability was determined by enumeration over a period of 24 or 48 h after challenge and the production of stress proteins analyzed by 2-dimensional gel electrophoresis. While there were some differences in the survival responses for each strain, the acid adapted cells of each strain survived to a greater degree than nonadapted cells at both pH 4.0 (at least 10 fold at 24 h) and pH 3.5 (at least 1000 fold at 6 h) but not at pH 4.5. The acid adapted cells exposed to the lactoperoxidase system survived better (at least 5-fold) than their nonadapted counterparts for all 3 strains at 24 and 48 h. The 2-dimensional gel analysis for all 3 strains showed that the adapted and nonadapted cells underwent a change in their physiology, (at pH 4.0 compared to the control at pH 7.0; at pH 4.5 with the addition of lactoperoxidase system components) in that there was induction as well as repression of several proteins. [source] A STUDY ON SUITABILITY OF FOUR ENRICHMENT BROTHS FOR PCR-BASED DETECTION OF LISTERIA MONOCYTOGENES FROM RAW MEATJOURNAL OF FOOD SAFETY, Issue 1 2006J. BALAMURUGAN ABSTRACT Four enrichment broths were evaluated for their compatibility with the polymerase chain reaction (PCR) for detection of Listeria monocytogenes from raw meat after single-step enrichment. Standardized PCR protocols for listeriolysin O (hlyA) gene were used for the species-specific identification of L. monocytogenes. Four broths, namely, modified University of Vermont broth (MUVM), Listeria enrichment broth (LEB), Fraser broth (FB) and polymyxin, acriflavin, lithium chloride, ceftazidime, aesculin, mannitol, egg yolk broth (PALCAM) , were inoculated with L. monocytogenes. The enriched cultures were subjected for PCR. Similarly, meat samples were artificially spiked with various concentrations of L. monocytogenes, these spiked samples were enriched in the above-mentioned four broths and subjected to PCR to determine the medium that was most compatible for PCR-based detection of L. monocytogenes. The aliquots taken during different incubation periods were subjected to three different procedures for the concentration of the target organism for use in PCR. Results revealed that MUVM was better than other broths for the detection of L. monocytogenes by both PCR and cultural method; moreover, it was able to support the growth of as low as 10 cfu/g of meat. Concentration of the target organisms by centrifugation and washing with PCR buffer was the most suitable method for improving PCR performance for detection of L. monocytogenes. Goat (n = 67) and buffalo (n = 45) meat samples from local markets were also screened by both PCR and cultural method to validate the results obtained from the spiking studies. Both results were in agreement in spiking studies as well as screening of market meat samples. [source] Analysis of the role of bacterial endospore cortex structure in resistance properties and demonstration of its conservation amongst speciesJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2001A. Atrih Aims: The aim of this work was to compare the chemical structure of the spore cortex of a range of species, and to determine any correlation between cortex structure and spore resistance properties. Methods and Results: The fine chemical structure of the cortex of Bacillus subtilis, Bacillus megaterium, Bacillus cereus and Clostridium botulinum was examined by muropeptide analysis using reverse phase HPLC. There is a conserved basic structure between peptidoglycan of these species, with the only difference being the level of de -N -acetylation of an amino sugar. In order to determine if an alteration in cortex structure correlates with heat resistance properties, the peptidoglycan structure and properties of B. subtilis spores prepared under different conditions were compared. Peptidoglycan from spores prepared in Nutrient Broth (NB) showed reduction in single L -alanine substituted muramic acid to only 13·9% compared with 20·6% in CCY-grown spores. NB-prepared spores are also unstable, with 161-fold less heat resistance (60 min, 85°C) and 43 times less Mn2+ content than CCY-grown spores. Addition of MnCl2 to NB led to a peptidoglycan profile similar to CCY-grown spores, sevenfold more heat resistance (60 min, 85°C) and an 86-fold increase in Mn2+ content. Addition of CCY salts to NB led all parameters to be comparable with CCY-grown spore levels. Conclusions: It has been shown that peptidoglycan structure is conserved in four spore-forming bacteria. Also, spore heat resistance is multifactorial and cannot be accounted for by any single parameter. Significance and Impact of the Study: Endospores made by diverse species most likely have common mechanisms of heat resistance. However, the molecular basis for their resistance remains elusive. [source] Growth-induced changes in the proteome of Helicobacter pyloriELECTROPHORESIS, Issue 5-6 2006Christina Uwins Abstract Helicobacter pylori is a major human pathogen that is responsible for a number of gastrointestinal infections. We have used 2-DE to characterise protein synthesis in bacteria grown either on solid agar-based media or in each of two broth culture media (Brucella and brain heart infusion (BHI) broth). Significant differences were observed in the proteomes of bacteria grown either on agar-based or in broth media. Major changes in protein abundance were identified using principal component analysis (PCA), which delineated the profiles derived for the three key growth conditions (i.e. agar plates, Brucella and BHI broth). Proteins detected across the gel series were identified by peptide mass mapping and Edman sequencing. A number of proteins associated with protein synthesis in general as well as specific amino acid synthesis were depressed in broth-grown bacteria compared to plate-grown bacteria. A similar reduction was also observed in the abundance of proteins involved in detoxification. Two of the most abundant spots, identified as UreB and GroEL, in plate-grown bacteria showed a >140-fold drop in abundance in bacteria grown in Brucella broth compared to bacteria grown on agar plates. Two protein spots induced in bacteria grown in broth culture were both identified as glyceraldehyde 3-phosphate dehydrogenase based on their N -terminal amino acid sequences derived by Edman degradation. The underlying causes of the changes in the proteins abundance were not clear, but it was likely that a significant proportion of the changes were due to the alkaline pH of the broth culture media. [source] Optimization of culture conditions for glucose oxidase production by a Penicillium chrysogenum SRT 19 strainENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 1 2010Ragini G. Bodade Abstract The enzyme glucose oxidase (GOD) has been used for a variety of biotechnological applications in food and pharmaceutical industries. In this study, the optimization of extracellular GOD production was carried out in a Penicillium chrysogenum SRT 19 strain isolated from contaminated and decaying cheese samples. Maximum GOD production was attained at pH 6 and 20°C in fermentation broth after 72,h of incubation. The effects of metal ions and sugars were screened for the induction of higher GOD production. The results revealed that glucose and lactose give the highest production of enzyme (0.670 and 0.552,U/mL, respectively) as compared with other sugars (sucrose, cellulose, mannitol and fructose). Out of the seven metal ions studied, CaCO3 (1.123,U/mL) and FeSO4 (0.822,U/mL) act as modulators, while MgSO4 (0.535,U/mL), CuSO4 (0.498,U/mL), HgCl2 (0.476,U/mL), ZnSO4 (0.457,U/mL) and BaSO4 (0.422,U/mL) yield lower production. The study therefore suggests that a strain of P. chrysogenum SRT 19 can be used as a new strain for GOD production. [source] Production of Taxol fromPhyllosticta spinarum, an endophytic fungus ofCupressus sp.ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2008R. Senthil Kumaran Abstract Taxol production during the cultivation on a modified liquid and potato dextrose broth medium was indicated for the first time to occur in Phyllosticta spinarum, an endophytic fungus isolated from the needles of Cupressus sp. The presence of taxol in the fungal culture filtrate was confirmed by chromatographic and spectroscopic methods of analysis. The amount of taxol produced by this fungus was quantified by high performance liquid chromatography. The maximum amount of taxol production was obtained in this fungus when grown on M1D medium (235,,g/L) followed by PDB medium (125,,g/L). The results indicate that P.,spinarum is an excellent candidate for taxol production. The production rate was 4.7,×,103 -fold higher than that found in the culture broth of an earlier reported fungus, Taxomyces andreanae. The fungal taxol extracted also showed a strong cytotoxic activity in the in vitro culture of human cancer cells tested in an apoptotic assay. [source] A Combined Hydroxylation of 3-Cyanopyridine to 3-Cyano-6-hydroxypyridine and 6-Hydroxynicotinic Acid by Resting Cells of Comamonas testosteroni JA1 Grown on Nicotinic AcidENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2005S. Yuan Abstract A strain of Comamonas testosteroni,JA1 known for its capacity to hydroxylate 3-cyanopyridine to 3-cyano-6-hydroxypyridine was found to be also capable to hydroxylate nicotinic acid at a higher rate. In the course of the induced cultivation the forming 6-hydroxynicotinic acid was degraded either slightly, in the presence of nicotinic acid in the medium, or faster, in the absence of nicotinic acid. In a combined process of hydroxylation of nicotinic acid by growing culture and hydroxylation of 3-cyanopyridine by resting cells of Comamonas testosteroni,JA1, not only an additional amount of 50.38,g of solid 6-hydroxynicotinic acid was produced from 1,L of cultivation broth with a 99.97,% molar conversion yield, but also the yield of 3-cyano-6-hydroxypyridine produced was more than doubled. This can be compared to that of the resting cells from the induced cultivation broth where within 8,h an amount of 5.77,g of solid 3-cyano-6-hydroxypyridine was produced by resting cells from 1,L of the cultivation broth. This also was superior to 4.39,g/L of cultivation broth of resting cells reported in the literature. [source] Evaluation of in vitro properties of di-tri-octahedral smectite on clostridial toxins and growthEQUINE VETERINARY JOURNAL, Issue 7 2003J. S. Weese Summary Reasons for performing study: Clostridial colitis and endotoxaemia of intestinal origin are significant causes of morbidity and mortality in horses. Intestinal adsorbents are available for treatment of these conditions; however, little information exists supporting their use. Objectives: To evaluate the ability of di-tri-octahedral smectite to bind to Clostridium difficile toxins A and B, C. perfringens enterotoxin and endotoxin, inhibit clostridial growth and the actions of metronidazole in vitro. Methods: Clostridium difficile toxins, C. perfringens enterotoxin and endotoxin were mixed with serial dilutions of di-tri-octahedral smectite, then tested for the presence of clostridial toxins or endotoxin using commercial tests. Serial dilutions of smectite were tested for the ability to inhibit growth of C. perfringens in culture broth, and to interfere with the effect of metronidazole on growth of C. perfringens in culture broth. Results: Clostridium difficile toxins A and B, and C. perfringens enterotoxin were completely bound at dilutions of 1:2 to 1:16. Partial binding of C. difficile toxins occurred at dilutions up to 1:256 while partial binding of C. perfringens enterotoxin occurred up to a dilution of 1:128. Greater than 99% binding of endotoxin occurred with dilutions 1:2 to 1:32. No inhibition of growth of C. difficile or C. perfringens was present at any dilution, and there was no effect on the action of metronidazole. Conclusions: Di-tri-octahedral smectite possesses the ability to bind C. difficile toxins A and B, C. perfringens enterotoxin and endotoxin in vivo while having no effect on bacterial growth or the action of metronidazole. Potential relevance: In vivo studies are required to determine whether di-tri-octahedral smectite might be a useful adjunctive treatment of clostridial colifis and endotoxaemia in horses. [source] Flow cytometric analysis of the localization of Helicobacter pylori antigens during different growth phasesFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2001Kristina Blom Abstract Previous studies on the localization of several different Helicobacter pylori antigens have been contradictory. We have therefore examined by using both one- and two-color flow cytometry (FCM), immunofluorescence (IF), and immunoelectron microscopy (IEM), the possible surface localization of some H. pylori antigens that may be important virulence factors. All four methods detected the lipopolysaccharide and the N -acetyl-neuroaminyllactose-binding hemagglutinin protein (HpaA) as surface-exposed, while the urease enzyme was not detected at all and the neutrophil activating protein only in low concentration on the surface of the H. pylori bacteria during culture of H. pylori in liquid broth for 11 days. The FCM analysis was found to be quite sensitive and specific and also extremely fast compared with IF and IEM, and therefore the preferred method for detection of surface-localized antigens of H. pylori. [source] Purification and characterization of a glutathione S -transferase from the fungus Cunninghamella elegansFEMS MICROBIOLOGY LETTERS, Issue 2 2001Chang-Jun Cha Abstract Cunninghamella elegans grown on Sabouraud dextrose broth had glutathione S -transferase (GST) activity. The enzyme was purified 172-fold from the cytosolic fraction (120,000×g) of the extract from a culture of C. elegans, using Q-Sepharose ion exchange chromatography and glutathione affinity chromatography. The GST showed activity against 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene, 4-nitrobenzyl chloride, and ethacrynic acid. Sodium dodecyl sulfate,polyacrylamide gel electrophoresis gel filtration chromatography revealed that the native enzyme was homodimeric with a subunit of Mr 27,000. Comparison by Western blot analysis implied that this fungal GST had no relationship with mammalian ,-, ,-, and ,-class GSTs, although it showed a small degree of cross-reactivity with a ,-class GST. The N-terminal amino acid sequence of the purified enzyme showed no significant homology with other known GSTs. [source] Regulation of whole bacterial pathogen transcription within infected hostsFEMS MICROBIOLOGY REVIEWS, Issue 3 2008My-Van La Abstract DNA microarrays are a powerful and promising approach to gain a detailed understanding of the bacterial response and the molecular cross-talk that can occur as a consequence of host,pathogen interactions. However, published studies mainly describe the host response to infection. Analysis of bacterial gene regulation in the course of infection has confronted many challenges. This review summarizes the different strategies used over the last few years to investigate, at the genomic scale, and using microarrays, the alterations in the bacterial transcriptome in response to interactions with host cells. Thirty-seven studies involving 19 different bacterial pathogens were compiled and analyzed. Our in silico comparison of the transcription profiles of bacteria grown in broth or in contact with eukaryotic cells revealed some features commonly observed when bacteria interact with host cells, including stringent response and cell surface remodeling. [source] Starch-like exopolysaccharide produced by the filamentous fungi Ophiostoma ulmi and O. novo-ulmiFOREST PATHOLOGY, Issue 2 2007R. Jeng Summary This paper describes the chemical and biochemical properties of exopolysaccharides (EPS) produced by Ophiostoma ulmi and O. novo-ulmi isolates, the Dutch elm disease (DED) fungi. Some of EPS have been considered as pathogenicity factor in the DED complex. The selected isolates grow well and produce EPS in a medium containing various types of carbon and nitrogen sources. EPS obtained from potato dextrose broth (PDB) medium appeared to be opaque, firm and stained purple blue with iodine-potassium iodide solution, whereas those from yeast extract (YE) medium were less opaque, jelly-like and remained unchanged in iodine solution. The selected fungal isolates produced much higher molecular weight EPS from the medium containing YE than from PDB. The results of this study suggest that high molecular weight compounds produced by O. ulmi (W9) and O. novo-ulmi (R136) are not involved in DED pathogenesis. Spectrometric analysis of acid-digested EPS obtained from PDB and YE revealed the presence of a monomer similar to glucose used as a standard. Thin layer chromatography indicated that glucan-1,4- , -glucosidase (glucoamylase) only hydrolyses EPS from PDB media and releases glucose. The results strongly indicate that isolates of O. ulmi and O. novo-ulmi produce starch-like EPS from PDB medium. The EPS obtained from YE medium lacked this characteristic. The biological significance and the potential use of these EPS are discussed. [source] Methodology and Transport Medium for Collection of Helicobacter pylori on a String Test in Remote LocationsHELICOBACTER, Issue 6 2005Helen M. Windsor ABSTRACT Background.,Helicobacter pylori can be isolated from patients using the string test but contaminating oral and nasopharyngeal microflora need to be suppressed by rapid plating out onto selective culture media. Recently, use of this diagnostic method was enhanced by using a novel transport medium to collect specimens from subjects in a remote Australian clinic over 1300 km from the laboratory. Methods., Retrieved string tests were transported to the laboratory in chilled polystyrene boxes in 5 ml screw-cap bottles with 3 ml of a brain heart infusion broth plus antibiotics. These were 20 g/ml vancomycin, 10 g/ml trimethoprim, 10 g/ml cefsulodin, and 10 g/ml amphotericin B. A comparison was made between subjects who gargled with a chlorhexidine mouthwash before swallowing the string test and those who did not. Results., Forty-five urea breath test-positive subjects were tested and H. pylori was isolated from 34 of them. Successful culture was achieved from string tests that were in transit for up to 29 hours and where the maximum temperature in the transport box was 14 °C. The additional use of a mouthwash had a marked effect on the isolation rate. H. pylori was cultured from 75% of subjects who gargled but only from 39% who did not. Conclusions., This methodology and transport medium can broaden the use of the string test to more remote geographic areas where endoscopy is not feasible so that H. pylori isolates may still be obtained for diagnostic and epidemiologic studies. The value of this promising methodology of collection and transport should be assessed in a controlled study. [source] A laboratory assessment of coronal bacterial leakage in root canals filled with new and conventional sealersINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2009A. U. Eldeniz Abstract Aim, To evaluate the resistance to ex vivo bacterial leakage over a 40-day period of root canal fillings with five new root canal sealers: RC Sealer, Epiphany, EndoREZ, GuttaFlow and Acroseal, compared with Apexit, AH Plus and RoekoSeal. Methodology, One hundred and forty-four single rooted human teeth were divided randomly into eight test (n = 15) and two control groups (n = 12). The root canals were filled using a single cone technique with gutta-percha except in the Epiphany and EndoREZ groups. These were filled with Resilon and resin-coated gutta-percha, respectively. The gutta-percha surface of the GuttaFlow group was coated with an experimental primer prior to filling. Positive controls were filled with gutta-percha without sealer and tested with bacteria, whereas negative controls were sealed with wax to test the seal between the chambers. Filled roots were incorporated in a split chamber model system using Streptococcus mutans as a microbial marker. Leakage was assessed for turbidity of the broth in the lower chamber every day for 40 days. Survival analysis was performed using the Kaplan,Meier product limit method and event times were compared using the Log-rank test (, = 0.05). Results, Epiphany, GuttaFlow with test primer and Apexit prevented leakage significantly better than AH Plus, RC Sealer, RoekoSeal, EndoREZ and Acroseal (P < 0.05). None of the specimens in the AH Plus, RC Sealer, RoekoSeal and EndoREZ groups resisted bacterial penetration for 40 days. Conclusion, The new sealers, Epiphany and GuttaFlow with primer, along with Apexit, showed better resistance to bacterial penetration than the other new or traditional sealers tested. [source] Efficacy of various concentrations of NaOCl and instrumentation techniques in reducing Enterococcus faecalis within root canals and dentinal tubulesINTERNATIONAL ENDODONTIC JOURNAL, Issue 1 2006V. B. Berber Abstract Aim, To evaluate the efficacy of 0.5%, 2.5% and 5.25% sodium hypochlorite (NaOCl) as intracanal irrigants associated with hand and rotary instrumentation techniques against Enterococcus faecalis within root canals and dentinal tubules. Methodology, A total of 180 extracted human premolar teeth were infected for 21 days with E. faecalis. The specimens were divided into 12 groups, as follows: group 1: 5.25% NaOCl + Hybrid technique (Valdrighi et al. 1998); group 2: 5.25% NaOCl + nickel,titanium (NiTi) rotary technique 4 mm shorter than the apex (by FOP-UNICAMP); group 3: 5, 25% NaOCl + NiTi rotary technique (Hero 642); group 4: 2.5% NaOCl +Hybrid technique; group 5: 2.5% NaOCl + NiTi rotary technique 4 mm shorter than the apex; group 6: 2.5% NaOCl + NiTi rotary technique (Hero 642); group 7: 0.5% NaOCl + Hybrid technique; group 8: 0.5% NaOCl + NiTi rotary technique 4 mm shorter than the apex; group 9: 0.5% NaOCl + NiTi rotary technique (Hero 642); group 10: sterile saline solution + Hybrid technique; group 11: sterile saline solution + NiTi rotary technique 4 mm shorter than the apex; group 12: sterile saline solution + NiTi rotary technique (Hero 642). Canals were sampled before and after preparation. After serial dilution, samples were plated onto brain heart infusion (BHI) agar, and the colony forming units (CFU) that were grown were counted. The teeth were sectioned into three thirds and dentine chips were removed from the canals with conical burs. The samples obtained with each bur were immediately collected into test tubes containing BHI broth, and were incubated at 37 °C and plated onto BHI agar. The CFU were counted and analysed. Results, At all depths and thirds of the root canals and for all techniques used, 5.25% NaOCl was shown to be the most effective irrigant solution tested when dentinal tubules were analysed, followed by 2.5% NaOCl. No differences among concentrations in cleaning the canals were found. Conclusions, Especially at higher concentrations, NaOCl, was able to disinfect the dentinal tubules, independent of the canal preparation technique used. [source] Recovery of Enterococcus faecalis after single- or multiple-visit root canal treatments carried out in infected teeth ex vivoINTERNATIONAL ENDODONTIC JOURNAL, Issue 10 2005N. Vivacqua-Gomes Abstract Aim, To assess the presence of Enterococcus faecalis after root canal treatment in single or multiple visits in an ex vivo model. Methodology, Forty-five premolar teeth were infected ex vivo with E. faecalis for 60 days. The canals were then prepared using a crowndown technique with System GT and Gates,Glidden burs and irrigated with 2% chlorhexidine gel. The specimens were divided into five groups (G1, G2, G3, G4 and G5) according to the time elapsed between chemical,mechanical preparation and root canal filling, the irrigant solution used and the use or nonuse of a calcium hydroxide intra-canal medicament. The teeth were then root-filled and incubated for 60 days at 37 °C. Dentine chips were removed from the canal walls with sequential sterile round burs at low speed. The samples obtained with each bur were immediately collected in separate test tubes containing Brain,Heart Infusion broth. These samples were placed onto agar plates and colony forming units were counted after 24 h at 37 °C. Data were ranked and analysed using the Kruskal,Wallis statistical test. Results,Enterococcus faecalis was recovered from 20% (three of 15 specimens) of G1 (chlorhexidine irrigation and immediate root filling in a single visit), 25% (four of 15 specimens) of G2 (chlorhexidine irrigation and filling after 14 days use of a calcium hydroxide dressing in multiple visits), 40% (two of five specimens) of G3 (chlorhexidine irrigation and filling after 7 days), 60% (three of five specimens) of G4 (saline irrigation and filling after 7 days) and from 100% (five of five specimens) of G5 (saline irrigation and immediate filling without sealer). Conclusions, Neither single- nor multiple-visit root canal treatment ex vivo, eliminated E. faecalis completely from dentinal tubules. Up to 60 days after root filling, E. faecalis remained viable inside dentinal tubules. When no sealer was used, E. faecalis presented a higher growth rate. [source] An in-vitro investigation of the antibacterial effect of nisin in root canals and canal wall radicular dentineINTERNATIONAL ENDODONTIC JOURNAL, Issue 10 2004S. R. Turner Abstract Aim, To determine whether nisin, a bacteriocin, would be effective at killing Enterococcus faecalis and Streptococcus gordonii cells in solution and within the root canal system. Methodology, Bacterial isolates of E. faecalis and S. gordonii were grown from glycerol stocks in closed tubes containing BHY broth at 37 °C. The minimum bactericidal concentration (MBC) of nisin for both bacterial species was determined by a microdilution method. Extracted human teeth were decoronated to produce roots of equal length with a single canal and divided into six groups of 10 roots. The canals were prepared to a master apical size 30 file using 0.04 taper Ni-Ti rotary instruments. Bacterial samples of each species were inoculated into three groups of prepared roots and incubated in closed tubes at 37 °C for 21 days. The root canals in each group were then medicated with water (control), calcium hydroxide powder mixed with sterile water [Ca(OH)2], or nisin and incubated for a further 7 days. Rotary Ni-Ti files were used to take radicular dentine samples from the walls of each canal which were then incubated in BHY broth for 24 h. Optical density (OD600) readings were taken as a measure of bacterial growth. Results, The MBC of nisin for E. faecalis and S. gordonii was 70 and 20 mg mL,1 respectively. Calcium hydroxide and nisin medication eradicated infection within the root canal while cells remained viable in the control group. Mean optical density (OD600) readings from canal wall dentine shavings infected with E. faecalis were 1.32 ± 0.98, 0.73 ± 0.27 and 0.69 ± 0.38 for the control, Ca(OH)2 and nisin samples respectively. Corresponding mean readings for S. gordonii were 1.19 ± 0.18, 0.73 ± 0.15 and 0.60 ± 0.29. The Ca(OH)2 and nisin group readings were significantly (P < 0.01) lower than the control for each species as tested by Student's t -test and Mann,Whitney U statistical analysis. Values for Ca(OH)2 and nisin were not significantly (P > 0.01) different. Conclusion, Nisin was effective at eradicating E. faecalis and S. gordonii cells in pure culture and was comparable with Ca(OH)2 in the elimination of these species from within the root canal system. [source] Effect of conditioning films and a novel anti-adherent agent on bacterial adherence to dentineINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2001A. Maglad Aim,Adherence of bacteria to dentine is a prerequisite to infection of the root canal system, yet adherence of root canal bacteria to dentine is poorly understood. The aim of this study was to evaluate the effect of conditioning films and anti-adherent compounds on bacterial adherence to dentine. Methodology,Freshly extracted molar teeth were prepared and sectioned to give 225 discs of predetermined dimensions. The discs were allocated to two groups. Group 1 (n = 189) was divided into three subgroups (n = 63) and coated with one of three conditioning agents (artificial saliva, serum, or distilled water) prior to bacterial inoculation. Group 2 discs (n = 36) were treated with either a novel anti-adherent agent (PC1036, Biocompatibles) (n = 18) or distilled water (n = 18) prior to conditioning with artificial saliva. Monospecies bacterial biofilms were generated on the dentine discs by incubating them in brain heart infusion broth (37 gL,1) containing Streptococcus intermedius (Si), Enterococcus faecalis (Ef) or Lactobacillus fermentum (Lf) (originally isolated from infected root canals). The number of bacteria adhering to the discs in each of the groups was determined using standard serial dilution protocols. Additional discs were prepared under all conditions for scanning electron microscopy. Where appropriate, statistical analysis by one way anova, post hoc Bonferroni, and independent t -test were used. Results,Si adhered significantly better to dentine when conditioned with serum compared with artificial saliva (P = 0.005) or distilled water (P = 0.009). Conversely, Ef adhered significantly better to the control discs (distilled water) compared with serum conditioned discs (P = 0.016). The conditioning films had no effect on the adherence of Lf, which adhered to the dentine discs significantly less (P = 0.001) than either Si or Ef. The anti-adherent coating significantly reduced the number of Si adhering to the dentine compared with the control (P = 0.012). Conclusion,Given the importance of adherence in root canal infection it is conceivable that an anti-adherent compound, could be used to prevent bacterial recontamination of cavities or the root canal system. [source] Antimicrobial activity of nisin incorporated in pectin and polylactic acid composite films against Listeria monocytogenesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2009Tony Jin Summary An extruded composite food packaging film containing pectin, polylactic acids (PLAs) and nisin was developed to inhibit Listeria monocytogenes. The mechanical properties and surface structure of the film were also examined. Cells of L. monocytogenes were reduced by 2.1, 4.5 and 3.7 log units mL,1 by the pectin plus PLA (pectin/PLA) film containing nisin (1000 IU mL,1 of tested liquid) in Brain Heart Infusion (BHI) broth, liquid egg white and orange juice, respectively, after 48 h at 24 °C. Pectin played an important roll in embedding nisin into the film. The pectin/PLA film had a similar stiffness but lower tensile strength, elongation and fracture energy than the pure PLA film. These data suggested that nisin incorporated into the pectin/PLA film was an effective approach to reducing L. monocytogenes in a typical growth medium (e.g. BHI broth) as well as in foods (e.g. orange juice and liquid egg). [source] Quantifying the heterogeneous heat response of Escherichia coli under dynamic temperaturesJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2010E. Van Derlinden Abstract Aims:, Non-sigmoid growth curves of Escherichia coli obtained at constant temperatures near the maximum growth temperature (Tmax) were previously explained by the coexistence of two subpopulations, i.e. a stress-sensitive and a stress-resistant subpopulation. Mathematical simulations with a heterogeneous model support this hypothesis for static experiments at 45°C. In this article, the behaviour of E. coli, when subjected to a linearly increasing temperature crossing Tmax, is studied. Methods and Results:, Subpopulation dynamics are studied by culturing E. coli K12 MG1655 in brain heart infusion broth in a bioreactor. The slowly increasing temperature (°C h,1) starting from 42°C results in growth up to 60°C, a temperature significantly higher than the known Tmax. Given some additional presumptions, mathematical simulations with the heterogeneous model can describe the dynamic experiments rather well. Conclusions:, This study further confirms the existence of a stress-resistant subpopulation and reveals the unexpected growth of E. coli at temperatures significantly higher than Tmax. Significance and Impact of the Study:, The growth of the small stress-resistant subpopulation at unexpectedly high temperatures asks for a revision of currently applied models in food safety and food quality strategies. [source] Effects of thymol and diphenyliodonium chloride against Campylobacter spp. during pure and mixed culture in vitroJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2009R.C. Anderson Abstract Aims:, To determine if the purported deaminase inhibitors diphenyliodonium chloride (DIC) and thymol reduce the growth and survivability of Campylobacter. Methods and Results:, Growth rates of Campylobacter jejuni and Camp. coli were reduced compared to unsupplemented controls during culture in Muellar,Hinton broth supplemented with 0·25 ,mol DIC or thymol ml,1 but not with 0·01 ,mol monensin ml,1 or 1% ethanol. Recovery of Camp. jejuni and Camp. coli was reduced >5 log10 CFU from controls after 24 h pure culture in Bolton broth supplemented with 0·25 or 1·0 ,mol DIC ml,1 or with 1·0 ,mol thymol ml,1. Similarly, each test Campylobacter strain was reduced >3 log10 CFU from controls after 24 h mixed culture with porcine faecal microbes in Bolton broth supplemented with 0·25 or 1·0 ,mol DIC ml,1 or with 1·0 ,mol thymol ml,1. Treatments with 0·25 ,mol thymol ml,1, 0·01 ,mol monensin ml,1 or 1% ethanol were less effective. Ammonia production during culture or incubation of cell lysates was reduced by 0·25 or 1·0 ,mol DIC ml,1 but only intermittently reduced, if at all, by the other treatments. Conclusions:, Diphenyliodonium chloride and thymol reduced growth, survivability and ammonia production of Camp. jejuni and Camp. coli. Significance and Impact of the Study:, Results suggest a potential physiological characteristic that may be exploited to develop interventions. [source] Kinetics of microbial hydrogenation of free linoleic acid to conjugated linoleic acidsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008H. Xu Abstract Aims:, To investigate the ability of selected probiotic bacterial strains to produce conjugated linoleic acid (CLA) and also to estimate the biohydrogenation kinetics of Lactobacillus acidophilus on the production of CLA from free linoleic acid (LA). Methods and Results:, Six probiotic bacteria, Lact. paracasei, Lact. rhamnosus GG, Lact. acidophilus ADH, and Bifidobacterium longum B6, Lact. brevis, and Lact. casei, were used to examine their ability to convert LA to CLA. LA tolerance was evaluated by addition of different LA concentrations in MRS broth. Lact. acidophilus showed the major tolerant to LA and the greatest CLA-producing ability (36,48 ,g ml,1 of CLA). The rate-controlling steps were k2 and k1 for the addition of 1 and 3 mg ml,1 of LA, respectively. The percentage of CLA conversion was higher in MRS broth supplemented with 1 mg ml,1 (65%) than 3 mg ml,1 (26%). Conclusion:, The results provide useful information and new approach for understanding the biohydrogenation mechanisms of CLA production. Significance and Impact of the Study:, This study would help elucidate the pathway from LA to stearic acid (SA), known as biohydrogenation. In addition, the use of selected probiotic bacteria might lead to a significant improvement in food safety. [source] The growth limits of a large number of Listeria monocytogenes strains at combinations of stresses show serotype- and niche-specific traitsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2008S. Van Der Veen Abstract Aims:, The aim of this study was to associate the growth limits of Listeria monocytogenes during exposure to combined stresses with specific serotypes or origins of isolation, and identify potential genetic markers. Methods and Results:, The growth of 138 strains was assessed at different temperatures using combinations of low pH, sodium lactate, and high salt concentrations in brain heart infusion broth. None of the strains was able to grow at pH , 4·4, aw , 0·92, or pH , 5·0 combined with aw , 0·94. In addition, none of the strains grew at pH , 5·2 and NaLac , 2%. At 30°C, the serotype 4b strains showed the highest tolerance to low pH and high NaCl concentrations at both pH neutral (pH 7·4) and mild acidic conditions (pH 5·5). At 7°C, the serotype 1/2b strains showed the highest tolerance to high NaCl concentrations at both pH 7·4 and 5·5. Serotype 1/2b meat isolates showed the highest tolerance to low pH in the presence of 2% sodium lactate at 7°C. ORF2110 and gadD1T1 were identified as potential biomarkers for phenotypic differences. Conclusions:, Differences in growth limits were identified between specific L. monocytogenes strains and serotypes, which could in some cases be associated with specific genetic markers. Significance and Impact of the Study:, Our data confirm the growth limits of L. monocytogenes as set out by the European Union for ready-to-eat foods and provides an additional criterion. The association of L. monocytogenes serotypes with certain stress responses might explain the abundance of certain serotypes in retail foods while others are common in clinical cases. [source] Isolation and partial characterization of a bacteriocin produced by Pediococcus pentosaceus K23-2 isolated from KimchiJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2008M.S. Shin Abstract Aims:, Screening and partial characterization of a bacteriocin produced by Pediococcus pentosaceus K23-2 isolated from Kimchi, a traditional Korean fermented vegetable. Methods and Results:, A total of 1000 lactic acid bacteria were isolated from various Kimchi samples and screened for the production of bacteriocin. Pediocin K23-2, a bacteriocin produced by the Pediococcus pentosaceus K23-2 strain, showed strong inhibitory activity against Listeria monocytogenes. The bacteriocin activity remained unchanged after 15 min of heat treatment at 121°C or exposure to organic solvents; however, it diminished after treatment with proteolytic enzymes. The bacteriocin was maximally produced at 37°C, when the pH of the culture broth was maintained at 5·0 during the fermentation, although the optimum pH for growth was 7·0. The molecular weight of the bacteriocin was about 5 kDa according to a tricine SDS-PAGE analysis. Conclusions:,Pediococcus pentosaceus K23-2 isolated from Kimchi produces a bacteriocin, which shares similar characteristics to the Class IIa bacteriocins. The bacteriocin is heat stable and shows wide antimicrobial activity against Gram-positive bacteria, especially L. monocytogenes. Significance and Impact of the Study:, Pediocin K23-2 and pediocin K23-2-producing P. pentosaceus K23-2 could potentially be used in the food and feed industries as natural biopreservatives, and for probiotic application to humans or livestock. [source] Response of Listeria monocytogenes to liquid smokeJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008M. Guilbaud Abstract Aims:, To investigate the effect of liquid smoke on growth, survival, proteomic pattern and haemolytic potential of Listeria monocytogenes. Methods and Results:, Growth and survival curves were recorded in brain,heart infusion broth supplemented with three concentrations of liquid smoke. L. monocytogenes growth was inhibited in the presence of 15 ,g ml,1 phenol while a rapid decrease in cell viability occurred in the presence of 30 ,g ml,1 phenol. The proteome of L. monocytogenes cytosoluble proteins was slightly modified after 2-h incubation with 30 ,g ml,1 phenol but no protein already characterized in response to other known stresses was induced, except the protease ClpP. Liquid smoke inhibited the haemolytic potential without affecting hly gene expression, showing a potential inhibition of protein activity or stability. Conclusions:, The presence of liquid smoke in a rich medium strongly affected growth and survival of L. monocytogenes. Brief smoke stress affected the metabolic pathways and inhibited the haemolytic activity of L. monocytogenes. Significance and Impact of Study:, This study is a first step in the investigation of the influence of a smoked product on L. monocytogenes strains. [source] Antioxidant polyphenols from the mycelial culture of the medicinal fungi Inonotus xeranticus and Phellinus linteusJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008J.-Y. Jung Abstract Aims:, The medicinal fungi Inonotus xeranticus and Phellinus linteus in the family Hymenochaetaceae have been used as traditional medicines for the treatment of various diseases. However, the compound responsible for the antioxidant activity is still unknown. Therefore, this study was conducted to characterize the antioxidant substances present in cultured broths made from these fungi. Methods and Results:, Antioxidant fractions of the cultured broths obtained from I. xeranticus and P. linteus were analysed using reversed-phase HPLC, which revealed several peaks that exhibited a potent free radical scavenging activity. To identify these antioxidant peaks, an I. xeranticus strain was mass-cultured, and the cultured broth was separated using antioxidant activity-guided fractionation. Four major active substances were purified and identified as hispidin and its dimers, 3,14,-bihispidinyl, hypholomine B, and 1,1-distyrylpyrylethan based on spectroscopic analyses. All compounds exhibited a significant scavenging activity against these radical species in a concentration-dependent manner. Conclusions:, Antioxidant substances found in the cultured broths of the medicinal fungi I. xeranticus and P. linteus were identified as hispidin and its dimers, 3,14,-bihispidinyl, hypholomine B, and 1,1-distyrylpyrylethan. Significance and Impact of the Study:, Polyphenol antioxidants were isolated from the cultured broth of the medicinal fungi I. xeranticus and P. linteus and identified based on extensive spectroscopic analyses. These compounds exhibited a strong antioxidant activity. [source] Effects of porcine bile on survival of Bacillus cereus vegetative cells and Haemolysin BL enterotoxin production in reconstituted human small intestine mediaJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2007T. Clavel Abstract Aims: To determine the effects of porcine bile (PB) on Bacillus cereus vegetative cells and Haemolysin BL (HBL) enterotoxin production in reconstituted small intestine media (IM). Methods and Results: The effects of PB on the growth of B. cereus vegetative cells in reconstituted IM at PB concentrations ranging between 0 and 3·0 g l,1 were examined. Four gastric media (GM) named GM-J broth (JB), GM-chicken, GM-milk and GM-pea were prepared by mixing equal volumes of a gastric electrolyte solution containing pepsin with JB, chicken, semi-skimmed milk and pea soup, respectively. Bacillus cereus was inoculated at approx. 2 × 104 CFU ml,1 into each GM at pH 5·0 for 30 min at 37°C, then mixed to the same volume of double-strength JB (IM) and PB to give concentrations of between 0 and 3·0 g of PB per litre at pH 6·5 and incubated at 37°C. The diarrhoeal B. cereus strain F4430/73 grew in IM-JB, IM-chicken and IM-milk at PB concentrations of up to 0·6, 1·5 and 1·2 g l,1, respectively. Growth was observed in IM-pea at all concentrations tested. The highest PB concentrations allowing a 3 log B. cereus increase in IM-JB, IM-chicken, IM-milk and IM-pea after a 7,10 h incubation period were 0·3, 0·9, 0·9 and 3·0 g l,1, respectively. The effect of PB on B. cereus cells was strongest in IM-JB, followed by IM-chicken, IM-milk and IM-pea. Haemolysin BL enterotoxin was detectable in IM-chicken, IM-whole milk, IM-semi-skimmed milk and IM-pea up to PB concentrations of only 0·6, 0·6, 0·3 and 0·9 g l,1, respectively. The diarrhoeal B. cereus strain F4433/73 behaved similarly to B. cereus strain F4430/73, whereas the food strain TZ415 was markedly more susceptible to bile. Conclusions: The tolerance of B. cereus cells to PB strongly depends on the type of food contained in the IM. Bile tolerance is also subject to strain variation. Significance and Impact of the Study: The probability that B. cereus cells will grow in the small intestine, produce toxins and cause diarrhoea is likely to depend on the food they are ingested with, on the bile tolerance of the B. cereus strain, and on bile concentration. [source] Evaluation of novel fluorogenic substrates for the detection of glycosidases in Escherichia coli and enterococciJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2006J.D. Perry Abstract Aims:, Enzyme substrates based on 4-methylumbelliferone are widely used for the detection of Escherichia coli and enterococci in water, by detection of , -glucuronidase and , -glucosidase activity respectively. This study aimed to synthesize and evaluate novel umbelliferone-based substrates with improved sensitivity for these two enzymes. Methods and Results:, A novel , -glucuronide derivative based on 6-chloro-4-methylumbelliferone (CMUG) was synthesized and compared with 4-methylumbelliferyl- , - d -glucuronide (MUG) using 42 strains of E. coli in a modified membrane lauryl sulfate broth. Over 7 h of incubation, the fluorescence generated from the hydrolysis of CMUG by E. coli was over twice that from MUG, and all of the 38 glucuronidase-positive strains generated a higher fluorescence with CMUG compared with MUG. Neither substrate caused inhibition of bacterial growth in any of the tested strains. Four , -glucosidase substrates were also synthesized and evaluated in comparison with 4-methylumbelliferyl- , - d -glucoside (MU-GLU) using 42 strains of enterococci in glucose azide broth. The four substrates comprised , -glucoside derivatives of umbelliferone-3-carboxylic acid and its methyl, ethyl and benzyl esters. Glucosides of the methyl, ethyl and benzyl esters of umbelliferone-3-carboxylic acid, were found to be superior to MU-GLU for the detection of enterococci, especially after 18 h of incubation, while umbelliferone-3-carboxylic acid- , - d -glucoside was inferior. However, the variability in detectable , -glucosidase activity among the different strains of enterococci in short-term assays using the three carboxylate esters (7 h incubation) may compromise their use for rapid detection and enumeration of these faecal indicator bacteria. Conclusions:, The , -glucuronidase substrate CMUG appears to be a more promising detection system than the various , -glucosidase substrates tested. Significance and Impact of the Study:, The novel substrate CMUG showed enhanced sensitivity for the detection of , -glucuronidase-producing bacteria such as E. coli, with a clear potential for application in rapid assays for the detection of this indicator organism in natural water and other environmental samples. [source] Physicochemical properties of Shiga toxigenic Escherichia coliJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2005L. Rivas Abstract Aims:, To investigate the physicochemical surface properties, such as cellular surface charge, hydrophobicity and electron donor/acceptor potential of a selection of Shiga toxigenic Escherichia coli (STEC) isolates grown in broth and agar culture. Methods and Results:, Cellular surface charge was determined using zeta potential measurements. Hydrophobicity of the isolates was determined using bacterial adhesion to hydrocarbons assay, hydrophobic interaction chromatography and contact angle measurements. Microbial adhesion to solvents was used to determine the electron donor/acceptor characteristics. No differences of surface charge measurements were found between broth and agar grown cultures. Isolates belonging to serogroup O157 and serotypes O26:H11 and O111:H- were significantly (P < 0·05) less negatively charged than other STEC serotypes tested. All strains were hydrophilic with most methods and demonstrated a lower hydrophobicity in agar culture compared with broth culture. All strains demonstrated a strong microbial adhesion to chloroform indicating that STEC possess an electron donor and basic character. A relationship between serogroup O157 and other STEC serotypes was apparent using principal-component analysis (PCA). Conclusions:, Combining the results for physicochemical properties using PCA differentiated between strains belonging to the O157 serogroup and other STEC/non-STEC strains. PCA found similar results for broth and agar grown cultures. Significance and Impact of the Study:, Particular serotypes of STEC possess similar physicochemical properties which may play a role in their pathogenicity or potential attachment to various surfaces. [source] Rapid and effective detection of anthrax spores in soil by PCRJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2003H.I. Cheun Abstract Aims: To detect Bacillus anthracis DNA from soil using rapid and simple procedures. Methods and Results: Various amounts of B. anthracis Pasteur II spores were added artificially to 1 g of soil, which was then washed with ethanol and sterile water. Enrichment of the samples in trypticase soy broth was performed twice. A DNA template was prepared from the second enrichment culture using a FastPrep instrument. The template was then used for nested and real-time polymerase chain reaction (PCR) with B. anthracis -specific primers, to confirm the presence of B. anthracis chromosomal DNA and the pXO1/pXO2 plasmids. Conclusions: One cell of B. anthracis in 1 g of soil could be detected by nested and real-time PCR. The usefulness of the PCR method using field samples was also confirmed. Significance and Impact of the Study: The results indicate that this could be a useful method for detecting anthrax-spore contaminated soil with high sensitivity. Its application could have great impact on the progress of epidemiological surveillance. [source] | ||||||||||||||||||||||||||||||||||