Reduction of Escherichia coli O157:H7 on radish seeds by sequential application of aqueous chlorine dioxide and dry‐heat treatment

Aims: To assess the effectiveness of sequential treatments of radish seeds with aqueous chlorine dioxide (ClO₂) and dry heat in reducing the number of Escherichia coli O157:H7. Methods and Results: Radish seeds containing E. coli O157:H7 at 5·5 log CFU g^?1 were treated with 500 μg ml^?1 ClO₂ for 5 min and subsequently heated at 60°C and 23% relative humidity for up to 48 h. Escherichia coli O157:H7 decreased by more than 4·8 log CFU g^?1 after 12 h dry‐heat treatment. The pathogen was inactivated after 48 h dry‐heat treatment, but the germination rate of treated seeds was substantially reduced from 91·2 ± 5·0% to 68·7 ± 12·3%. Conclusions: Escherichia coli O157:H7 on radish seeds can be effectively reduced by sequential treatments with ClO₂ and dry heat. To eliminate E. coli O157:H7 on radish seeds without decreasing the germination rate, partial drying of seeds at ambient temperature before dry‐heat treatment should be investigated, and conditions for drying and dry‐heat treatment should be optimized. Significance and Impact of the study: This study showed that sequential treatment with ClO₂ and dry‐heat was effective in inactivating large numbers of E. coli O157:H7 on radish seeds. These findings will be useful when developing sanitizing strategies for seeds without compromising germination rates.     

Evaluation of Aerated Steam Treatment of Alfalfa and Mung Bean Seeds To Eliminate High Levels of Escherichia coli O157:H7 and O178:H12, Salmonella enterica,and Listeria monocytogenes

Sprouts contaminated with human pathogens are able to cause food-borne diseases due to the favorable growth conditions for bacteria during germination and because of minimal processing steps prior to consumption. We have investigated the potential of hot humid air, i.e., aerated steam, to treat alfalfa and mung bean seeds which have been artificially contaminated with Escherichia coli O157:H7, Salmonella enterica subsp. enterica serovar Weltevreden, and Listeria monocytogenes Scott A. In addition, a recently collected E. coli O178:H12 isolate, characterized by a reduced heat sensitivity, was exposed to the treatment described. Populations of E. coli O157:H7 and S. enterica on alfalfa and mung bean seeds could be completely eliminated by a 300-s treatment with steam at 70 ± 1°C as revealed by enrichment studies. L. monocytogenes and E. coli O178:H12 could not be completely eliminated from artificially inoculated seeds. However, bacterial populations were reduced by more than 5 log CFU/g on alfalfa and by more than 4 log CFU/g on mung bean seeds. The germination rate of mung beans was not affected by the 300-s treatment compared to the germination rate of untreated seeds whereas that of alfalfa seeds was significantly lower by 11.9%. This chemical-free method is an effective alternative to the 20,000-ppm hypochlorite treatment presently recommended by the U.S. Food and Drug Administration (FDA).     

Reduction of Salmonella on alfalfa seeds using peroxyacetic acid and a commercial seed washer is as effective as treatment with 20 000 ppm of Ca(OCl)2

Aims: The efficacy of a commercial seed washer and 1 and 3% peroxyacetic acid or 20 000 ppm calcium hypochlorite for reducing Salmonella on alfalfa seeds was investigated. Methods and Results: Alfalfa seeds were inoculated with Salmonella Stanley to achieve c. 5 log CFU g^?1. Seeds were then treated with 1 or 3% peroxyacetic acid or 20 000 ppm calcium hypochlorite for 15 min in a commercial seed washer that uses air to enhance contact of the sanitizer with the seed. Experiments were also conducted using industry and laboratory methods. An c. 1‐log reduction in number of Salm. Stanley was demonstrated regardless of the chemical treatment or method of treatment. Although this 1‐log reduction was significant (P < 0·05), differences among the treatments were not significant. Treating the seed with 1 and 3% peroxyacetic acid resulted in similar Salm. Stanley reductions of 1·77 and 1·34 log, respectively, not being statistically significant (P > 0·05). Conclusions: These results suggest that under conditions tested, 1 or 3% peroxyacetic acid solutions are equally effective as 20 000 ppm of Ca(OCl)₂ in the reduction of Salm. Stanley on alfalfa seed when used in conjunction with a commercial seed washer. Significance and Impact of the Study: A 1% peroxyacetic acid solution could potentially be used in place of 20 000 ppm of Ca(OCl)₂ for treatment of seeds used for sprouting_. The commercial seed washer did not enhance removal of Salm. Stanley from alfalfa seeds, but did facilitate removal of excess soil from seeds.     

Efficacy of chlorine and heat treatment in killing Salmonella stanley inoculated onto alfalfa seeds and growth and survival of the pathogen during sprouting and storage.

The efficacy of chlorine and hot water treatments in killing Salmonella stanley inoculated onto alfalfa seeds was determined. Treatment of seeds containing 10(2) to 10(3) CFU/g in 100-micrograms/ml active chlorine solution for 5 or 10 min caused a significant (P < or = 0.05) reduction in population, and treatment in 290-micrograms/ml chlorine solution resulted in a significant reduction compared with treatment in 100 micrograms of chlorine per ml. However, concentrations of chlorine of up to 1,010 micrograms/ml failed to result in further significant reductions. Treatment of seeds containing 10(1) to 10(2) CFU of S. stanley per g for 5 min in a solution containing 2,040 micrograms of chlorine per ml reduced the population to undetectable levels (< 1 CFU/g). Treatment of seeds in water for 5 or 10 min at 54 degrees C caused a significant reduction in the S. stanley population, and treatment at > or = 57 degrees C reduced populations to < or = 1 CFU/g. However, treatment at > or = 54 degrees C for 10 min caused a substantial reduction in viability of the seeds. Treatment at 57 or 60 degrees C for 5 min appears to be effective in killing S. stanley without substantially decreasing germinability of seeds. Storage of seeds for 8 to 9 weeks at 8 and 21 degrees C resulted in reductions in populations of S. stanley of about 1 log10 and 2 log10 CFU/g, respectively. The behavior of S. stanley on seeds during soaking germination, sprouting, and refrigerated storage of sprouts was determined. An initial population of 3.29 log10 CFU/g increased slightly during 6 h of soaking, by about 10(3) CFU/g during a 24-h germination period, and by an additional 10 CFU/g during a 72-h sprouting stage. A population of 10(7) CFU/g of mature alfalfa sprouts was detected throughout a subsequent 10-day storage period at 5 degrees C. These studies indicate that while populations of S. stanley can be greatly reduced, elimination of this organism from alfalfa seeds may not be reliably achieved with traditional disinfection procedures. If S. stanley is present on seeds at the initiation of the sprout production process, populations exceeding 10(7) CFU/g can develop and survive on mature sprouts exposed to handling practices used in commercial production and marketing.     

Use of bacteriophage endolysin EL188 and outer membrane permeabilizers against Pseudomonas aeruginosa

Aims: To select and evaluate an appropriate outer membrane (OM) permeabilizer to use in combination with the highly muralytic bacteriophage endolysin EL188 to inactivate (multi‐resistant) Pseudomonas aeruginosa. Methods and Results: We tested the combination of endolysin EL188 and several OM permeabilizing compounds on three selected Ps. aeruginosa strains with varying antibiotic resistance. We analysed OM permeabilization using the hydrophobic probe N‐phenylnaphtylamine and a recombinant fusion protein of a peptidoglycan binding domain and green fluorescent protein on the one hand and cell lysis assays on the other hand. Antibacterial assays showed that incubation of 10⁶Ps. aeruginosa cells ml^?1 in presence of 10 mmol l^?1 ethylene diamine tetraacetic acid disodium salt dihydrate (EDTA) and 50 μg ml^?1 endolysin EL188 led to a strain‐dependent inactivation between 3·01 ± 0·17 and 4·27 ± 0·11 log units in 30 min. Increasing the EL188 concentration to 250 μg ml^?1 further increased the inactivation of the most antibiotic resistant strain Br667 (4·07 ± 0·09 log units). Conclusions: Ethylene diamine tetraacetic acid disodium salt dihydrate was selected as the most suitable component to combine with EL188 in order to reduce Ps. aeruginosa with up to 4 log units in a time interval of 30 min. Significance and Impact of the Study: This in vitro study demonstrates that the application range of bacteriophage encoded endolysins as ‘enzybiotics’ must not be limited to gram‐positive pathogens.     

Inactivation of plant infecting fungal and viral pathogens to achieve biological containment in drainage water using UV treatment

Aim: To explore whether ultraviolet (UV) light treatment within a closed circulating and filtered water drainage system can kill plant pathogenic species. Methods and Results: Ultraviolet experiments at 254 nm were conducted to determine the inactivation coefficients for seven plant pathogenic species. At 200 mJ cm^?2, the individual species log reductions obtained for six Ascomycete fungi and a cereal virus were as follows: Leptosphaeria maculans (9·9‐log), Leptosphaeria biglobosa (7·1‐log), Barley stripe mosaic virus (BSMV) (4·1‐log), Mycosphaerella graminicola (2·9‐log), Fusarium culmorum (1·2‐log), Fusarium graminearum (0·6‐log) and Magnaporthe oryzae (0·3‐log). Dilution experiments showed that BSMV was rendered noninfectious when diluted to >1/512. Follow‐up large‐scale experiments using up to 400 l of microbiologically contaminated waste water revealed that the filtration of drainage water followed by UV treatment could successfully be used to inactivate several plant pathogens. Conclusions: By combining sedimentation, filtration and UV irradiation within a closed system, plant pathogens can be successfully removed from collected drainage water. Significance and Impact of the Study: Ultraviolet irradiation is a relatively low cost, energy efficient and labour nonintensive method to decontaminate water arising from a suite of higher biological containment level laboratories and plant growth rooms where genetically modified and/or quarantine fungal and viral plant pathogenic organisms are being used for research purposes.     

Identification and quantification of viable Bifidobacterium breve strain Yakult in human faeces by using strain-specific primers and propidium monoazide

Aims: To develop a quick and accurate PCR‐based method to evaluate viable Bifidobacterium breve strain Yakult (BbrY) in human faeces. Methods and Results: The number of BbrY in faeces was detected by using strain‐specific quantitative real‐time PCR (qPCR) derived from a randomly amplified polymorphic DNA analysis. And using propidium monoazide (PMA) treatment, which combined a DNA‐intercalating dye for covalently linking DNA in dead cells and photoactivation, only viable BbrY in the faeces highly and significantly correlated with the number of viable BbrY added to faecal samples within the range of 10⁵–10⁹ cells per g of faeces was enumerated. After 11 healthy subjects ingested 10·7 log CFU of BbrY daily for 10 days, 6·9 (±1·5) log CFU g^?1 [mean (±SD)] of BbrY was detected in faeces by using strain‐specific transgalactosylated oligosaccharide–carbenicillin (T‐CBPC) selective agar medium. Viable BbrY detected by qPCR with PMA treatment was 7·5 (±1·0) log cells per g and the total number (viable and dead) of BbrY detected by qPCR without PMA treatment was 8·1 (±0·8) log cells per g. Conclusions: Strain‐specific qPCR with PMA treatment evaluated viable BbrY in faeces quickly and accurately. Significance and Impact of the Study: Combination of strain‐specific qPCR and PMA treatment is useful for evaluating viable probiotics and its availability in humans.     

Potted plants in hospitals as reservoirs of pathogenic fungi

The soils of five potted plants cultivated within a hospital were investigated for the presence of fungal opportunistic pathogens of humans. A total of 16 potentially pathogenic species were isolated, including Aspergillus fumigatus at up to 53.5 colony-forming units (CFU) per gram dry soil and Scedosporium apiospermum (Pseudallescheria boydii) at up to 97.0 CFU/g. Other common species included Phialophora verrucosa and Fusarium solani. Scedosporium inflatum, a recently described emerging pathogen, is reported for the first time from an environmental source. The results of this study, in combination with previous case reports linking mycoses to potted plants and available information on the establishment and dispersal of fungal opportunistic pathogens in indoor habitats, indicate that indoor plant soils constitute a serious mycotic hazard to the immunosuppressed patient.     

Use of zero-valent iron biosand filters to reduce Escherichia coli O157:H12 in irrigation water applied to spinach plants in a field setting

Aims:  Zero‐valent iron (ZVI) filters may provide an efficient method to mitigate the contamination of produce crops through irrigation water. Methods:  A field‐scale system was utilized to evaluate the effectiveness of a biosand filter (S), a biosand filter with ZVI incorporated (ZVI) and a control (C, no treatment) in decontaminating irrigation water. An inoculum of c. 8·5 log CFU 100 ml^?1 of Escherichia coli O157:H12 was introduced to all three column treatments in 20‐l doses. Filtered waters were subsequently overhead irrigated to ‘Tyee’ spinach plants. Water, spinach plant and soil samples were obtained on days 0, 1, 4, 6, 8, 10, 13 and 15 and analysed for E. coli O157:H12 populations. Results:  ZVI filters inactivated c. 6 log CFU 100 ml^?1E. coli O157:H12 during filtration on day 0, significantly (P < 0·05) more than S filter (0·49 CFU 100 ml^?1) when compared to control on day 0 (8·3 log CFU 100 ml^?1). On day 0, spinach plants irrigated with ZVI‐filtered water had significantly lower E. coli O157 counts (0·13 log CFU g^?1) than spinach irrigated with either S‐filtered (4·37 log CFU g^?1) or control (5·23 log CFU g^?1) water. Soils irrigated with ZVI‐filtered water contained E. coli O157:H12 populations below the detection limit (2 log CFU g^?1), while those irrigated with S‐filtered water (3·56 log CFU g^?1) were significantly lower than those irrigated with control (4·64 log CFU g^?1). Conclusions:  ZVI biosand filters were more effective in reducing E. coli O157:H12 populations in irrigation water than sand filters. Significance and Impact of the Study:  Zero‐valent ion treatment may be a cost‐effective mitigation step to help small farmers reduce risk of foodborne E. coli infections associated with contamination of leafy greens.     

Antibacterial activity and mechanism of essential oils in combination with medium-chain fatty acids against predominant bovine mastitis pathogens

Bovine mastitis has become a significant economic importance for the dairy industry. Concerns regarding poor milk quality and emergence of bacterial resistance have necessitated to develop an alternative therapeutic approach to antibiotics for the treatment of mastitis. Saturated medium-chain fatty acids (MCFAs) and essential oils (EOs) are known natural antimicrobials, but their combined effect has not been investigated extensively. The objective of the present investigation was to examine the bactericidal effect of various combined treatments of eight EOs and three saturated MCFAs to inactivate predominant mastitis pathogens, including Staphylococcus aureus ATCC 29213; Escherichia coli ATCC 25922; Klebsiella pneumoniae ATCC 27736 and Streptococcus agalactiae ATCC 27956. The minimum inhibitory concentration (MIC) values confirmed that all the tested pathogens were variably susceptible to both EOs and saturated MCFAs. Among essential oils, carvacrol (CAR), trans-cinnamaldehyde (TC) and thymol (TM) showed the highest inhibitory activity at concentration 0·38–1·32 mg/mL. Carvacrol exhibited effective additive antibacterial activity in combined treatment with octanoic acid (OA) in terms of its fractional inhibitory index (0·63–0·88) and time-kill effect in reducing about 6 log CFU/mL bacterial cells in less than 5 min. The effort was also made to elucidate the mechanism of antibacterial action of CAR and OA against selected mastitis pathogens by observing changes in cell microstructure, permeability and integrity of cell membrane and their membrane potential. After adding CAR and OA at MIC level, there were obvious changes in cell morphology, leakage of small electrolytes and macromolecules at the initial few hours of treatment i.e. within 1–2 h were observed. Our results indicated that CAR and OA could be evaluated as alternatives or adjuncts to antibiotics as intramammary infusion or topical application to treat bovine mastitis, significantly improving the microbiological safety of milk.     

Antimicrobial activity of lemongrass oil against Salmonella enterica on organic leafy greens

Aims: We investigated the antimicrobial effectiveness of lemongrass essential oil on organic leafy greens, romaine and iceberg lettuces and mature and baby spinach, inoculated with Salmonella Newport. The influences of exposure times and abuse temperatures on bacterial survival were also investigated. Methods and Results: Leaf samples were washed, inoculated with Salm. Newport (6‐log CFU ml^?1) and dried. Inoculated leaves were immersed in solutions containing 0·1, 0·3 or 0·5% lemongrass oil in phosphate‐buffered saline for 1 or 2 min and then individually incubated at 4 or 8°C. Samples were taken at day 0, 1 and 3 for the enumeration of survivors. Compared to the PBS control, romaine and iceberg lettuces, and mature and baby spinach samples showed between 0·6–1·5‐log, 0·5–4·3‐log, 0·5–2·5‐log and 0·5–2·2‐log CFU g^?1 reductions in Salm. Newport by day 3, respectively. Conclusions: The antimicrobial activity of lemongrass oil against Salm. Newport was concentration and time dependent. The antimicrobial activity increased with exposure time; iceberg samples treated for 2 min generally showed greater reductions (P < 0·05) than those treated for 1 min (c. 1‐log reduction difference for 0·3 and 0·5% treatments). Few samples showed a difference between refrigeration and abuse temperatures. Significance and Impact of the Study: This study demonstrates the potential of lemongrass oil solutions to inactivate Salm. Newport on organic leafy greens.     

The growth potential of Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes in dairy manure‐based compost in a greenhouse setting under different seasons

Aim: The pathogen growth in dairy compost was studied in a greenhouse setting under different seasons. Methods and Results: The five‐strain mixtures of each Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes were inoculated separately into dry compost to yield c. 1 log CFU g^?1. After acclimation at room temperature, the inoculated compost was initially adjusted to moisture levels of 10–50% and then kept in a greenhouse under different seasons. The populations of all three pathogens increased by 2·1–3·9 log CFU g^?1 within 3 days in autoclaved compost with initial moisture content of at least 40%. Listeria monocytogenes multiplied up to 2·4 log CFU g^?1 in compost with initial moisture content of 30% and was detected up to 28 days for all seasons, whereas populations of both E. coli O157:H7 and Salmonella increased by c. 1 log in compost with initial moisture content of 30% during winter months only. No pathogen growth in nonautoclaved compost was detected. Conclusion: Bacterial species, temperature, light intensity and moisture content affected the growth potential and survival of pathogens in compost when the population of background microflora was low. Significance and Impact of the Study: Keeping compost as dry as possible and maintaining certain levels of background microflora may be critical to prevent the growth of pathogens.     

Relationship between Thermal Transitions and Freezing Injury in Pea and Soybean Seeds

In an attempt to correlate freezable water with freezing injury, the thermal behavior of pea (Pisum sativum L.) and soybean (Glycine max L. Merr) seed parts at different moisture contents were compared with survival of the seeds when exposed to low temperatures. Thermal transitions between −150 and 10°C were studied using differential scanning calorimetry. In pea, reduction of germinability, after exposure of seeds to temperatures between − 18 and − 180°C, occurred at a constant moisture content (about 0.33 gram H₂O/gram dry weight) regardless of the temperature; this moisture level was above that at which freezable water was first detectable by differential scanning calorimetry (0.26 gram H₂O/gram dry weight). In contrast, damage to soybean seeds was observed at progressively lower moisture contents (from 0.33 to 0.20 gram H₂O/gram dry weight) when the temperature was decreased from −18°C to −50°C. At −18 and −30°C, moisture contents at which damage to soybean seeds was evident were above that at which freezable water was first detectable (0.23 gram H₂O/gram dry weight). However, at −50, −80, and −180°C, damage was evident even when freezable water was not detectable. The data suggest that, while the quantity of water is important in the expression of freezing injury, the presence of freezable water does not account for the damage.     

Growth of Salmonella on sprouting alfalfa seeds as affected by the inoculum size, native microbial load and Pseudomonas fluorescens 2-79

Aims: To investigate the growth of salmonellae on sprouting alfalfa seeds as affected by the inoculum size, microbial load and Pseudomonas fluorescens 2–79. Methods and Results: Alfalfa seeds pre‐inoculated with ≤10¹–10³ CFU g^?1 of salmonellae and with or without Ps. fluorescens 2–79 were sprouted in glass jars and the population of salmonellae were determined daily for up to 6 days. The population of salmonellae on germinating seeds reached the maximum 2–3 days after sprouting when total bacterial count reached the maximum (10⁹ CFU g^?1). The population of salmonellae on sprouting seeds not treated with Ps. fluorescens 2–79 showed a net increase of 3–4 log units. However, the population of salmonellae on alfalfa seeds treated with Ps. fluorescens 2–79 showed a net increase of only 1–2 log units. Disinfection of seeds with calcium hypochlorite enhanced the growth of salmonellae. Conclusions: Treatment of seeds with Ps. fluorescens 2–79 reduced the growth of salmonellae by 2–3 log units. Significance and Impact of the Study: The potential of Ps. fluorescens 2–79 as a biological agent for use in control of salmonellae on sprouting seeds was demonstrated and warrants further investigation.     

Ascomycetous yeast species recovered from grapes damaged by honeydew and sour rot

Aims: To identify ascomycetous yeasts recovered from sound and damaged grapes by the presence of honeydew or sour rot. Methods and Results: In sound grapes, the mean yeast counts ranged from 3·20 ± 1·04 log CFU g^?1 to 5·87 ± 0·64 log CFU g^?1. In honeydew grapes, the mean counts ranged from 3·88 ± 0·80 log CFU g^?1 to 6·64 ± 0·77 log CFU g^?1. In sour rot grapes counts varied between 6·34 ± 1·03 and 7·68 ± 0·38 logCFU g^?1. Hanseniaspora uvarum was the most frequent species from sound samples. In both types of damage, the most frequent species were Candida vanderwaltii, H. uvarum and Zygoascus hellenicus. The latter species was recovered in high frequency because of the utilization of the selective medium DBDM (Dekkera/Brettanomyces differential medium). The scarce isolation frequency of the wine spoilage species Zygosaccharomyces bailii (in sour rotten grapes) and Zygosaccharomyces bisporus (in honeydew affected grapes) could only be demonstrated by the use of the selective medium ZDM (Zygosaccharomyces differential medium). Conclusions: The isolation of several species only from damaged grapes indicates that damage constituted the main factor determining yeast diversity. The utilization of selective media is required for eliciting the recovery of potentially wine spoilage species. Significance and Impact of the Study: The impact of damaged grapes in the yeast ecology of grapes has been underestimated.     

Dry/wet cycling reduces spore germination and viability in six peatland bryophytes

• Dry/wet cycling driven by water level fluctuation in wetlands may strongly influence the destiny of seeds. However, how dry/wet cycling affects spore survival and germinability in peatland bryophytes is poorly understood.
• Six peatland bryophytes, three hummock- and three hollow-dwelling Sphagnum species, were chosen as study species. We tested the effects of dry (60% air RH)/wet (waterlogging) cycle frequency (once per 12, 8 or 4 days for low, medium or high, respectively) and ratio (3:1, 1:1 or 1:3 dry:wet time per cycle) on spore germinability, viability, dormancy percentage and protonema development.
• Dry/wet cycling significantly reduced spore germination percentage and viability and slowed protonema development in all Sphagnum species, being more pronounced with higher dry/wet cycling frequencies. The hummock species S. capillifolium and S. fuscum had higher spore germination percentage after the continuous dry treatment, while the hollow species S. angustifolium, S. squarrosum and S. subsecundum showed the opposite response, compared to the continuously wet treatment. Except for S. squarrosum, spore viability was higher after the dry than after the wet treatment. Spore viability and dormancy percentage were higher after a dry/wet ratio of 1:3 than after ratios of 3:1 and 1:1.
• Our study shows that both germinability and viability of bryophyte spores are reduced by dry/wet cycling (especially when frequent) in peatlands. This emphasizes the need to ensure constant water levels and low frequencies of water level fluctuation, which are relevant in connection with wetland restoration, to promote Sphagnum spore survival and establishment in peatlands after disturbances.

     

Impairment in reproductive development is a major factor limiting yield of black gram under zinc deficiency

Black gram [Vigna mungo (L.) Hepper] cv. IPU 94 plants grown in sand culture with deficient zinc (0.1 μM Zn) nutrition and those deprived of normal (1 μM) Zn supply at the initiation of flowering, showed decrease in dry matter production and especially seed yield. These plants showed a decrease in the size of anthers and stigmatic heads, pollen producing capacity of the anthers and stigmatic exudations. Zn deficiency caused structural alterations in exine and retarded germination of pollen grains and tube growth. The pollen extracts and stigmatic exudates of the Zn-deficient plants showed increase in activity of acid phosphatase isoforms and inhibition of esterase isoforms. Zn deficiency led to decrease in number of pods, seeds per pod and seed mass, altered seed coat topography and reduced seeds germinability. Low seed yield under Zn deficiency is attributed to a role of Zn in pollen function, as also in pollen-pistil interaction conducive to fertilization and development of seeds.     

Inactivation of Escherichia coli O157:H7 on radish seeds by sequential treatments with chlorine dioxide, drying, and dry heat without loss of seed viability

We developed and validated a treatment to inactivate Escherichia coli O157:H7 on radish seeds without decreasing seed viability. Treatments with aqueous ClO(2) followed by drying and dry-heat treatments were evaluated for efficacy to inactivate the pathogen. Conditions to dry radish seeds after treatment with water (control) or ClO(2) were established. When treated seeds with high water activity (a(w)) (>0.99) were stored at 45°C and 23% relative humidity (RH), the a(w) decreased to <0.30 within 24 h. Drying high-a(w) seeds before exposing them to dry-heat treatment (≥60°C) was essential to preserve seed viability. The germination rate of radish seeds which had been immersed in water for 5 min, dried at 45°C and 23% RH for 24 h, and heated at 70°C for 48 h or at 80°C for 24 h was not significantly decreased (P ≤ 0.05) compared to that of untreated radish seeds. Sequential treatments with ClO(2) (500 μg/ml, 5 min), drying (45°C, 23% RH, 24 h), and dry heating (70°C, 23% RH, 48 h) eliminated E. coli O157:H7 (5.9 log CFU/g) on radish seeds and, consequently, sprouts produced from them without decreasing the germination rate. These sequential treatments are recommended for application to radish seeds intended for sprout production.     

Fate of Escherichia coli O157:H7 in ground beef following high‐pressure processing and freezing

Aims: The purposes of this study were to evaluate the efficacy of high pressure to inactivate Escherichia coli O157:H7 in ground beef at ambient and subzero treatment temperatures and to study the fate of surviving bacteria postprocess and during frozen storage. Methods and Results: Fresh ground beef was inoculated with a five‐strain cocktail of E. coli O157:H7 vacuum‐packaged, pressure‐treated at 400 MPa for 10 min at ?5 or 20°C and stored at ?20 or 4°C for 5–30 days. A 3‐log CFU g^?1 reduction of E. coli O157:H7 in the initial inoculum of 1 × 10⁶ CFU g^?1 was observed immediately after pressure treatment at 20°C. During frozen storage, levels of E. coli O157:H7 declined to <1 × 10² CFU g^?1 after 5 days. The physiological status of the surviving E. coli was affected by high pressure, sensitizing the cells to pH levels 3 and 4, bile salts at 5% and 10% and mild cooking temperatures of 55–65°C. Conclusions: High‐pressure processing (HPP) reduced E. coli O157:H7 in ground beef by 3 log CFU g^?1 and caused substantial sublethal injury resulting in further log reductions of bacteria during frozen storage. Significance and Impact of the Study: HPP treatment of packaged ground beef has potential in the meat industry for postprocess control of pathogens such as E. coli O157:H7 with enhanced safety of the product.     

Culture conditions influencing phytase production of Mitsuokella jalaludinii,a new bacterial species from the rumen of cattle

AIMS: To determine the effectiveness of combined treatments with chemicals, heat and ultrasound in killing or removing Salmonella and Escherichia coli O157:H7 on alfalfa seeds intended for sprout production. METHODS AND RESULTS: Alfalfa seeds inoculated with Salmonella or E. coli O157:H7 were treated with ultrasound (38.5-40.5 kHz) in solutions containing 1% Ca(OH)(2), 1% Tween 80, 1% Ca(OH)(2) plus 1% Tween 80, 160 microg ml(-1) Tsunami 200 and 0.5% Fit at 23 and 55 degrees C for 2 and 5 min. Highest reductions were in chemical solutions at 55 degrees C, but seed viability was also reduced compared with treatment at 23 degrees C. Inactivation of Salmonella and E. coli O157:H7 was generally enhanced by simultaneous treatments with ultrasound, chemicals and heat. CONCLUSIONS: Ultrasound treatment, in combination with chemicals and heat, had a modest enhancing effect on the effectiveness of chemicals in killing or removing pathogens on alfalfa seeds. Overall, treatment with 1% Ca(OH)(2) was most effective in killing Salmonella and E. coli O157:H7. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of 1% Ca(OH)(2) instead of 20,000 microg ml(-1) chlorine, which is currently recommended as a sanitizer for seeds intended for sprout production in the US, should be considered. Ultrasound treatment of alfalfa seeds containing Salmonella or E. coli O157:H7, in combination with chemical treatment, contributes to achieving greater reductions in populations of these pathogens, thereby reducing the risk of contamination and the presence of pathogens in sprouts produced from these seeds.