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Viable Counts (viable + count)
Kinds of Viable Counts Selected AbstractsSurvival and gene expression of enterotoxigenic Escherichia coli during long-term incubation in sea water and freshwaterJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2010Å. Lothigius Abstract Aims:, In this study, the main objective was to verify the hypothesis of induction of ,viable but non-culturable' (VBNC) forms of enterotoxigenic Escherichia coli (ETEC) during incubation in water. Methods and Results:, Six clinically isolated ETEC strains were studied. Viable counts showed culturable ETEC bacteria for up to 3 months in freshwater but only two out of six strains were culturable in seawater at this time point. Although the bacterial cells remained intact, no production or secretion of heat-labile (LT) or heat-stable (ST) enterotoxins was observed using GM1-ELISA methods. However, genes encoding ETEC toxins (STh and LT), colonization factors (CS7 and CS17), gapA and 16S RNA were expressed during 3 months in both sea water and freshwater microcosms as determined by real-time RT-PCR on cDNA derived from the bacteria. Conclusions:, Clinically isolated ETEC strains can survive for long periods in both sea water and freshwater. The bacterial cells remain intact, and the gene expression of virulence genes and genes involved in metabolic pathways are detected after 3 months. Significance and Impact of the Study:, These results indicate that ETEC bacteria can enter a VBNC state during stressful conditions and suggest that ETEC has the potential to be infectious after long-term incubation in water. [source] Bacteriological quality of skin-moisturizing creams and lotions distributed in a tropical developing countryJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2001I.N. Okeke Aims: To evaluate the bacteriological quality of skin moisturizing products in the South-west part of Nigeria and study factors predisposing their bacterial contamination under tropical conditions. Methods and Results: Viable counts for bacteria exceeded 103 cfu ml,1or cfu g,1 in 8 (16·3%) commercially available creams and lotions at time of purchase. Escherichia coli (8), Pseudomonas spp. (7), Staphylococcus spp. (9) and Bacillus spp. (6) were the most commonly recovered bacteria. Following use by volunteers, the proportion of E. coli and other Gram-negative organisms recovered increased. Organic matter, particularly in the absence of preservatives, enhanced survival and growth of bacteria in creams stored under ambient tropical conditions during challenge experiments. Conclusions: Contaminated products are relatively uncommon but some products present a potential health hazard because they are unable to suppress the growth of organisms of likely faecal origin during use. Significance and Impact of the Study: Quality assurance during manufacture, pack size, preservative evaluation, organic matter and water content were identified as factors to be considered during the development of creams and lotions for use in tropical developing countries. [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] Microbial community diversity associated with the intestinal mucosa of farmed rainbow trout (Oncoryhnchus mykiss Walbaum)AQUACULTURE RESEARCH, Issue 9 2009Daniel L Merrifield Abstract Bacterial communities from the intestinal tract of rainbow trout were investigated to assess transient and resident microbial communities using both culture-based and culture-independent techniques. Viable counts attached to the intestinal mucosa were in the range of log 4.77,5.38 and log 6.67,6.79 CFU g,1 in the intestinal contents. Pseudomonas spp. and Enterobacteriaceae constituted nearly 80% of the allochthonous population but <60% of the autochthonous populations. This coincided with an elevated mucosal level of a group of Gram-positive rods from ,2% in the digesta to 25,35% on the mucosa. This group was identified by 16S rRNA as Arthrobacter aurescens and Janibacter spp. HTCC2649. Analysis of denaturing gradient gel electrophoresis banding patterns showed complex communities in all intestinal regions. Similarity coefficients showed that mucosal communities were ,70% similar to digesta communities and yet due to the presence of bands found uniquely either in the digesta or on the mucosa, the communities are distinctly different. Scanning electron microscopy confirmed mucosal bacterial populations and highlighted a possible localized colonization between mucosal folds. The study highlights the complexity of resident microbial communities that have not been fully explored in previous rainbow trout studies; this is especially true with probiotic/prebiotic investigations. [source] The effects of ice storage on inosine monophosphate, inosine, hypoxanthine, and biogenic amine formation in European catfish (Silurus glanis) filletsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 10 2009Fatih Özogul Summary European catfish fillets in ice were evaluated by measuring nucleotide components and biogenic amine contents and these then compared with sensory and microbiological assessment during the 21 days of iced storage. Analyses were carried out using two different rapid HPLC methods for nucleotid degradation products and biogenic amine contents in European catfish fillets. Sensory evaluation showed that storage life of European catfish found to be 14,18 days. Initial inosine monophosphate (IMP) level was 12.6 ,mol g1 and then decreased during the rest of storage period. Inosine (INO) level increased rapidly until 7 days of storage. Hypoxanthine (Hx) level increased almost linearly with storage time. The most accumulated biogenic amines were putrescine, cadaverine, spermidine, spermine, and serotonin in all the European catfish fillets during the storage, although the formation of biogenic amines levels was fluctuated. Histamine was only detectable at 4 and 7 days of storage as low as 1 mg 100 g1 fish. Total viable count in European catfish increased rapidly with storage time and reached ,109 cfu g1 when the fillets were not acceptable for consumption. [source] Chemical composition and inhibitory effect of essential oil and organic extracts of Cestrum nocturnum L. on food-borne pathogensINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2009Sharif M. Al-Reza Summary In this study, we examined the chemical compositions of essential oil and tested the efficacy of oil and organic extracts of Cestrum nocturnum L. against food-borne pathogens. The chemical compositions of the oil was analysed by gas chromatography-mass spectrometry (GC-MS). Forty-seven compounds representing 93.28% of the total oil were identified. The oil [5 ,L of 1:5 (v/v) dilution of oil with methanol] and organic extracts of hexane, chloroform, ethyl acetate and methanol (300 ,g per disc) of C. nocturnum displayed a great potential of antibacterial activity against Staphylococcus aureus (ATCC 6538 and KCTC 1916), Listeria monocytogenes (ATCC 19166 and ATCC 15313), Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa KCTC 2004, Salmonella typhimurium KCTC 2515 and Escherichia coli ATCC 8739. Also the oil had strong detrimental effect on the viable count of the tested bacteria. The results obtained from this study may contribute to the development of new antimicrobial agents with potential applications in food industries as natural preservatives to control food-borne pathogens. [source] Suitability of bifidobacteria and thymol as biopreservatives in extending the shelf life of fresh packed plaice filletsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2005C. Altieri Abstract Aims:, The present study was aimed to evaluate the microbiological and sensory characteristics of biopreserved packed fresh plaice (Pleuronectes platessa), during storage. Methods and Results:, Fish samples were treated with a Bifidobacterium bifidum strain and thymol as preservatives, stored at different temperatures (4 and 12°C) and package atmospheres (in air, under vacuum, modified atmosphere). Data about the total viable count (TVC) were used to predict the shelf life of the fish fillets as affected by the preservatives used and the storage conditions. Data obtained revealed that B. bifidum could perform an efficient synergy with thymol, in controlling the hygiene biological markers. Besides, the tested bifidobacterial species, combined with low storage temperature and anoxia/hypoxia, showed a great efficacy against the main fresh packaged fish spoilage species (Pseudomonas spp., Photobacterium phosphoreum). Conclusions:, The studied technique could be considered effective in fresh fish spoilage control. Significance and Impact of the Study:, Great interest is developing on food biopreservation, because of the ever increasing needs to protect consumers' and environment's health, and to revalorize some important food characteristics, such as naturalness and authenticity, without leaving the safety aside. [source] STRATEGIES FOR PROLONGING THE SHELF LIFE OF MINCED BEEF PATTIESJOURNAL OF FOOD SAFETY, Issue 1 2009MATTEO ALESSANDRO DEL NOBILE ABSTRACT The study of different strategies for prolonging the shelf life of fresh minced beef patties was addressed in this work. Fresh minced beef was supplemented with thymol (THY) at levels of 250, 500 and 750 mg per kg of ground beef. Treated samples were packed using a high barrier film and stored in refrigerated conditions (4C) under ordinary atmosphere packaging and modified atmosphere packaging (MAP) conditions for 16 days. The microbiological quality decay kinetic was determined by monitoring the following microorganisms: Enterobacteriaceae, Pseudomonas spp., lactic acid bacteria, Brochothrix thermosphacta, coliforms and total psychrotrophic viable count. Results show that THY, working alone, was effective on coliforms and Enterobacteriaceae, whereas it does not seem to inhibit to a great extent the growth of the other microbial populations. On the other hand, an increased amount of THY, under MAP conditions, had better effects on the product quality, with a consequent prolongation of the shelf life. PRACTICAL APPLICATIONS Great interest is developing in food bio-preservation, because of the ever-increasing needs to protect consumers' health and to valorize the naturalness and safety of food products. However, very few works have been carried out on the applications of bio-preservatives to extend the shelf life of fresh meat products. This study, therefore, was mainly initiated to evaluate the possibility of extending the shelf life of packed fresh meat patties by a combination of thymol (THY) to other extrinsic factors such as storage temperatures and modified atmosphere during packaging. Interesting results were obtained suggesting that THY can perform an efficient synergy with modified atmosphere conditions and could be advantageously utilized by the meat industry. [source] Control of Plant Pathogenic Bacteria of Xanthomonas spp. by the Essential Oil and Extracts of Metasequoia glyptostroboides Miki ex Hu In vitro and In vivoJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2010Vivek K. Bajpai Abstract Plant diseases constitute an emerging threat to global food security. Many of the currently available antimicrobial agents for agriculture are highly toxic and non-biodegradable and cause extended environmental pollution. Therefore, this study was undertaken to assess the in vitro and in vivo antibacterial efficacy of the essential oil and organic extracts of Metasequoia glyptostroboides against plant pathogenic bacteria of Xanthomonas spp. The oil (1000 ,g/disc) and extracts (1500 ,g/disc) displayed potential antibacterial effect in vitro as a diameter of zones of inhibition against Xanthomonas campestris pv. campestris KC94-17-XCC, X. campestris pv. vesicatoria YK93-4-XCV, X. oryzae pv. oryzae KX019-XCO and X. sp SK12, which were found in the range of 10,14 and 8,12 mm, respectively. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of oil and the extracts were ranged from 125,250 and 125 500 ,g/ml and 250,1000 and 250,2000 ,g/ml, respectively. Also the oil had strong detrimental effect on the viable count of the tested bacteria. Further, the oil displayed remarkable in vivo antibacterial effect up to 65 to 100% disease suppression efficacy against the tested strains of Xanthomonas spp. on greenhouse-grown oriental melon plants (Cucumis melo L. var. makuwa). These results suggest that the oil and extracts of M. glyptostroboides could be potential source of natural antibacterials for applying in food and agriculture industries to control plant bacterial diseases caused by Xanthomonas spp. [source] Inactivation of Mycobacterium avium ssp. paratuberculosis in milk by UV treatmentLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2009J. Donaghy Abstract Aims:, To determine the effect of UV radiation on the viability of two strains of Mycobacterium avium ssp. paratuberculosis (Map) inoculated into milk. Methods and Results:,Mycobacterium avium ssp. paratuberculosis in a ultra heat treated milk matrix was subjected to increasing doses of UV-C radiation from 0 to 1836 mJ ml,1 using a pilot-scale UV reactor (20 l capacity). Survival of Map was monitored by culture on Herrold's egg yolk medium, Middlebrook 7H10 medium and the FASTPlaqueTBÔ phage assay. Differences in sensitivity to UV treatment were observed between strains, however, at 1000 mJ ml,1 a Map kill rate of 0·1,0·6 log10 was achieved regardless of strain used or method employed to enumerate Map. Although the inactivation trend was similar on the culture and phage assay, the former gave a consistently higher viable count. Conclusions:, The use of UV radiation alone does not represent an alternative to current pasteurization regimes for a large reduction in viable Map in milk. Significance and Impact of the Study:, To the authors' knowledge the work here represents the first pilot-scale UV treatment process used to assess UV efficacy to inactivate Map in milk. The results are similar to those obtained with a laboratory-scale process indicating the difficulties associated with UV treatment of an opaque liquid and the recalcitrance of Map towards inimical treatments. [source] Anticaries effect of compounds extracted from Galla Chinensis in a multispecies biofilm modelMOLECULAR ORAL MICROBIOLOGY, Issue 6 2008Q. Xie Introduction:,Galla Chinensis is a leaf gall known to have some antibacterial effects. Using an in vitro biofilm model of dental plaque, the present study aimed to evaluate the anticaries effects of Galla Chinensis and its chemical fractions. Methods:, A four-organism bacterial consortium (Streptococcus sanguis, Streptococcus mutans, Actinomyces naeslundii, Lactobacillus rhamnosus) was grown on hydroxyapatite (HA) discs, bovine enamel blocks, and glass surfaces in a continuous culture system and exposed to repeated solution pulses. Galla Chinensis extracts, sucrose solutions, and sodium fluoride solutions were pulsed into different flow cells. The pH value of the planktonic phase in each flow cell was recorded and the bacteria colonizing the biofilm on the HA discs were counted. Enamel blocks were observed using a polarized microscope and lesion depth was evaluated. The biofilm morphology was examined with a fluorescence microscope and the images captured were analyzed on an image analysis system. Results:, When Galla Chinensis extract, its chemical fraction, or fluoride was added to the sucrose solution, the planktonic phase pH remained higher than that in the sucrose alone. A lower level of colonization on the HA surface was also observed in the groups to which Galla Chinensis and fluoride were added compared with the control sucrose group, and this was reflected in both the total viable count and the biofilm imaging, which showed fewer cariogenic bacteria and a less compact biofilm, respectively. Enamel demineralization in both the fluoride group and the Galla Chinensis group was significantly less than that in the sucrose group. Conclusions:,Galla Chinensis and fluoride may inhibit the cariogenicity of the oral biofilm. Galla Chinensis appears to be a promising source of new agents that may prevent dental caries. [source] Effect of administration of acid- and bile-tolerant lactobacilli on pigs intestinal microbial populationANIMAL SCIENCE JOURNAL, Issue 6 2002Makoto OTSUKA ABSTRACT The effects of the administration of four Lactobacillus strains as probiotics on the constitution of microbial populations in the intestine of pigs were investigated by using a litter of pigs. The experimental group was fed a diet blended with the freeze-dried powder containing lactobacilli at a concentration of 0.2% (W/W). After 4 weeks of probiotics administration, the total viable count of anaerobes in the feces was not significantly different between the pigs fed a diet supplemented with probiotics and the pigs given the non-supplemented diet. However, viable counts of eubacteria were significantly higher (P < 0.01) in the feces of pigs fed a diet supplemented with probiotics than in the pigs given the non-supplemented diet. Conversely, viable counts of clostridia were significantly lower (P < 0.01) in the feces of pigs fed a diet supplemented with probiotics than the pigs given the non-supplemented diet. The total volatile fatty acid concentrations in the feces of pigs that were given a diet supplemented with probiotics were significantly lower (P < 0.05) than those given the non-supplemented diet. Further, the molar proportion of n-butyric acids in the feces of pigs that were given a diet supplemented with probiotics, was significantly lower (P < 0.05) than those given the non-supplemented diet. [source] Quality preservation of salted, vacuum packaged and refrigerated mahi sefid (Rutilus frisii kutum) fillets using an onion (Allium cepa) extractAQUACULTURE RESEARCH, Issue 8 2010Mehdi Zolfaghari Abstract The combined effect of light salting, vacuum packaging and onion extract on the shelf life of mahi sefid (Rutilus frisii kutum) fillets under refrigeration was assessed using chemical, microbiological and sensory methods. The shelf life of control, air-packaged, salted (APS), vacuum-packaged, salted (VPS) and vacuum-packaged, salted with onion extract (VPSOE) samples was determined to be up to 6, 9, 15 and 18 days respectively. The values of total volatile basic nitrogen, free fatty acid and thiobarbituric acid increased progressively during the storage period for all the treatments. However, the preservative methods applied led to an extended shelf life of fillets based on chemical indices and sensory attributes in the following order: VPSOE>VPS>APS>control group. The assay of the total viable count (TVC) revealed that 2% and 4%VPSOE produced a decrease in TVC throughout the storage period. According to the results obtained, the best method to preserve the mahi sefid fillet was by 4%VPSOE treatment. [source] A Recombinant Bacteriophage-Based Assay for the Discriminative Detection of Culturable and Viable but Nonculturable Escherichia coli O157:H7BIOTECHNOLOGY PROGRESS, Issue 3 2006Raheela Awais A previously green fluorescent protein (GFP)-labeled PP01 virulent bacteriophage, specific to Escherichia coli O157:H7, was used to construct lysozyme-inactivated GFP-labeled PP01 phage (PP01e - /GFP). The new recombinant phage lacked lytic activity because of the inactivation of gene e, which produces the lysozyme responsible for cell lysis. Gene e was inactivated by inserting an amber stop codon. Prolonged incubation ofE. coli O157:H7 cells with PP01e - /GFP did not lead to cell lysis, while the propagation of PP01e - /GFP in host cells increased the intensity of green fluorescence. Retention of cell morphology and increase in fluorescence enabled the direct visualization and enumeration of E. coli O157:H7 cells within an hour. The PP01e - /GFP system, when combined with nutrient uptake analysis, further allowed the discriminative detection of culturable, viable but nonculturable (VBNC), and dead cells in the stress-induced aquatic environment. Stress-induced cells, which retained culturability, allowed phage propagation and produced bright green florescence. Nonculturable cells (VBNC and dead) allowed only phage adsorption but no proliferation and remained low fluorescent. The low-fluorescent nonculturable cells were further differentiated into VBNC and dead cells on the basis of nutrient uptake analysis. The low-fluorescent cells, which grew in size by nutrient incorporation during prolonged incubation in nutrient medium, were defined as metabolically active and in the VBNC state. The elongated VBNC cells were then easily recognizable from dead cells. The proposed assay enabled the detection and quantification of VBNC cells. Additionally, it revealed the proportion of culturable to VBNC cells within the population, as opposed to conventional techniques, which demonstrate VBNC cells as a differential value of the total viable count and the culturable cell count. [source] Antimicrobial activity of varying concentrations of sodium hypochlorite on the endodontic microorganisms Actinomyces israelii, A. naeslundii, Candida albicans and Enterococcus faecalisINTERNATIONAL ENDODONTIC JOURNAL, Issue 7 2004C. E. Radcliffe Abstract Aim, To determine the resistance of microorganisms associated with refractory endodontic infections to sodium hypochlorite used as a root canal irrigant. Methodology, Two strains each of Actinomyces naeslundii, Candida albicans and Enterococcus faecalis were tested as late logarithmic phase inocula, against sodium hypochlorite adjusted to 0.5, 1.0, 2.5 and 5.25% w/v. Contact times used were 0, 10, 20, 30, 60 and 120 s. In the case of E. faecalis, additional experiments used contact times of 1.0, 2.0, 5.0, 10.0 and 30.0 min. Anti-microbial action was halted by sodium thiosulphate addition. Survivors were measured primarily using viable counts on drop plates. Additionally, pour plates were used to count low colony-forming units (cfu) and dilutions to 10,6 were used to count high cfu. Results, All concentrations of NaOCl lowered cfu below the limit of detection after 10 s in the case of A. naeslundii and C. albicans. However, E. faecalis proved to be more resistant to NaOCl. Using 0.5% NaOCl for 30 min reduced cfu to zero for both strains tested. This compares with 10 min for 1.0%, 5 min for 2.5% and 2 min for 5.25% (P < 0.001). Regression analysis for the dependent variable loge(count + 1) with loge(time + 1) and concentration as explanatory variables gave rise to a significant interaction between time and concentration (P < 0.001). Conclusion, The published association of E. faecalis with refractory endodontic infection may result, at least partially, from high resistance of this species to NaOCl. This does not appear to be the case with A. naeslundii or C. albicans. [source] Effect of probiotic Lactobacillus casei Zhang on fermentation characteristics of set yogurtINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 1 2010JICHENG WANG The effect of four inoculation levels of Lactobacillus casei Zhang (0.001, 0.01, 0.1 and 1.0 g/100 g) on the fermentation characteristics of set-style yogurt, and the changes in viable counts of lactic acid bacteria, pH value, syneresis, apparent viscosity, sugar and organic acid contents were determined during fermentation and storage over 21 days. The presence of 0.001 to 0.01 g/100 g L. casei Zhang did not affect the growth of the yogurt strains, and the yogurt inoculated with 0.00 1 g/100 g of L. casei Zhang had the highest apparent viscosity among the samples. However, a high inoculated level of L. casei Zhang (1.0 g/100 g) resulted in yogurts with inferior quality. [source] Preliminary investigation of the combined effect of heat treatment and incubation temperature on the viability of the probiotic micro-organisms in freshly made yogurtINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 1 2006A M MORTAZAVIAN The combined effects of heat treatment and incubation temperature were studied on the viability and fermentation time of probiotics in ABY 1 probiotic yogurt (Lactobacillus acidophilus, Bifidobacterium spp. and yogurt bacteria). Three levels of heat treatment (85°C for 30 min, 95°C for 5 min and 95°C for 15 min) and three levels of incubation temperature (37, 40 and 44°C) were selected. At the end of fermentation, the maximum viability of probiotics (for both L. acidophilus and Bifidobacterium spp.) was observed when the milk was heated at 95°C for 15 min and incubated at 37°C. Incubation time was only affected by the incubation temperature and, at 37°C, the longest incubation time of about 6 h was needed to achieve the highest viable counts of L. acidophilus and Bifidobacterium spp. [source] Decontamination of deboned chicken legs by vacuum-tumbling in lactic acid solutionINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2006François Deumier Summary Vacuum tumbling in a 1,5% lactic acid solution for a short time (1,10 min) improves the microbiological quality of deboned chicken legs, while inducing a light acidification and water absorption. The most significant variable of the process is the tumbling speed. High tumbling speeds lead to a high decontamination level of the chicken legs with regard to total viable counts and Enterobacteriaceae. Sodium lactate alone is unable to induce any decontamination at the same concentrations. Decontamination is probably more linked to acidification than to lactate ions. The use of vacuum tumbled (1 min in a 1% lactic acid solution) deboned chicken legs in the industrial manufacture of fresh chicken sausages led to a clear decrease in the number of Salmonella -positive batches. The incidence of positive batches was reduced threefold and the acid decontamination process did not adversely affect the sensory quality of the sausages. [source] Modelling the photosensitization-based inactivation of Bacillus cereusJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2009Y. Le Marc Abstract Aims:, To study and to develop a model for the photo-destruction of the foodborne pathogen Bacillus cereus, initially treated with a precursor of endogenous photosensitizers (5-aminolevulinic acid, ALA). Materials and methods:, The cells were incubated in the presence of ALA (3 or 7·5 mmol l,1) for incubation times ranging from 2 to 60 min, inoculated onto the surface of LB Agar plates and submitted to light irradiation. The Weibull model was used to describe the survival curves of B. cereus. Quadratic equations were used to describe the effects of ALA concentration and incubation time on the Weibull model parameters. Results:, ALA-based photosensitization proved to be an effective tool for inactivation of B. cereus. The decrease in viable counts observed after 20 min of irradiation, ranged from 4 to 6 log CFU g,1. Conclusions:, The developed model proved to be a parsimonious and robust solution to describe the observed data. Significance and Impact of the Study:, The study demonstrates the effectiveness of photosensitization on B. cereus on agar plates. The model developed may be useful to optimize inactivation treatments by photosensitization. [source] Inhibition of biofilms associated with dentures and toothbrushes by tetrasodium EDTAJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007D.A. Devine Abstract Aims:, We examined the efficacy of tetrasodium EDTA in eradicating biofilms derived from salivary inocula or pure cultures of Candida albicans on discs of polymethyl methacrylate (PMMA) denture base or on toothbrushes that had been used normally for 4,8 weeks. Its efficiency in virus neutralization was also determined. Methods and Results:, Overnight (16 h) treatment with 4% (w/v) tetrasodium EDTA solution reduced salivary and C. albicans biofilm viable counts by ,99%. Biofilm removal was confirmed using confocal laser scanning microscopy. Presence/absence of sucrose during biofilm formation had no effect on killing efficacy. Prolonged treatment of PMMA with tetrasodium EDTA did not influence subsequent formation of C. albicans biofilms or affect surface roughness of the PMMA, but it reduced subsequent biofilm formation from a salivary inoculum. Infectivities of herpes simplex virus and polio virus suspensions were reduced by >99·99% by treatment for 1 and 2 h, respectively. Conclusions:, Tetrasodium EDTA solution efficiently disinfected toothbrushes and PMMA discs, with the detachment of biofilms, and rapidly neutralized both nonenveloped and enveloped viruses. Significance and Impact of the Study:, Dentures and toothbrushes become contaminated by bacterial biofilms and by viruses. There is a need for disinfection methods that are rapidly effective, cost-effective, nontoxic and easily implemented. These studies indicate that tetrasodium EDTA solution has disinfection applications in the oral care field. [source] Formation of nonculturable Escherichia coli in drinking waterJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2005L.A. Bjergbæk Abstract Aims:, To examine whether incubation of Escherichia coli in nondisinfected drinking water result in development of cells that are not detectable using standard procedures but maintain a potential for metabolic activity and cell division. Methods and Results:, Survival and detectability of four different E. coli strains were studied using drinking water microcosms and samples from contaminated drinking water wells. Recovery of E. coli was compared using different cultivation-dependent methods, fluorescence in situ hybridization (FISH) using specific oligonucleotide probes, direct viable counts (DVC), and by enumeration of gfp -tagged E. coli (green fluorescent protein, GFP). Two levels of stress responses were observed after incubation of E. coli in nondisinfected drinking water: (i) the presence of cells that were not detected using standard cultivation methods but could be cultivated after gentle resuscitation on nonselective nutrient-rich media, and (ii) the presence of cells that responded to nutrient addition but could only be detected by cultivation-independent methods (DVC, FISH and GFP). Collectively, the experiments demonstrated that incubation for 20,60 days in nondisinfected drinking water resulted in detection of only 0·7,5% of the initial E. coli population using standard cultivation methods, whereas 1,20% could be resuscitated to a culturable state, and 17,49% could be clearly detected using cultivation-independent methods. Conclusions:, Resuscitation of stressed E. coli on nonselective nutrient-rich media increased cell counts in drinking water using both traditional (CFU), and cultivation-independent methods (DVC, FISH and GFP). The cultivation-independent methods resulted in detection of 10,20 times more E. coli than the traditional methods. The results indicate that a subpopulation of substrate-responsive but apparent nonculturable E. coli may develop in drinking water during long-term starvation survival. Significance and Impact of the Study:, The existence of substrate-responsive but nonculturable cells should be considered when evaluating the survival potential of E. coli in nondisinfected drinking water. [source] The formation of mixed culture biofilms of oral species along a gradient of shear stressJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2000K.A. Saunders A chemostat mixed culture system was used to produce two distinct ecological states, state-1 (caries-like microcosm) and state-2 (periodontal-like microcosm). Eleven bacterial species (Streptococcus gordonii, Strep. mitis I, Strep. mutans, Strep. oralis, Actinomyces naeslundii, Lactobacillus casei, Neisseria subflava, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella nigrescens, Veillonella dispar) were used to inoculate the planktonic system. A flow cell, designed to produce convergent flow with increasing shear stress, was attached to the chemostat system, and the resultant biofilms developed from the state-1 and state-2 microcosms along the shear stress gradient were examined and compared using image analysis and viable counts. The biofilm produced from state-1 showed a lower shear stress tolerance (0·146 Pa) than the state-2 biofilm (0·236 Pa). The biofilm compositions did not vary along the gradient of shear stress and were dependent on the initial inoculum conditions. Gram-positive species were predominant in the state-1 biofilm, while Gram-negative species were predominant in state-2. [source] Antibacterial activity of dental composites containing zinc oxide nanoparticles,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2010Berdan Aydin Sevinç Abstract The resin-based dental composites commonly used in restorations result in more plaque accumulation than other materials. Bacterial biofilm growth contributes to secondary caries and failure of resin-based dental composites. Methods to inhibit biofilm growth on dental composites have been sought for several decades. It is demonstrated here that zinc oxide nanoparticles (ZnO-NPs) blended at 10% (w/w) fraction into dental composites display antimicrobial activity and reduce growth of bacterial biofilms by roughly 80% for a single-species model dental biofilm. Antibacterial effectiveness of ZnO-NPs was assessed against Streptococcus sobrinus ATCC 27352 grown both planktonically and as biofilms on composites. Direct contact inhibition was observed by scanning electron microscopy and confocal laser scanning microscopy while biofilm formation was quantified by viable counts. An 80% reduction in bacterial counts was observed with 10% ZnO-NP-containing composites compared with their unmodified counterpart, indicating a statistically significant suppression of biofilm growth. Although, 20% of the bacterial population survived and could form a biofilm layer again, 10% ZnO-NP-containing composites maintained at least some inhibitory activity even after the third generation of biofilm growth. Microscopy demonstrated continuous biofilm formation for unmodified composites after 1-day growth, but only sparsely distributed biofilms formed on 10% ZnO-NP-containing composites. The minimum inhibitory concentration of ZnO-NPs suspended in S. sobrinus planktonic culture was 50 ,g mL,1. ZnO-NP-containing composites (10%) qualitatively showed less biofilm after 1-day-anaerobic growth of a three-species initial colonizer biofilm after being compared with unmodified composites, but did not significantly reduce growth after 3 days. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. [source] Soybean meal alters autochthonous microbial populations, microvilli morphology and compromises intestinal enterocyte integrity of rainbow trout, Oncorhynchus mykiss (Walbaum)JOURNAL OF FISH DISEASES, Issue 9 2009D L Merrifield Abstract Rainbow trout were fed either a diet containing fishmeal (FM) as the crude protein source or a diet containing 50% replacement with soybean meal (SBM) for 16 weeks. An enteritis-like effect was observed in the SBM group; villi, enterocytes and microvilli were noticeably damaged compared with the FM group. The posterior intestine microvilli of SBM-fed fish were significantly shorter and the anterior intestine microvilli significantly less dense than the FM-fed fish. Electron microscopy confirmed the presence of autochthonous bacterial populations associated with microvilli of both fish groups. Reduced density of microvilli consequently led to increased exposure of enterocyte tight junctions, which combined with necrotic enterocytes is likely to diminish the protective barrier of the intestinal epithelium. No significant differences in total viable counts of culturable microbial populations were found between the groups in any of the intestinal regions. A total of 1500 isolates were tentatively placed into groups or genera, according to standard methods. Subsequent partial 16S rRNA sequencing revealed species that have not been identified from the rainbow trout intestine previously. Compared with the FM group levels of Psychrobacter spp. and yeast were considerably higher in the SBM group; a reduction of Aeromonas spp. was also observed. [source] GROWTH AND CHARACTERIZATION OF THE HISTAMINE-FORMING BACTERIA OF JACK MACKEREL (TRACHURUS SYMMETRICUS)JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2003ALINA BERMEJO ABSTRACT Consumption of fish with high histamine poses health hazards. The isolation, identification and viable counts of the histamine-forming bacteria from jack mackerel in batch cultures in trypticase soy broth with 2 % histidine at 25, 15 and 5C were performed. Proteus vulgaris, Aeromonas hydrophila and Photobacterium damsela were the most histamine producing population. The community had a maximal specific growth rate (,max) of 0.304, 0.217 and 0.048 h,1 at 25, 15 and 5C, respectively. Mulchandani's model, with an exponential value of 5.21, predicted bacterial growth. Histamine production was proportional to growth rate; proportionality coefficients were 1.987, 0.436 and 1.439 and the community's maximal spefic rates for histamine production were 0.604, 0.095 and 0.068 [g histamine (g dry cells h),1] af 25, 15 and SC, respectively. Lesser histamine production at 15C needs further investigation in whole fish, as it is a relevant result forfish handling. [source] Improving the Stability of Probiotic Bacteria in Model Fruit Juices Using Vitamins and AntioxidantsJOURNAL OF FOOD SCIENCE, Issue 5 2010N.P. Shah Abstract:, This study examined the survival of probiotic bacteria in a model fruit juice system. Three different strains of probiotic bacteria were used in this study: HOWARU,Lactobacillus rhamnosus,HN001, HOWARU,Bifidobacterium lactis,HN001, and,Lactobacillus paracasei,LPC 37. The probiotic bacteria were inoculated into model juice with various vitamins and antioxidants, namely white grape seed extract, green tea extract, vitamin B2, vitamin B3, vitamin B6, vitamin C, and vitamin E. The model juice without any additives was used as a control. Their viability was assessed on a weekly basis using plate count method. The model juice was made with sucrose, sodium citrate, citric acid powder, and distilled water and was pasteurized before use. Our findings showed that probiotic bacteria did not survive well in the harsh environment of the model fruit juice. However, the model juice containing vitamin C, grape extract, and green tea extract showed better survival of probiotic bacteria. The model juice containing grape seed extract, green tea extract, and vitamin C had the same initial population of 8.32 log CFU/mL, and at the end of the 6-wk storage period it had an average viability of 4.29 log CFU/mL, 7.41 log CFU/mL, and 6.44 log CFU/mL, respectively. Juices containing all other ingredients tested had viable counts of <10 CFU/mL at the end of the 6-wk storage period. [source] Effect of Thawing and Cold Storage on Frozen Chicken Thigh Meat Quality by High-Voltage Electrostatic FieldJOURNAL OF FOOD SCIENCE, Issue 4 2010Chang-Wei Hsieh ABSTRACT:, One of the most popular issues in electrostatic biology is the effects of a high-voltage electrostatic field (HVEF) on the thawing of chicken thigh meat. In this study, chicken thigh meat was treated with HVEF (E-group), and compared to samples stored in a common refrigerator (R-group), to investigate how HVEF affects chicken thigh meat quality after thawing at low temperature storage (,3 and 4 °C). The results showed that there were no significant differences in biochemical and microorganism indices at ,3 °C. However, the HVEF can significantly shorten thawing time for frozen chicken thigh meat at ,3 °C. After thawing chicken thigh meat and storing at 4 °C, the total viable counts reached the Intl. Commission on Microbiological Specification for Foods limit of 107 CFU/g on the 6 and 8 d for the R- and E-group, respectively. On the 8th d, the volatile basic nitrogen had increased from 11.24 mg/100 g to 21.9 mg/100 g for the E-group and 39.9 mg/100 g for the R-group, respectively. The biochemical and microorganism indices also indicated that the E-group treatment yielded better results on thawing than the R-group treatment. The application of this model has the potential to keep products fresh. [source] Use of Lysozyme, Nisin, and EDTA Combined Treatments for Maintaining Quality of Packed Ostrich PattiesJOURNAL OF FOOD SCIENCE, Issue 3 2010Marianna Mastromatteo ABSTRACT:, The antimicrobial effectiveness of lysozyme, nisin, and ethylene diamine tetraacetic acid (EDTA) combination treatments (Mix1: 250 ppm lysozyme, 250 ppm nisin, 5 mM EDTA; Mix2: 500 ppm lysozyme, 500 ppm nisin, 5 mM EDTA) on bacterial growth of ostrich patties packaged in air, vacuum, and 2 different modified atmospheres (MAP1: 80% O2, 20% CO2; MAP2: 5% O2, 30% CO2, 65% N2) was evaluated. Moreover, the lipid oxidation was evaluated as well as color and sensory characteristics. The growth of total viable counts and lactic acid bacteria were strongly inhibited by the antimicrobial treatments in all the running time (Inhibition Index >97%) whereas for Enterobacteriaceae,and Pseudomonas,spp. lower inhibition indices from 12% to about 28% were observed. The lipid oxidation was more pronounced in the control respect to the treated meat patties. Moreover, the mixture at low concentration of lysozyme and nisin showed the best antioxidative effect. High concentrations of lysozyme and nisin showed the greatest color loss. Also, off-odors for the untreated patties developed faster than the treated samples. Practical Application: Great interest is developing in food bio-preservation, because of the ever-increasing needs to protect consumers' health and to valorize the naturalness and safety of food products. [source] Effect of Lactulose on Biotransformation of Isoflavone Glycosides to Aglycones in Soymilk by LactobacilliJOURNAL OF FOOD SCIENCE, Issue 3 2008T.T. Pham ABSTRACT:,Lactobacillus acidophilus 4461, L. acidophilus 4962, L. casei 290, and L. casei 2607 were used to hydrolyze isoflavone glycosides (IG) to biologically active forms,isoflavone aglycones (IA),in soymilk (SM) prepared from soy protein isolate (SPI) and soymilk supplemented with 0.5% (w/v) of lactulose (SML). L. acidophilus 4461 utilized the highest level of lactulose (3.01 mg/mL) and L. acidophilus 4962 utilized the least (0.86 mg/mL) at 24 h of incubation. The pH values decreased to 4.00 to 5.00 in SML, while they remained relatively high (6.15 to 6.36) in SM. Supplementation with lactulose significantly (P < 0.05) enhanced the viable counts of all the 4 Lactobacillus strains. At the end of incubation, the viable counts of Lactobacillus ranged from 8.08 to 8.25 log CFU/mL in SML compared to 6.99 to 7.11 log CFU/mL in SM. Supplementation with lactulose increased the biotransformation of IG to IA after 6 h of incubation. The presence of lactulose in the medium enhanced the biotransformation level of IG to IA by Lactobacillus up to 21.9%. The hydrolysis level of malonyl genistin and acetyl genistin in SML was much higher than in SM by all the 4 probiotic organisms. The biotransformation of IG to IA occurred rapidly during the 1st 12 h of incubation in both SML and SM. Among the 4 Lactobacillus strains, L. acidophilus 4461 biotransformed the highest level (88.8%) of IG to IA in SML compared to 68.2% in SM after 24 h of incubation. [source] Prediction of Microbial and Sensory Quality of Cold Smoked Atlantic Salmon (Salmo salar) by Electronic NoseJOURNAL OF FOOD SCIENCE, Issue 9 2005Gudrun Olafsdottir ABSTRACT: Quality changes of cold smoked salmon from 4 different smokehouses in Europe were monitored by a prototype gas-sensor array system, the FishNose. Samples were stored in different packaging (vacuum and Modified Atmosphere Packaging [MAP]) for up to 4 wk under controlled storage conditions at 5 °C and 10 °C. Quality criteria based on sensory attributes (sweet/sour, off, and rancid odor), and total viable counts and lactic acid bacteria counts were established and used for classification of samples based on the responses of the FishNose. The responses of the gas-sensors correlated well with sensory analysis of spoilage odor and microbial counts suggesting that they can detect volatile microbially produced compounds causing spoilage odors in cold-smoked salmon during storage. The system is therefore ideal for fast quality control related to freshness evaluation of smoked salmon products. Partial least squares (PLS) regression models based on samples from single producer showed better performance than a global model based on products from different producers to classify samples of different quality. [source] | |||||||||||||||||||