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CFU G (cfu + g)
Kinds of CFU G Selected AbstractsThymol and modified atmosphere packaging to control microbiological spoilage in packed fresh cod hamburgersINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2009Maria Rosaria Corbo Summary A study on the use of mild technologies to produce packaged fish hamburgers was presented. In particular, the antimicrobial effect of some natural compounds (carvacrol, eugenol, thymol, green tea extract, rosemary extract, grapefruit seed extract and lemon extract), at various concentrations (500,10 000 ppm), was screened in vitro against the main fish spoilage micro-organisms (Shewanella putrefaciens and Photobacterium phosphoreum). Lemon extract and thymol, in combination with modified atmosphere packaging, showed the greatest inhibition activity, therefore, thymol was subsequently used as an ingredient for producing fish hamburgers. Results pointed out that this combination is effective in controlling the growth of microbial species mainly involved in fresh fish spoilage; in particular, it significantly (P < 0.05) reduced the growth rate of bacterial population, performing about 4.8 log CFU g,1 and 6.5 log CFU g,1 reduction of the hydrogen sulphide producing bacteria and psychrotrophic aerobic specific spoilage organisms cell load, respectively, if compared with the control. [source] Quality changes of farmed blackspot seabream (Pagellus bogaraveo) subjected to slaughtering and storage under flow ice and ozonised flow iceINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2009Victoria Álvarez Summary Flow ice (FI) combined with ozone (OFI condition) was evaluated for slaughter and storage of farmed blackspot seabream (Pagellus bogaraveo) when compared with FI alone (FI condition). When processed in either OFI or FI conditions, this species exhibited slow biochemical and microbiological spoilage mechanisms when compared with other commercial fish species. The presence of ozone slowed down microbial development (1.00,3.53 and 1.60,4.04 log CFU g,1 for fish mesophile counts from OFI and FI conditions, respectively) and trimethylamine formation, so that fish kept under OFI condition was still acceptable at the end of the experiment (day 16), while its counterpart fish treated with FI was rejectable. In contrast, a small pro-oxidant effect could be assessed by means of the ozone presence; however, oxidation values (peroxide value and thiobarbituric acid index) reached at day 16 by individuals treated under OFI conditions (8.34 and 0.19, respectively) cannot be considered specially high. [source] Selecting for development of fluoroquinolone resistance in a Campylobacter jejuni strain 81116 in chickens using various enrofloxacin treatment protocolsJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2010K. Stapleton Abstract Aims:, To determine the effect of various enrofloxacin dose regimes on the colonization and selection of resistance in Campylobacter jejuni strain 81116P in experimentally colonized chickens. Methods and Results:, Two experiments were undertaken, in which 14-day-old chickens were colonized with 1 × 107,1 × 109 CFU g,1Camp. jejuni strain 81116P and then treated with enrofloxacin at 12,500 ppm in drinking water for various times. Caecal colonization levels were determined at various time-points after start-of-treatment, and the susceptibility of recovered isolates to ciprofloxacin was monitored. Resistance was indicated by growth on agar containing 4 ,g ml,1 ciprofloxacin, MICs of 16 ,g ml,1 and the Thr86Ile mutation in gyrA. Enrofloxacin at doses of 12,250 ppm reduced Camp. jejuni colonization over the first 48,72 h after start-of-treatment. The degree of reduction in colonization was dose, but not treatment time, dependent. In all cases, maximal colonization was re-established within 4,6 days. Fluoroquinolone-resistant organisms were recoverable within 48 h of start-of-treatment; after a further 24 h all recovered isolates were resistant. In contrast, a dose of 500 ppm enrofloxacin reduced colonization to undetectable levels within 48 h, and the treated birds remained Campylobacter negative throughout the remaining experimental period. By high pressure liquid chromatography, for all doses, the maximum concentrations of enrofloxacin and ciprofloxacin in the caecal contents were detected at the point of treatment completion. Thereafter, levels declined to undetectable by 7 days post-treatment withdrawal. Conclusions:, In a model using chickens maximally colonized with Camp. jejuni 81116P, treatment with enrofloxacin, at doses of 12,250 ppm in drinking water, enables the selection, and clonal expansion, of fluoroquinolone-resistant organisms. However, this is preventable by treatment with 500 ppm of enrofloxacin. Significance and impact of the study:, Treatment of chickens with enrofloxacin selects for resistance in Camp. jejuni in highly pre-colonized birds. However, a dose of 500 ppm enrofloxacin prevented the selection of resistant campylobacters. [source] The effect of Pediococcus acidilactici on the gut microbiota and immune status of on-growing red tilapia (Oreochromis niloticus)JOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2010R.M.W. Ferguson Abstract Aim:, To assess Pediococcus acidilactici as a dietary supplement for on-growing red tilapia (Oreochromis niloticus). Methods and Results:, Tilapia were fed either a control diet or control diet supplemented with Ped. acidilactici at 107 CFU g,1 for 32 days. Ped. acidilactici colonized the intestinal tract and significantly affected the intestinal microbial communities. PCR-DGGE revealed direct antagonism of gastric Ped. acidilactici with an endogenous uncultured bacterium during a period of reverting to nonsupplemented feeding. Light microscopy revealed that gut integrity and leucocyte levels were unaffected by Ped. acidilactici; however, blood leucocyte levels and serum lysozyme activity were elevated after 14-days' feeding. No significant improvements in growth performance were observed at the end of the trial (day 32), but survival was significantly higher in the probiotic group. Conclusions:, The study demonstrates that oral supplementation of Ped. acidilactici modulates intestinal bacterial communities in on-growing red tilapia and also stimulates some aspects of the nonspecific immune response. Significance and Impact of the study:, To our knowledge this is the first study assessing the effects of probiotics on the gut microbiota of tilapia using culture-independent methods. Such methods are crucial to understand the mechanisms which underpin and mediate host benefits. [source] Survival and spread of Shiga toxin-producing Escherichia coli in alpine pasture grasslandsJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2010B. Fremaux Abstract Aims:, To determine the fate of Shiga toxin-producing Escherichia coli (STEC) strains defecated onto alpine grassland soils. Methods and Results:, During the summers of 2005 and 2006, the field survival of STEC was monitored in cowpats and underlying soils in four different alpine pasture units. A most probable number (MPN)-PCR stx assay was used to enumerate STEC populations. STEC levels ranged between 3·9 and 5·4 log10 CFU g,1 in fresh cowpats and slowly decreased until their complete decay (inactivation rates k < 0·04 day,1). PFGE typing of STEC strains isolated from faecal and soil samples assessed the persistence of various clonal types for at least 2 months in cowpats and their vertical dispersal down through the soil at a depth up to at least 20 cm. STEC cells counts in soil were always below 2 log10 CFU g,1, regardless of the pasture unit investigated. The soil became rapidly free of detectable STEC once the cowpat had decomposed. The eight STEC strains isolated during this study belonged to six distinct serotypes and tested positive for the gene(s) stx2, including the stx2g and stx2 NV206 variants. Conclusions:, STEC were able to persist in cowpats and disseminate down through the soil but were unable to establish. Significance and impact of the Study:, This study provides useful information concerning the ecology of STEC in alpine pasture grasslands and may have implications for land and cattle management. [source] Detection of viable Escherichia coli O157:H7 by ethidium monoazide real-time PCRJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2009L. Wang Abstract Aims:, The aim of this study was to develop and optimize a novel method that combines ethidium bromide monoazide (EMA) staining with real-time PCR for the detection of viable Escherichia coli O157:H7 in ground beef. EMA can penetrate dead cells and bind to intracellular DNA, preventing its amplification via PCR. Methods and Results:, Samples were stained with EMA for 5 min, iced for 1 min and exposed to bright visible light for 10 min prior to DNA extraction, to allow EMA binding of the DNA from dead cells. DNA was then extracted and amplified by TaqMan® real-time PCR to detect only viable E. coli O157:H7 cells. The primers and TaqMan® probe used in this study target the uidA gene in E. coli O157:H7. An internal amplification control (IAC), consisting of 0·25 pg of plasmid pUC19, was added in each reaction to prevent the occurrence of false-negative results. Results showed a reproducible application of this technique to detect viable cells in both broth culture and ground beef. EMA, at a final concentration of 10 ,g ml,1, was demonstrated to effectively bind DNA from 108 CFU ml,1 dead cells, and the optimized method could detect as low as 104 CFU g,1 of viable E. coli O157:H7 cells in ground beef without interference from 108 CFU g,1 of dead cells. Conclusions:, EMA real-time PCR with IAC can effectively separate dead cells from viable E. coli O157:H7 and prevent amplification of DNA in the dead cells. Significance and Impact of the Study:, The EMA real-time PCR has the potential to be a highly sensitive quantitative detection technique to assess the contamination of viable E. coli O157:H7 in ground beef and other meat or food products. [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] Leaching of bioluminescent Escherichia coli O157:H7 from sheep and cattle faeces during simulated rainstorm eventsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2008A.P. Williams Abstract Aims:, Development of a novel inoculation technique to improve the current methods of determining the leaching of Escherichia coli O157:H7 from faeces. Methods and Results:, Ruminant faeces were inoculated with a high [c. 107 colony forming units (CFU) g,1] or low (c. 104 CFU g,1) load of a lux- marked strain of E. coli O157:H7 via injection, and subjected to four simulated heavy rainfall events. The population density and metabolic activity of E. coli O157:H7 recovered within the leachate was determined following each simulated rain event and compared with the indigenous E. coli population. The concentration of E. coli O157:H7 in the leachates followed a similar trend to that of nonpathogenic E. coli. Significantly greater densities of generic and pathogenic E. coli were recovered in the leachates generated from sheep faeces compared with cattle faeces. Pathogen metabolic activity was also significantly greater in sheep faeces. Conclusions:, Our findings show that E. coli O157:H7 may readily leach from ruminant faeces during rain events. The bacterium leaches more freely from sheep faeces than from cattle faeces and displays greater metabolic activity within sheep leachate. Significance and Impact of the Study:, A novel inoculation technique was developed that allowed the determination of both population density and cellular activity of E. coli O157:H7 in leachate derived from faeces. [source] Bacteriological and chemical changes occurring in Bunker-stored silage covered with biodegradable coatingJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2007P. Denoncourt Abstract Aims:, To evaluate the efficacy of a biodegradable silage coating for the ability to protect timothy (Phleum pratensa) type silage against spoilage and its quality under natural conditions. Methods and Results:, Triplicate mini-silos of silage were prepared for three treatments (1: uncoated; 2: coated with biodegradable coating and 3: sealed with plastic), two types of storage (unprotected or protected from rain) and 10 sampling times (0, 7, 14, 21, 28, 35, 42, 56, 63 and 70 days postensiling). Triplicate mini-silos were opened at each sampling time for microbiological (total aerobic bacteria, lactic acid bacteria, moulds and yeasts) and biochemical analyses [pH, dry matter (DM), water-soluble sugars (WSC), lactic (LA), acetic, propionic and butyric acids content]. The study showed that at day 70, counts of moulds and yeasts in silages protected against rain and coated with biodegradable coating were 5·98 log CFU g,1 when compared with 5·92 and 3·62 log CFU g,1 in samples from plastic-sealed silage and uncoated silage, respectively. The pH was low and stable pH (4·34) when compared with uncoated (7·17) and plastic sealed (8·34) silages (P 0·05). A DM, WSC and LA content of 421·7, 13·4 and 20·9 g kg,1 was, respectively, observed. For silage stored outdoors, a level of moulds and yeasts of 3·77 log CFU g,1 of silage was also observed in silages coated with biodegradable coating after 28 days of storage. A stable pH showing a mean value of 4 was also observed. The pH, DM, WSC and LA content were, respectively, 4·18, 341·1, 13·34 and 31·8 g kg,1 in these samples. After 70 days of storage, the level of moulds and yeasts on silage sealed with biodegradable coating was 7·73 log CFU g,1. A DM, WSC and LA content of 291·9, 5·56 and 10·0 g kg,1 was, respectively, observed. Conclusions:, When compared with uncoated silage, the application of biodegradable coating can preserve the quality of silage for up to a month when exposed to rain and up to 70 days when protected from rain. Significance and Impact of the Study:, Results emphasize the possibility of the use of a biodegradable coating as an alternative to plastic film for sealing horizontal bunker silos. [source] Transmission of cotton seed and boll rotting bacteria by the southern green stink bug (Nezara viridula L.)JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2007E.G. Medrano Abstract Aims:, To determine the ability of the southern green stink bug (SGSB) (Nezara viridula L.) to transmit Pantoea agglomerans into cotton (Gossypium hirsutum) bolls. Methods and Results:, An SGSB laboratory colony was kept on fresh green beans. A P. agglomerans variant resistant to rifampicin (Rif) (strain Sc 1-R) was used as the opportunistic cotton pathogen. Adult insects were individually provided green beans that were sterilized and then soaked in either sterile water or in a suspension of strain Sc 1-R. Insects were individually caged with an unopened greenhouse-grown cotton boll. After 2 days, live SGSB were collected, surfaced sterilized, ground, serially diluted, and then plated on nonselective media and media amended with Rif. Exterior and interior evidence of feeding on bolls was recorded 2 weeks after exposure to insects. Seed and lint tissue were harvested, ground, serially diluted, and then plated on media with and without Rif. Bacteria were recovered on nonselective media from all insects, and from seed and lint with signs of insect feeding at concentrations ranging from 102 to 109 CFU g,1 tissue. The Sc 1-R strain was isolated only from insects exposed to the marked strain and from seed and lint of respective bolls showing signs of insect feeding. Evidence of insect feeding on the exterior wall of the carpel was not always apparent (47%), whereas feeding was always observed (100%) on the interior wall in association with bacterial infections of seed and lint. Conclusions:,Nezara viridula readily ingested the opportunistic P. agglomerans strain Sc 1-R and transmitted it into unopened cotton bolls. Infections by the transmitted Sc 1-R strain caused rotting of the entire locule that masked internal carpel wounds incurred by insect feeding. Bacteria were recovered from penetration points by insects not exposed to the pathogen, but locule damage was limited to the area surrounding the feeding site (c. 3 mm). Significance and Impact of the Study:, This is the first study that demonstrates the ability of SGSB to acquire and transmit plant pathogenic bacteria into cotton bolls. [source] Fate of inoculated Escherichia coli in hayJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007Z.G. Weinberg Abstract Aims:, To monitor the fate of inoculated Escherichia coli in dry and moist hay of various types, under laboratory conditions. Methods and Results:, Wheat, vetch and clover hay were used as received or wetted to 250,300 g kg,1 moisture. The hay was inoculated at about 106 CFU g,1 with a kanamycin-resistant E. coli strain that expresses the green fluorescence protein, and was stored in small open glass jars that were covered with aluminium foil. Three jars per treatment were sampled on days 1 and 3, or 4 and 7, or 8, 20 and 50, respectively, after the initiation of the experiments, and the numbers of E. coli in the hay were determined. The results indicated that E. coli disappeared from both dry and moist hay by 7,8 days after inoculation. However, in a few cases colonies that were presumed to be E. coli developed after incubation in Luria broth medium. Conclusions:, The tagged E. coli strain usually disappeared rapidly from both the dry and the moist hay, in spite of the high level of inocula used. However, in some cases a few, possibly injured E. coli might have persisted, and could be detected after incubation in a rich growth medium. Significance and Impact of the Study:, This study is part of a risk assessment associated with sewage irrigation of forage crops in Israel. The results indicate that E. coli added to the hay is not likely to pose a health risk to cattle or to humans. Nevertheless, more research with natural strains of E. coli and other enteric pathogens that might be more adapted to forage conditions is warranted in order to ensure the safety of sewage-irrigated crops. [source] Enumeration of Campylobacter spp. on the surface and within chicken breast filletsJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2007P. Luber Abstract Aim:, To investigate how many Campylobacter bacteria are present on the surface and inside chicken breast fillets, with a focus on generating data distributions which can be used in risk assessments for this pathogen,commodity combination. Methods and Results:, We analysed 100 fresh retail chicken breast fillets (skinless and deboned) by means of a rinse sample for surface and 55 fillets for internal pathogen contamination using 10 g meat and a most probable number technique. Prevalence was 87% on the surface and 20% in the deep tissue. The mean number of Campylobacter on the surface of the fillets was 1903 CFU, with a median of 537 CFU and a maximum of 38 905 CFU. Campylobacter counts inside the tissue were <1 CFU g,1 meat (mean = 0·24 CFU, median = 0·15 CFU, maximum = 0·74 CFU). In addition, we investigated the influence of the type of package on the occurrence of the pathogen. Data provide an indication of less favourable conditions for survival of the pathogen on chicken meat packed under a modified atmosphere of carbon dioxide in nitrogen, in comparison with ambient air or vacuumed packages. Conclusions:, Given the high numbers of the pathogen on the chicken meat surface in comparison with low levels of internal contamination, it can be concluded that cross-contamination during the preparation of contaminated chicken is a more important pathway for consumers' exposure to Campylobacter than the consumption of undercooked meat. Significance and Impact of the Study:, The detailed quantitative data on the occurrence of C. jejuni and C. coli on the surface and inside chicken meat presented here can be useful for future probabilistic exposure assessments. [source] Combination of a urease inhibitor and a plant essential oil to control coliform bacteria, odour production and ammonia loss from cattle wasteJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2007V.H. Varel Abstract Aim:, To evaluate urea hydrolysis, volatile fatty acid (VFA) production (odour) and coliforms in cattle waste slurries after a urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) and a plant oil component (thymol) were added. Methods and Results:, Faeces from cattle fed a diet of 70% corn silage and 30% alfalfa haylage, urine and distilled water in the ratio 50 : 35 : 15 were blended at high speed for 1 min. Triplicate aliquots of 750 ml were amended with NBPT plus or minus thymol and reblended for 1 min, and were poured into 1·6 l wide-mouth jars covered 90% with a lid. After 56 days, thymol (2000 mg kg,1 waste) in combination with NBPT (80 mg kg,1 waste) retained 5·2 g of an initial 9·2 g of urea in cattle waste slurries, compared with less than 1 g of urea retained when NBPT was the only additive (P < 0·05). Another experiment using excreta from cattle fed 76·25% high moisture corn, 19·25% corn silage and a 4·5% supplement, blended at a low speed, gave a similar response with urea hydrolysis; and the two treatments, thymol alone and thymol in combination with NBPT, reduced VFA production (P < 0·01) and eliminated all coliform bacteria by day 1. A third experiment indicated coliforms disappeared in the no addition treatment after 8 days; however, they were viable at 6·6 × 104 CFU g,1 waste beyond 35 days in the NBPT treatment. Conclusions:, Thymol supplements the effect of NBPT by increasing the inhibitory period for hydrolysis of urea in cattle waste slurries and nitrogen retention in the waste. Significance and Impact of the Study:, Thymol and NBPT offer the potential to reduce odour and pathogens in cattle manure, and increase the fertilizer value. [source] Growth and survival of non-O157:H7 Shiga-toxin-producing Escherichia coli in cow manureJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2007B. Fremaux Abstract Aims:, The main objective of this study was to evaluate the behaviour of non-O157:H7 Shiga-toxin-producing Escherichia coli (STEC) strains in cow manure. Methods and Results:, A mixture of eight green-fluorescent-protein-labelled STEC strains was inoculated around 106,107 CFU g,1 into four manure heaps. Two heaps were regularly turned and the two others remained unturned. STEC counts and physical parameters (temperature, pH, moisture content and oxido-reduction potential) were monitored for 1000 manure samples. The highest mean pH values were obtained near the surface at the base of all manure heaps. At the surface, the moisture content decreased from 76·5% to 42% in turned heaps. Temperatures reached 65°C near the main body of all manure heaps, and only 35°C near the superficial parts located at the base of them. These two sites (the centre and the base) were associated with D values for the STEC counts of 0·48 and 2·39 days, respectively. We were able to detect STEC strains during 42 days in turned manure heaps and during at least 90 days in unturned ones. Conclusions:, These results emphasize the long-term survival of non-O157:H7 STEC in cow manure. Significance and Impact of the Study:, Good management practices (e.g. turning) should be respected in order to minimize the risk of environmental contamination by STEC. [source] An updated review of Listeria monocytogenes in the pork meat industry and its productsJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2006D. Thévenot Abstract Pork meat and processed pork products have been the sources of outbreaks of listeriosis in France and in other European countries during the last decade. The aim of this review is to understand how contamination, survival and growth of Listeria monocytogenes can occur in pork meat products. This study discusses the presence of L. monocytogenes in raw pork meat, in the processing environment and in finished products. The prevalence of L. monocytogenes generally increases from the farm to the manufacturing plants and this mainly due to cross-contamination. In many cases, this pathogen is present in raw pork meat at low or moderate levels, but foods involved in listeriosis outbreaks are those in which the organism has multiplied to reach levels significantly higher than 1000 CFU g,1. In such cases, L. monocytogenes has been able to survive and/or to grow despite the hurdles encountered during the manufacturing and conservation processes. Accordingly, attention must be paid to the design of food-processing equipment and to the effectiveness of the cleaning and disinfecting procedures in factories. Finally, the production of safe pork meat products is based on the implementation of general preventive measures such as Good Hygiene Practices, Good Manufacturing and the Hazard Analysis Critical Control Point. [source] Bacillus cereus is common in the environment but emetic toxin producing isolates are rareJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2006M. Altayar Abstract Aims:, To determine the incidence of emetic toxin producing Bacillus cereus in soil, animal faeces and selected vegetable produce to compare the results with the previously reported high incidence in rice paddy fields. To examine whether the emetic toxin has antibiotic activity. Methods and Results:, The incidence of emetic toxin producing B. cereus was evaluated by plating on selective agar 271 samples of soils, animal faeces, raw and processed vegetables. Overall, 45·8% of samples were positive for B. cereus. One hundred and seventy-seven B. cereus isolates were recovered at 30°C with the grand mean spore count being 2·6 ± 1·7 log10 CFU g,1 and 148 B. cereus isolates were recovered at 7°C with the grand mean spore count being 2·2 ± 1·2 log10 CFU g,1 of the177 B. cereus isolated at 30°C, only 3 were positive for emetic toxin production at a titre of 1/64, 1/32, 1/16, respectively. Also, 1 of 148 B. cereus isolated at 7°C was positive for emetic toxin production to a titre of 1/128. All positive isolates came from washed or unwashed potato skins, one was psychrotrophic as determined by PCR and growth at 7°C on subculture. The emetic toxin was not shown to have any antibiotic effects in growth inhibition studies. Conclusions:, While B. cereus was a common isolate, the incidence of the emetic strain was rare. This is in contrast to previous findings of the high incidence in rice paddy fields and the processing environment, which may suggest rice is a selective area for growth of the emetic strain of B. cereus. Significance and Impact of Study:, The finding that a psychrotrophic isolate of B. cereus can produce emetic toxin is the first ever such observation and suggests the possibility that psychrotrophic isolates could grow in refrigerated fresh foods and cause emesis. The incidence of emetic B. cereus strains in rice paddy fields now requires further study for comparison with the low incidence found in other soils. The emetic toxin failed to inhibit the growth of other bacterial, fungal and yeast species. Whether the toxin (which is similar in structure to the antibiotic valinomycin) plays a competitive role in the environment therefore remains unclear. [source] Decrease of enteric micro-organisms from rural sewage sludge during their composting in straw mixtureJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2005A.-M. Pourcher Abstract Aims:, To study the decrease of enteric micro-organisms including viable nematode eggs, enteroviruses, faecal indicators (Escherichia coli and enterococci) and pathogenic bacteria (Listeria monocytogenes, Salmonella sp. and Clostridium perfringens) of a rural sewage sludge when it is composted for 7 months in mixture with straw. Methods and Results:, Numbers of the test organisms and the physico-chemical parameters were measured on a monthly basis on the mixture, on the compost after being turned, and on the pile in three positions representing the part by which air is incoming, the bottom of the pile and the part through which air is outgoing. The lowest temperature in the pile was observed at the bottom, where it did not exceed 50°C against 66°C in the two other areas. There were no significant differences between the three areas in terms of micro-organism survival. Infectious enteroviruses were inactivated rapidly and were not found after the first turning whereas some genomes were detected until after the third turning. Escherichia coli and enterococci presented a similar survival rate and their number decreased by 4 log10 whereas Salmonella decayed at a greater rate than L. monocytogenes. The numbers of C. perfringens decreased gradually to reach a final concentration in the mature compost of about 102 CFU g,1 dry matter (d.m.), which was similar to that of the faecal indicators. Conclusions:, The hygienic effect of sludge composting in mixture with straw results in a significant reduction of enteric micro-organisms, the concentration of the faecal indicators in the final product being <64 most probable number g,1 d.m. The concentrations of Salmonella, enteroviruses and viable nematode eggs in the final product were not detectable which is in accordance with the French legislation. Significance and Impact of the Study:, The results which pointed out the different behaviour of the test micro-organisms reflect the difficulty to propose a relevant indicator of hygienization. Otherwise, they show that composting is an efficient means for hygienization of sludge of rural wastewater treatment, where the straw is available close to their place of production. [source] Inactivation of Staphylococcus aureus in raw milk cheese by combinations of high-pressure treatments and bacteriocin-producing lactic acid bacteriaJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2005J.L. Arqués Abstract Aims:, To investigate the combined effect of high-pressure treatments (HPT) and milk inoculation with bacteriocin-producing lactic acid bacteria (BP-LAB) on the survival of Staphylococcus aureus during ripening of raw milk cheese. Methods and Results:, Cheeses were manufactured from raw milk artificially contaminated with S. aureus at ca 5 log CFU ml,1, a commercial starter culture and one of seven strains of BP-LAB, added as adjuncts at 0·1%. HPT of cheeses were performed on days 2 or 50 at 300 MPa (10°C, 10 min) or 500 MPa (10°C, 5 min). On day 3, S. aureus counts were 6·46 log CFU g,1 in control cheese. Milk inoculation with different BP-LAB lowered S. aureus counts on day 3 when compared with control cheese by up to 0·46 log CFU g,1, HPT at 300 MPa on day 2 by 0·45 log CFU g,1 and HPT at 500 MPa on day 2 by 2·43 log CFU g,1. Combinations of BP-LAB with HPT at 300 and 500 MPa on day 2 lowered S. aureus counts on day 3 by up to 1·02 and 4·00 log CFU g,1 respectively. Conclusions:, The combined effect of milk inoculation with some of the BP-LAB tested and HPT of cheese on S. aureus inactivation was synergistic. Significance and Impact of the Study:, The combination of HPT at lower pressures with BP-LAB inoculation is a feasible system to improve cheese safety in case of deleterious effects on cheese quality caused by HPT at higher pressures. [source] Intermittent and persistent shedding of Escherichia coli O157 in cohorts of naturally infected calvesJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2004S.E. Robinson Abstract Aims:, We conducted two short-term studies of cohorts of naturally infected calves to determine the prevalence and concentrations of Escherichia coli O157 shed in faeces. Methods and Results:, Two cohorts of calves were sampled; in the first study 14 calves were sampled up to five times a day for 5 days; in the second study a group of 16 separate calves were sampled once or twice a day for 15 days. All cattle within the two cohorts shed E. coli O157 at some point during the respective studies. In 18% of samples, E. coli O157 could only be isolated using immunomagnetic separation after an enrichment period, suggesting concentrations <250 CFU g,1. The highest concentrations recorded were 6·7 × 105 and 1·6 × 106 CFU g,1 for studies 1 and 2 respectively. Conclusions:, Persistent, high shedders (shedding >103 CFU g,1) were evident in both studies but, in the majority of calves, the pathogen was isolated intermittently. Significance and Impact of the Study:, The variable patterns of shedding have important implications for the design of appropriate sampling protocols and for gaining meaningful estimates of parameters used in mathematical models of transmission. [source] Identification of Escherichia coli O172 O-antigen gene cluster and development of a serogroup-specific PCR assayJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2004H. Guo Abstract Aim:, To characterize the locus for O-antigen biosynthesis from Escherichia coli O172 type strain and to develop a rapid, specific and sensitive PCR-based method for identification and detection of E. coli O172. Methods and Results:, DNA of O-antigen gene cluster of E. coli O172 was amplified by long-range PCR method using primers based on housekeeping genes galF and gnd Shot gun bank was constructed and high quality sequencing was performed. The putative genes for synthesis of UDP-FucNAc, O-unit flippase, O-antigen polymerase and glycosyltransferases were assigned by the homology search. The evolutionary relationship between O-antigen gene clusters of E. coli O172 and E. coli O26 is shown by sequence comparison. Genes specific to E. coli O172 strains were identified by PCR assays using primers based on genes for O-unit flippase, O-antigen polymerase and glycosyltransferases. The specificity of PCR assays was tested using all E. coli and Shigella O-antigen type strains, as well as 24 clinical E. coli isolates. The sensitivity of PCR assays was determined, and the detection limits were 1 pg ,l,1 chromosomal DNA, 0·2 CFU g,1 pork and 0·2 CFU ml,1 water. The total time required from beginning to end of the procedure was within 16 h. Conclusion:, The O-antigen gene cluster of E. coli O172 was identified and PCR assays based on O-antigen specific genes showed high specificity and sensitivity. Significance and Impact of the Study:, An O-antigen gene cluster was identified by sequencing. The specific genes were determined for E. coli O172. The sensitivity of O-antigen specific PCR assay was tested. Although Shiga toxin-producing O172 strains were not yet isolated from clinical specimens, they may emerge as pathogens. [source] Effect of inoculation dosing on the composting of source-selected organic fraction of municipal solid wastesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2006Raquel Barrena Abstract The effects of a commercial inoculum (MicroGest 10X, Brookside Agra L.C.) on the field-scale composting of the source-selected organic fraction of municipal solid wastes (OFMSW) have been studied by following routine parameters of the composting process (temperature, oxygen content and moisture) and biologically-related tests such as the respirometric index and the maturity grade. The inoculum was added to composting piles of OFMSW at different levels: control (no added inoculum), treatment A (105 CFU g,1 of OFMSW), treatment B (106 CFU g,1 of OFMSW) and treatment C (107 CFU g,1 of OFMSW). The inoculum selected produced a significant acceleration of the composting process with high levels of biological activity in the thermophilic phase. In terms of the acceleration of composting and economy the optimal treatment was B, which produced a reduction of approximately half of the total composting time. Treatment C did not improve significantly the results obtained with treatment B, whereas treatment A has little effect on the composting of OFMSW when compared with the control experiment. Respirometric index (determined at 55 °C) and maturity grade appeared to be the most reliable tests to follow the biological activity of the composting of OFMSW. On the other hand, routine parameters such as temperature, oxygen content and moisture showed no significant differences among the different inoculation levels tested in the composting process. Copyright © 2005 Society of Chemical Industry [source] Monitoring the colonization of sugarcane and rice plants by the endophytic diazotrophic bacterium Gluconacetobacter diazotrophicus marked with gfp and gusA reporter genesLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2010L.F.M. Rouws Abstract Aims:, To evaluate the colonization process of sugarcane plantlets and hydroponically grown rice seedlings by Gluconacetobacter diazotrophicus strain PAL5 marked with the gusA and gfp reporter genes. Methods and Results:, Sugarcane plantlets inoculated in vitro with PAL5 carrying the gfp::gusA plasmid pHRGFPGUS did not present green fluorescence, but ,-glucuronidase (GUS)-stained bacteria could be observed inside sugarcane roots. To complement this existing inoculation methodology for micropropagated sugarcane with a more rapid colonization assay, we employed hydroponically grown gnotobiotic rice seedlings to study PAL5,plant interaction. PAL5 could be isolated from the root surface (108 CFU g,1) and from surface-disinfected root and stem tissues (104 CFU g,1) of inoculated plants, suggesting that PAL5 colonized the internal plant tissues. Light microscopy confirmed the presence of bacteria inside the root tissue. After inoculation of rice plantlets with PAL5 marked with the gfp plasmid pHRGFPTC, bright green fluorescent bacteria could be seen colonizing the rice root surface, mainly at the sites of lateral root emergence, at root caps and on root hairs. Conclusion:, The plasmids pHRGFPGUS and pHRGFPTC are valid tools to mark PAL5 and monitor the colonization of micropropagated sugarcane and hydroponic rice seedlings. Significance and Impact of the Study:, These tools are of use to: (i) study PAL5 mutants affected in bacteria,plant interactions, (ii) monitor plant colonization in real time and (iii) distinguish PAL5 from other bacteria during the study of mixed inoculants. [source] Evaluation of PetrifilmÔ EC method for enumeration of E. coli from soilLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2010A.D. Samarajeewa Abstract Aims:, To evaluate the suitability of commercially available PetrifilmÔ EC plates for enumeration of Escherichia coli from soil. Methods and Results:, A confirmed E. coli strain isolated from liquid swine manure was inoculated into sterilized sandy clay loam and loam soils at the concentrations of 102, 103, 105 CFU g,1 of soil. The efficiency of recovery on PetrifilmÔ EC plates for soils spiked with E. coli was compared with standard membrane filtration techniques on m-FC basal medium supplemented with 3-bromo-4-chloro-5-indoyl-,- d -glucopyranoside (BCIG) and most probable numbers (MPN) techniques in E. coli medium with 4-methylumbelliferyl-,- d -glucuronide (EC-MUG) broth. PetrifilmÔ EC and m-FC (BCIG) methods were then assessed for the ability to recover E. coli from field soils applied with swine manure. No significant differences (P > 0·05) were observed between PetrifilmÔ EC, m-FC (BCIG) and MPN methods for the recovery of E. coli from spiked samples, irrespective of soil type. However, recovery of E. coli from manure-applied field soil samples showed a significant difference (P < 0·05) between the PetrifilmÔ EC method and the m-FC method in enumerating E. coli possibly as a result of false positives on m-FC. Conclusion:, The PetrifilmÔ EC method is suitable for the enumeration of E. coli from soil with a detection limit of 10 CFU g,1 soil. Significance and Impact of the Study:, The commercially available PetrifilmÔ EC method is comparatively low cost, easy to use method for the enumeration of E. coli from soil without the need for further confirmation tests. [source] Inactivation of Cronobacter spp. (Enterobacter sakazakii) in infant formula using lactic acid, copper sulfate and monolaurinLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2010M.A. Al-Holy Abstract Aims:, To investigate the effect of lactic acid (LA), copper (II), and monolaurin as natural antimicrobials against Cronobacter in infant formula. Methods and Results:, The effect of LA (0·1, 0·2 and 0·3% v/v), copper (II) (10, 50 and 100 ,g ml,1) and monolaurin (1000, 2000, and 3000 ,g ml,1) suspended into tween-80Ô or dissolved in ethanol against Cronobacter in infant formula was investigated. Reconstituted infant formula and powdered infant formula were inoculated with five strains of Cronobacter spp. at the levels of c. 1 × 106 CFU ml,1 and 1 × 103 CFU g,1, respectively. LA at 0·2% v/v had a bacteriostatic effect on Cronobacter growth, whereas 0·3% v/v LA resulted in c. 3 log10 reduction. Copper (II) at the levels of 50 ,g ml,1 and 100 ,g ml,1 elicited c. 1 and 2 log10 reductions, respectively. The combination of 0·2% LA and 50 ,g ml,1 copper (II) resulted in a complete elimination of the organism. Monolaurin exhibited a slight inhibitory activity against Cronobacter (c. 1·5 log10 difference) compared to the control when ethanol was used to deliver monolaurin. Conclusions:, A complete elimination of Cronobacter was obtained when a combination of sublethal concentrations of LA (0·2%) and copper (II) (50 ,g ml,1) was used. Significance and Impact of the Study:, The use of the synergistic interactive combination of LA and copper (II) could be beneficial to control Cronobacter in the infant formula industry. [source] Effect of selected antimicrobial compounds on the radiosensitization of Salmonella Typhi in ground beefLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2009M. Turgis Abstract Aims:, In this study, we extended our previous work to determine the efficiency of antimicrobial compounds in increase of relative radiosensitivity of Salmonella Typhi in medium fat ground beef (23% fat) by testing 41 different essential oils (EOs), oleoresins and food sauces. Methods and Results:, Ground beef samples inoculated with Salmonella Typhi (106 CFU g,1) were treated with each antimicrobial compound at a concentration of 0·5% (w/w). Then, the samples (25 g each) were packaged under air and irradiated in a 60Co irradiator at doses from 0 to 1·75 kGy. Radiosensitivity was evaluated by calculating relative radiation sensitivity, defined as the ratio of radiation D10 value in the absence/presence of antimicrobial compound. Conclusions:, Depending on the compound tested, the addition of antimicrobial compound decreased the D10 value of Salmonella Typhi, resulting in an increase of the radiation sensitivity up to more than four times. Among these antimicrobial compounds, Chinese cinnamon EO, clove EO and trans -cinnamaldehyde were most effective to increase the radiosensitivity of Salmonella Typhi in ground beef. Significance and Impact of the Study:, These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi. [source] Inactivation of Vibrio parahaemolyticus in pure culture, whole live and half shell oysters (Crassostrea virginica) by X-rayLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2009B.S.M. Mahmoud Abstract Aims:, To study the inactivation effect of different doses of X-ray on Vibrio parahaemolyticus in pure culture, inoculated whole live and half shell oysters and to evaluate the efficacy of X-ray doses on reduction of inherent microflora on oysters. Methods and Results:, X-ray was produced using RS 2400 generator system (Rad Source Technologies Inc.). Pure culture of V. parahaemolyticus, inoculated half and whole shell oysters with V. parahaemolyticus were treated with 0·0, 0·1, 0·5, 0·75, 1·0, 1·5, 2·0, 3·0 and 5·0 kGy X-ray. Surviving bacteria in the pure culture and inoculated oysters, before and after treatment, were enumerated using overlay plating (in TSA then TCBS) and most probable number (MPN) methods. A greater than 6·0 log reduction of V. parahaemolyticus was observed with 0·75, 2·0 and 5·0 kGy X-ray for pure culture, half shell and whole shell oysters, respectively. Treatment with 0·75, 2·0 and 5·0 kGy X-ray reduced the MPN to <3 for pure culture, half and whole shell oysters, respectively. Treatment with 1·0 kGy X-ray significantly (P < 0·05) reduced the inherent micro-organisms on whole shell oysters from 4·7 ± 0·1 to less than the detectable limit (<1·0 log CFU g,1). Conclusions:, X-ray (1,5 kGy) significantly (P < 0·05) reduced V. parahaemolyticus and inherent microflora on oysters to less than detectable limit (<1·0 log CFU g,1). Significance and Impact of the Study:, Treatment with X-ray could control pathogenic bacteria and extend the shelf life of oysters. [source] Detection of enterotoxigenic Staphylococcus aureus isolates in raw milk cheeseLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2007P. Cremonesi Abstract Aim:, To develop an easy, rapid and efficient DNA extraction procedure for Staphylococcus aureus detection with a low number of steps and removing completely the PCR inhibitors, applicable to raw milk cheese samples, and to compare phenotypical and genotypical method to detect Staph. aureus isolates and staphylococcal enterotoxins (SEs) production. Methods and Results:, A total of 33 bovine and caprine raw milk cheese samples were analysed by means of both classic microbiological and molecular techniques. All samples were positive for Staph. aureus contamination. The DNA extraction protocol optimized was found to achieve a detection limit of 100 CFU g,1 for Staph. aureus. None of the samples tested with immunological assays contained SEs but in 14 of 33 samples a mixture of se positive (sea, sec, sed, seg, sel, sej) isolates were identified. Conclusions:,Staphylococcus aureus is a food-borne pathogen mainly detected in finished dairy products. The rapid and efficient detection of Staph. aureus isolates from dairy products is essential for consumer safety. The direct detection of pathogens from food is possible with careful attention to sample preparation and nucleic acid amplification optimization. Significance and Impact of the Study:, This study shows that raw milk cheese samples can be tested for Staph. aureus contamination with a rapid, simple and reproducible procedure. [source] Determination of survival, identity and stress resistance of probiotic bifidobacteria in bio-yoghurtsLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2006V.S. Jayamanne Abstract Aims:, To determine the level of bifidobacteria in bio-yoghurts in the UK, identify the species, and compare the resistance of common Bifidobacterium spp. to acidity and oxidative stress. Methods and Results:, A storage trial of bio-yoghurts was carried out to determine the level and survival of bifidobacteria. The 16S rRNA gene targeted PCR was used to identify the species. Acid tolerance was determined by introducing the organisms to pH-adjusted skimmed milk and enumerating during storage at 4°C. Oxidative stress resistance was determined using the H2O2 disc diffusion assay technique. Nine of 10 bio-yoghurts contained bifidobacteria at levels >106 CFU g,1 at the time of purchase. The viability of the organism decreased during storage and on expiry only five products retained viability >106 CFU g,1 while two others were very close to the target population. Bifidobacterium animalis ssp. lactis showed superior survival abilities and stress tolerance compared with Bifidobacterium longum, Bifidobacterium breve, Bifidobacterium bifidum, Bifidobacterium adolescentis and Bifidobacterium longum biotype infantis. Conclusions:,Bifidobacterium animalis ssp. lactis, the only Bifidobacterium spp. found in bio-yoghurts, had the greatest resistance to acidity and oxidative stress. Significance and Impact of the Study:, The technological properties of B. animalis ssp. lactis make it suitable for inclusion in bio-yoghurts although its putative health benefits need further investigation. [source] Microbiological survey of prepackaged pâté and ham in New ZealandLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2005T.L. Wong Abstract Aims:, To gauge the effectiveness of pâté and ham manufacturers' management of the microbial safety and quality of their products. Methods and Results:, A survey of 60 batches of prepackaged pâté showed that 41·7% of the batches had aerobic plate counts (APC) exceeding 105 CFU g,1, one of pâté sample contained a Bacillus cereus count of >5000 CFU g,1 and another contained 1700 CFU g,1 of Listeria monocytogenes. No other pathogens were isolated from any of the samples. The survey of prepackaged ham showed that only 1% (1/104) of the ham samples were positive for L. monocytogenes (50 CFU g,1). Conclusions:, The presence of microbial hazards in these foods has generally declined since the early 1990s in New Zealand. Noncomplying APC levels may be due to an over-estimation of product shelf life or poor food handling practices during manufacture. Significance and Impact of the Study:, Few of the samples tested contained pathogens at significant levels. The prevalences of L. monocytogenes in pâté and ham were low. The presence of 1700 CFU g,1 of L. monocytogenes in a pâté sample indicates that occasionally, the population can be exposed to levels of L. monocytogenes above the zero tolerance level set in New Zealand. [source] Temporal events in the intravenous challenge model for experimental Candida albicans infections in female miceMYCOSES, Issue 3 2005Donna M. MacCallum Summary We characterized the intravenous (i.v.) challenge model for disseminated Candida albicans infection in female BALB/c and DBA/2 mice. Clearance of fungi from the bloodstream and appearance of fungi in tissues were measured at intervals after challenge with various doses of C. albicans. The wild-type isolate SC5314 and derived strains CAF2,1 and CAI-4 transformed with CIp10 were of equal virulence in the model. Variability in mouse survival times, kidney fungal burdens and cachexia was lowest when challenge inocula were within the range 104,105 CFU g,1 body weight in BALB/c mice, but brain fungal burdens and outcomes in DBA/2 mice were variable for all inocula tested. Critical times in the development of infections in optimally challenged BALB/c mice were at 5,10 h (bloodstream fully cleared of fungi), 24 h (start of exponential fungal growth in kidneys) and 48 h (50% of blood cultures become positive). Differential involvement of right and left kidneys occurred almost exclusively in mice challenged with <2 × 104 CFU g,1. We conclude that the i.v. challenge model in female BALB/c mice is now sufficiently well characterized to permit more refined experimentation in future virulence studies with C. albicans mutants. [source] | ||||||||||||||||