Decontamination of chicken carcasses artificially contaminated with Salmonella

A study was conducted to evaluate the efficacy of three chemical disinfectants and of ionising radiation in reducing the level of contamination in chicken carcasses which had been artificially contaminated with Salmonella Virchow. Chicken carcasses were obtained from a local abattoir. Five carcasses and one control carcass were used to test each concentration of disinfectant and the radiation. The amount of contaminant employed was 0.5 ml of 10(4) colony-forming units per ml of S. Virchow spread over the thigh, breast and wing areas. All treatments were conducted in duplicate. The three disinfectants used were as follows: calcium hypochlorite, at concentrations of 20 ppm, 50 ppm, 100 ppm and 200 ppm of available chlorine. Lactic acid at concentrations of 0.5%, 0.75% and 1%. Hydrogen peroxide compound at concentrations of 1%, 2% and 3%. Five inoculated carcasses were immersed at a time in one disinfectant concentration for 15 min, while the control carcasses were simultaneously immersed in water free from disinfectants. Five carcasses, each in a plastic bag, were subjected to varying ascending doses (from 2 to 7 k gray [kGy]) of ionising radiation from radioactive isotopes of cobalt 60. A bacteriological examination of each carcass was conducted after the treatment to determine the presence or absence of S. Virchow. The number of carcasses which gave positive results showing the presence of Salmonella decreased after chemical treatment, but the organism was not completely eliminated. However, in those carcasses subjected to 7 kGy of radiation, Salmonella was eliminated and no changes in the appearance, colour or smell of the carcasses were observed.     

Efficacy of spray application of chlorinated water in killing pathogenic bacteria on raw apples, tomatoes, and lettuce

Washing whole and cut produce by dipping or submerging in chlorinated water has a sanitizing effect, although reduction in microbial populations is minimal and is usually less than 100-fold. A study was undertaken to evaluate the efficacy of a spray application of chlorine in killing Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, yeasts and molds, and total aerobic mesophilic microorganisms on whole apples, tomatoes, and lettuce leaves. Inoculated produce was treated (sprayed and then soaked) with water (control) or solutions containing 200 or 2,000 ppm of chlorine for 0, 1, 3, 5, or 10 min, rinsed with sterile water, and analyzed for populations (CFU/cm2) of target microorganisms. Compared to the control treatment, further reductions in numbers of pathogens of 0.35 to 2.30 log CFU/cm2 were achieved by treatment with chlorine. Chlorine was generally more effective at 2,000 ppm than at 200 ppm. Inactivation of microorganisms occurred essentially within 1 min after application of chlorine. These reductions are significant relative to populations of pathogenic microorganisms that may be present on produce. Spray application of chlorine to raw produce at food service or household levels may be a suitable, and more convenient, alternative to treatment by dipping or submersion.     

Involvement of calcium in ACC-oxidase activity from Cicer arietinum seed embryonic axes

Both in vivo and in vitro ACC-oxidase activities as well as ethylene production from embryonic axes of chickpea seeds were strongly inhibited by EGTA, a selective extracellular Ca2+ ion chelator, indicating that the influx of Ca2+ is important for enzymatic activity. EGTA inhibition was restored by exogenous Ca2+. Treatments of embryonic axes with either Verapamil and LaCl3 (both Ca2+ channel blockers) or TMB-8 (an intracellular Ca2+ antagonist) provoked an inhibition of both ACC-oxidase activity and ethylene production. These results suggest an involvement of calcium fluxes and intracellular calcium levels in the activity of the last step of the ethylene biosynthetic pathway, which is, in turn, intimately correlated with germination of Cicer arietinum seeds.     

Epilepsy associated with low-grade brain glial neoplasms

Ozone and chlorine are agents that disinfect by destroying, neutralizing or inhibiting the growth of pathogenic microorganisms. The treatment of drinking water with ozone has shown to be more efficient against spores of Bacillus subtilis. It was observed that the ozone already in dose of 0.35 mg/l produced the reduction of at least 5 log in populations of approximately 1 x 10(6) cells/ml of Escherichia coli, Vibrio cholerae, Salmonella typhi, Yersinia enterocolitica, Pseudomonas aeruginosa, Aeromonas hydrophila, Listeria monocytogenes and Staphylococcus aureus. With a dose of 0.50 mg/l of chlorine, the reduction was much smaller for the tested microorganisms (except Vibrio cholerae), while the effect of 2 mg/l of chlorine was similar to the ozone treatment. For spores of Bacillus subtilis, the reduction observed with ozone concentrations of 0.35 and 0.70 mg/l was of almost 3 log, while no considerable effect was obtained with chlorine in the tested conditions. Our results have shown that both disinfectans were consumed during the treatment period, probably because of the own water demand and the added bacterial mass.     

Hodgkin''s disease occurring in a child after liver transplantation

Broiler chicks were treated by oral gavage on the day of hatch with a continuous-flow competitive exclusion culture (PREEMPT). At 4 h, 1 day, or 2 days posttreatment, chicks were challenged by oral gavage with 10(2) or 10(4) Salmonella CFU to determine the effects of challenge time on Salmonella cecal colonization. Cecal propionic acid concentrations in two trials increased (P < or = 0.001) within 1 day posttreatment in chicks given PREEMPT, and the increases were indicative of the establishment of the PREEMPT bacteria. Salmonella cecal populations decreased (P < or = 0.001) on average 6 log10 units in these two trials in chicks challenged 4 h posttreatment with 10(4) Salmonella CFU. In a third trial propionic acid did not increase significantly until 2 days after treatment, and there was no decrease in Salmonella colonization when chicks were challenged at 4 h after treatment. However, there were decreases in that same trial when chicks were challenged at 1 and 2 days after treatment. The early establishment of PREEMPT followed by challenges with 10(2) and 10(4) Salmonella CFU resulted in 3% and 3%, respectively, of the ceca testing Salmonella-culture-positive, compared to 28% and 95%, respectively, culture-positive ceca in untreated chicks. The results from this study indicated that in most instances young broiler chicks can be protected against cecal colonization when challenged with 10(2) and 10(4) Salmonella CFU as early as 4 h posttreatment on the day of hatch with the PREEMPT bacteria.     

Effect of truncated projections on defect detection in attenuation-compensated fanbeam cardiac SPECT

Na-nitrilotriacetic acid (Na3NTA) and Fe-nitrilotriacetic acid (FeNTA) have both been described to cause tumors in the urinary tract of rodents. However, these effects were observed using different modes of administration at extremely different dose levels and explained by different mechanisms. Whereas FeNTA causes an iron overload of cells and is genotoxic in various assays, Na3NTA is predominantly bound to zinc in vivo and thereby causes cytotoxic effects in the urinary tract. In contrast to FeNTA, Na3NTA requires high dose levels to produce tumors. The aim of this study was to compare the effects of Na3NTA and FeNTA on cellular proliferation, histopathology, lipid peroxidation, and 8-OH-2'-deoxyguanosine levels in the kidneys as well as on the urinary excretion of Ca, Fe, and Zn. For evaluation of DNA synthesis both compounds were administered for 1 or 4 weeks to 14-week-old male Wistar rats at a tumor causing dose, Na3NTA via the diet at 150 ppm and 20,000 ppm (approximately 9 and approximately 1000 mg/kg/day) and FeNTA i.p. at 25 mg/kg/day. An osmotic minipump, containing 20 mg/ml BrdU, was implanted subcutaneously 7 days before necropsy. Na3NTA showed nearly no effect on DNA replication after 1 week but a strong reaction after 4 weeks. The increase was 10- to 18-fold in different renal compartments. The enhancement of proliferation in the proximal tubules was nearly twice that in the distal tubules. In contrast, FeNTA caused DNA replication during the first week, and this was restricted to the proximal tubules. After 4 weeks there was an 18-fold increase in the outer stripe and no effect in the inner stripe of the outer medulla. The data presented give evidence to the assumption that both substances increase cell proliferation as a compensatory mechanism, causing different pattern of tubular proliferation in terms of time course and affected cell types. Both Na3NTA at 20,000 ppm and FeNTA led to increased lipid peroxidation, whereas increased levels of 8-OH-2'-deoxyguanosine were observed only after treatment with FeNTA. Urinary excretion of Zn was increased 30-fold after administration of 20,000 ppm Na3NTA but only 2-fold after administration of FeNTA. Urinary excretion of Ca and Fe remained unchanged after treatment with either Na3NTA and FeNTA. These results show that the Na3NTA-related proliferative effects are not mediated by an internal formation of FeNTA.     

Relative effectiveness of selenite cystine broth, tetrathionate broth, and rappaport-vassiliadis medium for recovery of Salmonella spp. from raw flesh, highly contaminated foods, and poultry feed: collaborative study

A collaborative study was performed in 18 laboratories to validate use of Rappaport-Vassiliadis (RV) medium in the standard culture method for recovery of Salmonella spp. from raw, highly contaminated foods and poultry feed. RV medium made from its individual ingredients and incubated at 42 degrees C was compared with selenite cystine (SC) broth incubated at 35 degrees C and tetrathionate (TT) broth incubated at 35 degrees and 43 degrees C for effectiveness in recovery of Salmonella spp. Four artificially contaminated foods (oysters, frog legs, mushrooms, and shrimp) and poultry feed and one naturally contaminated food (chicken) were analyzed. The artificially contaminated foods were inoculated with single serovars of Salmonella at target levels of 0.04 colony-forming units (CFU)/g for the low level and 0.4 CFU/g for the high level. For analysis of 1125 test portions, RV medium (42 degrees C) recovered Salmonella from 409 test portions; TT (43 degrees C), from 368 test portions; TT (35 degrees C), from 310 test portions; and SC (35 degrees C), from 334 test portions. Overall, RV medium was comparable with or better than other selective enrichments for recovery of Salmonella from the foods in this study, except mushrooms. From mushrooms, SC broth (35 degrees C) recovered more positive test portions than did RV medium (42 degrees C) and TT broth (43 degrees C). The method for detection of Salmonella in raw, highly contaminated foods and poultry feed using RV medium has been adopted by AOAC INTERNATIONAL. AOAC Official Method 967.25, Salmonella in Foods, Preparation of Culture Media and Reagents, has been revised to include RV medium, and the applicability of AOAC Official Method 967.26, Salmonella in Foods, Detection, has been restricted to processed foods.     

Effect of resistance exercise training on cortical and cancellous bone in mature male rats

The thermal inactivation kinetics of Salmonella enteritidis PT4 between 49 and 60 degrees C were investigated. Using procedures designed to eliminate methodological artifacts, we found that the death kinetics deviated from the accepted model of first-order inactivation. When we used high-density stationary-phase populations and sensitive enumeration, the survivor curves at 60 degrees C were reproducibly biphasic. The decimal reduction time at 60 degrees C (D60 degrees C) of the tail subpopulation was more than four times that of the majority population. This difference decreased with decreasing temperature; i.e., the survivor curves became more linear, but the proportion of tail cells remained a constant proportion of the initial population, about 1 in 10(4) to 10(5). Z plots (log D versus temperature) for the two populations showed that the D values coincided at 51 degrees C, indicating that the survivor curves should be linear at this temperature, and this was confirmed experimentally. Investigations into the nature of the tails ruled out genotypic differences between the populations and protection due to leakage from early heat casualties. Heating of cells at 59 degrees C in the presence of 5 or 100 micrograms of chloramphenicol per ml resulted in reductions in the levels of tailing. These reductions were greatest at the higher chloramphenicol concentration. Our results indicate that de novo protein synthesis of heat shock proteins is responsible for the observed tailing. Chemostat-cultured cells heated at 60 degrees C also produced biphasic survivor curves in all but one instance. Cells with higher growth rates were more heat sensitive, but tailing was comparable with batch cultures. Starved cells (no dilution input) displayed linear inactivation kinetics, suggesting that during starvation a rapid heat shock response cannot be initiated.     

Biochemical changes in Pinus pinea seeds. III. The effect of growth substances and steroidal hormones on nucleic acids

The effects of exogenous growth factors (indolacetic acid, gibberellic acid and kinetin and steroidal hormones (estrone, estradiol and testosterone on the germination pattern of Pinus pinea seeds were studied. Nucleic acids metabolism during the stages before germination, has also been investigated. Seeds sown in the presence of all these substances, showed a higher growth rate and a higher germination degree than their respective controls; kinetin and estradiol were the most active factors. The level of total nucleic acids was studied in seeds after one day soaking and on the 1rst, 3rd, 5th, and 7th day after sowing. Megagametophytes contained a higher amount of acids when growth factors and steroidal hormones were present, specially after one day soaking. In embryos; after the 3rd day, a similar result was obtained. The RNA fraction increased the most.     

Selenium-mediated differential response of beta-glucosidase and beta-galactosidase of germinating Trigonella foenum-graecum

Beta-glucosidase and beta-galactosidase activity profile tested in different seeds during 24 h germination revealed reasonably high levels of activity in Vigna radiata, Cicer arietinum, and Trigonella foenum-graecum. In all seeds tested, beta-galactosidase activity was, in general, higher than that of beta-glucosidase. T. foenum-graecum seedlings exhibited maximal total and specific activities for both the enzymes during 72 h germination. Se supplementation as Na2SeO3 up to 0.75 ppm was found to be beneficial to growth and revealed selective enhancement of beta-galactosidase activity by 40% at 0.5 ppm Se. The activities of both the enzymes drastically decreased at 1.0 ppm level of Se supplementation. On the contrary, addition of Na2SeO3 in vitro up to 1 ppm to the enzyme extracts did not influence these activities. Hydrolytic rates of beta-glucosidase in both control and Se-supplemented groups were enhanced by 20% with 0.05 M glycerol in the medium and 30% at 0.1 M glycerol. The rates were marginally higher in Se-supplemented seedlings than the controls, irrespective of added glycerol in the medium. In contrast, hydrolysis by beta-galactosidase showed a trend of decrease in Se-supplemented seedlings compared to the control, when glycerol was present in the medium. Addition of Se in vitro in the assay medium showed no difference in the hydrolytic rate by beta-galactosidase when compared to control, while the activity of beta-glucosidase declined by 50%. Se-grown seedlings showed an enhancement of transglucosidation rate by 40% in the presence of 0.1 M glycerol. The study reveals a differential response to Se among the beta-galactosidase and beta-glucosidase of T. foenum-graecum with increase in the levels of beta-galactosidase activity.     

Expression of the smooth-muscle proteins alpha-smooth-muscle actin and calponin, and of the intermediate filament protein desmin are parameters of cardiomyocyte maturation in the prenatal rat heart

Tip growth of plant cells has been suggested to be regulated by a tip-focused gradient in cytosolic calcium concentration ([Ca2+]c). However, whether this gradient orients apical growth or follows the driving force for this process remains unknown. Using localized photoactivation of the caged calcium ionophore Br-A23187 we have been able to artificially generate an asymmetrical calcium influx across the root hair tip. This led to a change in the direction of tip growth towards the high point of the new [Ca2+]c gradient. Such reorientation of growth was transient and there was a return to the original direction within 15 min. Root hairs forced to change the direction of their growth by placing a mechanical obstacle in their path stopped, reoriented growth to the side, and grew past the mechanical blockage. However, as soon as the growing tip had cleared the obstacle, growth returned to the original direction. Confocal ratio imaging revealed that a tip-focused [Ca2+]c gradient was always centered at the site of active growth. When the root hair changed direction the gradient also reoriented, and when growth returned to the original direction, so did the [Ca2+]c gradient. This normal direction of apical growth of Arabidopsis thaliana (L.) Heynh, root hairs was found to be at a fixed angle from the root of 85 +/- 6.7 degrees. In contrast, Tradescantia virginiana (L.) pollen tubes that were induced to reorient by touch or localized activation of the caged ionophore, did not return to the original growth direction, but continued to elongate in their new orientation. These results suggest that the tip-focused [Ca2+]c gradient is an important factor in localizing growth of the elongating root hair and pollen tube to the apex. However, it is not the primary determinant of the direction of elongation in root hairs, suggesting that other information from the root is acting to continuously reset the growth direction away from the root surface.     

L-374,087, an efficacious, orally bioavailable, pyridinone acetamide thrombin inhibitor

The potential for transfer of Escherichia coli O157:H7 from contaminated ground beef to grinding equipment and the inactivation of attached cells during cleaning and sanitizing was examined. Chub-packed ground beef with lean:fat ratios of 75:25, 80:20 or 90:10 was inoculated with 6 log CFU/g or 2 log CFU/g E. coli O157:H7 strain FRIK 910. Samples were consecutively ground in a Hobart meat grinder with stainless steel (SS) chips (1 cm2) glued to the auger housing. Chips were harvested after grinding, detergent washing with or without manual scrubbing and rinsing, sanitizing in a chlorine or peroxyacetic acid sanitizer, and overnight storage. Survival of E. coli O157:H7 was evaluated both by plate count and enrichment in trypticase soy broth. Approximately 3 to 4 log CFU/cm2 were attached to the SS after grinding with all three fat contents. After washing and sanitizing in a chlorine or peroxyacetic acid sanitizer, viable bacteria were infrequently recovered by plate count. Enrichment of chips resulted in a higher survival rate with both sanitizing treatments, indicating that cell numbers below the limit of detection (5 CFU/cm2) or potentially injured organisms remained on the surface. Manual scrubbing during the washing step reduced the recovery rate. The scrubbing step also increased the number of passing scores assigned using an ATP bioluminescence assay of total residual soil on the chips sanitized in chlorine. The overall results indicate that plate counts alone may not be a reliable indicator of sanitation efficacy and may be validated by enrichment assay.     

Development of antibiotic-resistant strains for the enumeration of foodborne pathogenic bacteria in stored foods

Strains of Aeromonas spp., Salmonella enteritidis phage type 4, Salmonella typhimurium, verotoxigenic Escherichia coli O157:H7 (VTEC) and Yersinia enterocolitica resistant to streptomycin, nalidixic acid and a combination of both antibiotics were selected. When compared with the parent strains, most of the antibiotic-resistant strains had slightly slower growth rates at their optimum incubation temperature but the difference was reduced progressively when the temperature was lowered. Some antibiotic-resistant strains had considerably slower growth rates in the presence of the relevant antibiotic and these were not used further. Several agar and impedance media with added streptomycin and nalidixic acid were assessed for the enumeration of the antibiotic-resistant strains in artificially contaminated stored foods. Differential/selective media were required to enumerate low numbers of antibiotic-resistant strains in certain foods. The following agar and impedance media were selected: Aeromonas Agar (Ryan) for Aeromonas spp., Xylose Lysine Agar and Lysine Iron Cysteine Neutral Red Medium for Salmonella, Eosin Methylene Blue Agar and Coliform Medium for VTEC, and Yersinia Selective Agar without selective agents for Yersinia enterocolitica. The agar and impedance media have been used successfully to enumerate antibiotic-resistant strains inoculated into foods and stored at different temperatures.     

Inclusion control of ferritic stainless steel by aluminum deoxidation and calcium treatment

A thermodynamic equilibrium between aluminum and oxygen and inclusion morphology in the Fe-16Cr stainless steel were investigated to understand the fundamentals of the aluminum deoxidation technology for ferritic stainless steels. Further, the effect of calcium addition on the changes in chemistry and morphology of inclusions was discussed. The measured results for the aluminum-oxygen equilibria exhibit relatively good agreement with the calculated values, indicating that an introduction of the first-and second-order interaction parameters, recently reported, is reasonable to numerically express the aluminum deoxidation equilibrium in a ferritic stainless steel. In the composition of dissolved aluminum content greater than about 60 ppm, pure alumina particles were observed, while the alumino-manganese silicates containing Cr₂O₃ appeared at less than 20 mass ppm of dissolved aluminum. The formation of calcium aluminate inclusions after Ca treatment can be discussed based on the thermodynamic equilibria among calcium, aluminum, and oxygen in the steel melt. In the composition of steel melt with relatively high content of calcium and low aluminum, the log ( ) of inclusions linearly increases by increasing the log [a _Ca/a _Al ² ·a _O ² ] with the slope close to unity. However, the slope of the line is significantly lower than the expected value in the composition of steel melt with relatively low calcium and high aluminum contents.     

Effect of anionic salts in prepartum diets based on alfalfa

This study compared prepartum diets based on grass, alfalfa, or alfalfa and anionic salts to investigate their effect on Ca metabolism, acid-base status, endocrine response, disease incidence, and lactational performance of periparturient dairy cows. Forty-five nonlactating Holstein cows in their last 3 wk of gestation were fed a control diet based on grass hay with a dietary cation-anion difference [expressed as milli-equivalents of ((Na + K) - (Cl + S))/100 g of dietary dry matter] of +30 or diets based on alfalfa with a dietary cation-anion difference of either +35 or -7. Cows fed the diet with the dietary cation-anion difference of -7 had the lowest urine pH prepartum and had the highest concentrations of ionized Ca in blood and total Ca in serum at parturition. Increases in 1,25-(OH)2 vitamin D per unit decrease in total Ca in serum were greatest for cows fed the diet with a dietary cation-anion difference of -7. Also, cows fed this same diet consumed the most dry matter postpartum. Incidences of health disorders were 13% (10 of 75), 12% (9 of 75), and 5% (4 of 75) for cows fed the diets with dietary cation-anion differences of +30, +35, and -7, respectively. Results indicate that alfalfa, when supplemented with anionic salts, is a viable forage for prepartum dairy cows.     

The importance of the stomach in mediating histamine-induced hypocalcemia in the rat

The effect of histamine on serum calcium homeostasis was studied in the rat. After the intravenous administration of 0.5-1.0 mg histamine base to fasted Holtzman rats weighing 80-100 g, a significant lowering of serum calcium (Ca) level occurred 30 min after injection (decrease in Ca, 1.4-1.9 mg/100 ml), but normocalcemia returned at 60 min. Repeat intravenous injections of histamine 1.0 mg resulted in repeated lowering of the serum Ca level. Hypophosphatemia did not accompany the hypocalcemia. Thyroparathyroidectomy (TPTX) did not eliminate the calcium-lowering effect of histamine in acute TPTX animals but did so in more chronic TPTX animals in which the mean serum Ca was 7.6 mg/100 ml or less. Gastrectomy, however, completely eliminated the calcium-lowering effect of histamine given in doses of up to 2 mg/rat (20 mg/kg of body weight), despite the presence of an intact thyroid gland. These studies support the role of a gastric factor and not the thyroid secretion of calcitonin in mediating this response in the rat.     

Retrograde migration of ureteral calculi

Aspergillus parasiticus NRRL-2999 was inoculated into meat mixtures with curing salts and into yeast extractsucrose (YES) and sucrose-ammonium salts (SAS) broth with and without curing salts to determine if the presence of curing salts significantly affected growth and aflatoxin production by the mold. The effect of individual curing salts or curing salt mixtures on growth and toxin elaboration by the aspergillus was substrate dependent. When YES broth contained 100 ppm of NaNO2, 2% NaCl, or 1 or 2% NaCl plus 200 ppm of NaNO2 or 200 ppm of NaNO3, growth and/or aflatoxin production was depressed. Biosynthesis of aflatoxin B1 was enhanced by presence of 1 and 4% NaCl in YES broth. The SAS broth containing only NaCl or NaCl combined with nitrite or nitrate yielded less aflatoxin than did control broth or no aflatoxin at all. When compared to the control, an increase in growth and amount of aflatoxin occurred in SAS broth which contained 200 ppm of NaNO3. Sausages containing 100 and 200 ppm NaNO2 and no NaCl supported more mold growth and aflatoxin production than did control sausage with 3% NaCl and 100 ppm of NaNO2. Addition of 2 and 3% NaCl and no nitrite to sausage resulted in less aflatoxin than in control sausage.     

Transient expression of beta-galactosidase in differentiating sporozoites of Eimeria tenella

A cocktail of seven Listeria monocytogenes isolates of food, human and environmental origin was used to assess the antilisterial activity of the bacteriocins nisin and ALTA 2341 in combination with various atmospheres: air, 100% N2, 40% CO2:60% N2, or 100% CO2. Buffered tryptone soya broth (pH 6.0) was used as the growth medium and incubation was at 4 degrees C (21 days) or 12 degrees C (7 days), or when temperature fluctuated between these values for defined periods. It was observed that atmosphere alone influenced the growth rate of L. monocytogenes, with 100% CO2 exerting the greatest inhibition. A 5 log population increase was observed in all atmospheres after 7 days at 12 degrees C. At 4 degrees C a 4-5 log population increase was observed in air, 100% N2 and 40% CO2:60% N2 within 21 days. Growth was prevented by 100% CO2. In the presence of nisin (400 IU/ml), an increase in the lag phase was observed before growth (5 log population increase after 7 days) in all atmospheres at 12 degrees C. This effect was enhanced at 4 degrees C where a maximum 2 log population increase was observed in all atmospheres except 100% CO2, in which growth was prevented. Increasing the concentration of nisin to 1250 IU/ml prevented L. monocytogenes growth in all atmosphere combinations at 4 and 12 degrees C. Two concentrations of ALTA 2341 were also tested. In the presence of 0.1% ALTA 2341 and at 12 degrees C, a 3-5 log population increase was observed in all atmospheres with the exception of 100% CO2, which prevented L. monocytogenes growth. At 4 degrees C, growth was observed in the combination of 0.1% ALTA 2341 and 100% N2 only (3 log population increase). Use of a higher concentration of ALTA 2341 (1.0%) resulted in a population decrease below the detection level within 24 h in all atmosphere/temperature combinations. Re-growth occurred in the presence of 1.0% ALTA 2341 in all atmospheres at 12 degrees C, and in combination with air or 100% N2 at 4 C. When the effectiveness of either nisin or ALTA 2341 and atmosphere was tested against L. monocytogenes as temperature fluctuated for periods between 4 and 12 degrees C, only the combination of 100% CO2 and 1.0% ALTA 2341 prevented growth. Cells surviving exposure to nisin or ALTA 2341 were recovered from 28 of the 32 combinations tested that contained bacteriocin. Nisin survivors remained sensitive to the bacteriocin. ALTA 2341 survivors had become resistant to the bacteriocin.     

Low calcium diet and 1,25-dihydroxyvitamin D(3) infusion modulate immune responses during Mycobacterium paratuberculosis infection in beige mice

A 12-month study was conducted to evaluate the effects of feeding a low calcium (Ca) diet or 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3) infusion on the persistence of Mycobacterium paratuberculosis infection using a mouse model. Male beige mice 6-8 weeks of age were assigned to one of the following treatments: (1) non-infected, (2) infected,(3) non-infected/1,25(OH)(2)D(3), (4) infected/1,25(OH)(2)D(3), and (5) infected/low Ca (0.15 percent) diet. Infected mice were inoculated intravenously with live M. paratuberculosis. At 1, 6 and 12 months postinfection, mice in Treatments 3 and 4 were implanted subcutaneously with mini-osmotic pumps to deliver 1,25(OH)(2)D(3). Infusion with 1,25(OH)(2)D(3) exacerbated M. paratuberculosis infection in most tissues at all time points. Mice infused with 1,25(OH)(2)D(3) had higher bacterial counts in spleen, liver, and ileum compared with control infected mice after 1 month of infection. In contrast, feeding a low Ca diet reduced the number of viable organisms cultured from the liver and ileum of infected mice. Plasma Ca and 1,25(OH)(2)D(3) were increased in mice infused with 1,25(OH)(2)D(3) at all time points but values for low Ca mice were not different than for non-infused mice. Splenocyte production of TNF, IL-1 and IL-6 was higher for mice fed the low Ca diet compared with control infected mice after 1 month of infection. Inducible IL-6 activity remained higher for this treatment at 6 months postinfection. These results suggest that feeding a low Ca diet to mice chronically infected with M. paratuberculosis appears to enhance their ability to clear the infection in a manner distinct from any effect of 1,25(OH)2D3.