Thermal Inactivation of Borrelia burgdorferi, the Cause of Lyme Disease

1990 ◽  
Vol 53 (4) ◽  
pp. 296-299 ◽  
Author(s):  
SI K. LEE ◽  
AHMED E. YOUSEF ◽  
ELMER H. MARTH
Keyword(s):  
Borrelia Burgdorferi ◽  
Thermal Inactivation ◽  
Treatment Time ◽  
Treatment Temperature ◽  
Most Probable Number ◽  
Lag Phase ◽  
Probable Number ◽  
Heat Treated ◽  
Thermal Death ◽  
D Values

Borrelia burgdorferi strain EBNI was cultivated in BSK-II medium at 34°C, then cultures at different physiological states were heat-treated at temperatures in the range of 50 to 70°C. Numbers of survivors were estimated by the Most Probable Number technique. Log MPN was plotted against treatment time, and resulting survivor curves were linear. Estimated D-values for cultures incubated at 34°C for 7 d before heat-treatment were 5.5, 4.3, 2.7, .47, and .14 min at 50, 55, 60, 65, and 70°C, respectively. Spirochetes in the lag phase had greater resistance to heat than those in the stationary phase, with the latter being more resistant to heat than spirochetes in the same phase of growth but refrigerated at 4°C for 3 d. D-values for B. burgdorferi are generally less at 50°C, and greater at 70°C than those reported for other nonsporeforming pathogens. When log10 MPN was plotted against treatment temperature, two linear segments for each thermal death curve were obtained. Our data show the spirochete had higher z-values than most nonsporeforming pathogens. The pH of the medium, in the range of 5.0 to 7.6, did not affect resistance of B. burgdorferi to heat.

Survival of Borrelia burgdorferi in Whole Milk, Low Fat Milk, and Skim Milk at 34°C and in Skim Milk at 5°C

1991 ◽  
Vol 54 (7) ◽  
pp. 532-536 ◽  
Author(s):  
GERALDINE M. FARRELL ◽  
AHMED E. YOUSEF ◽  
ELMER H. MARTH
Keyword(s):  
Borrelia Burgdorferi ◽  
Milk Protein ◽  
Skim Milk ◽  
Storage Period ◽  
Most Probable Number ◽  
Low Fat ◽  
Probable Number ◽  
Whole Milk ◽  
The Mean ◽  
D Values

Autoclaved whole milk, low-fat milk, protein-fortified skim milk and regular skim milk were inoculated to contain ca. 105 to 106 Borrelia burgdorferi strains 35210, 35211, or EBNI/ml and stored at 34°C for 16 d. Similarly inoculated skim milk also was held at 5°C for 46 d. Numbers of survivors were estimated by the Most Probable Number (MPN) technique. In all instances, numbers of B. burgdorferi decreased over the storage period. At 34°C, no strain of B. burgdorferi was detected after day 12. The mean D-values, at 34°C, for strains 35210, 35211, and EBNI were 2.2, 2.4, and 2.2 d, respectively. The mean D-values, at 34°C, for all strains in whole milk, low-fat milk, protein-fortified skim milk, and regular skim milk were 2.4, 2.3, 1.9, and 2.4 d, respectively. At 5°C, spirochete numbers in regular skim milk decreased, but all three strains remained at a detectable level for 46 d. The mean D-values, at 5°C, for strains 35210, 35211, and EBNI were 12, 15, and 12 d, respectively.

Low Temperature Growth and Thermal Inactivation of Listeria monocytogenes in Precooked Crawfish Tail Meat1

1993 ◽  
Vol 56 (2) ◽  
pp. 106-109 ◽  
Author(s):  
WARREN J. DORSA ◽  
DOUGLAS L. MARSHALL ◽  
MICHAEL W. MOODY ◽  
CAMERON R. HACKNEY
Keyword(s):  
Listeria Monocytogenes ◽  
Storage Time ◽  
Thermal Inactivation ◽  
Growth Curves ◽  
Lag Phase ◽  
Short Term ◽  
Temperature Growth ◽  
Generation Times ◽  
Thermal Death ◽  
D Values

Growth of Listeria monocytogenes in precooked crawfish tail meat at 0, 6, and 12°C was determined. Thermal death times were also determined. Growth curves for L. monocytogenes revealed that little multiplication was observable for the entire storage time of 20 d at 0°C. At 6 and 12°C, exponential growth began immediately with no observed lag phase. Generation times of 72.2, 17.0, and 6.9 h were calculated at 0, 6, and 12°C, respectively. Observed D values at 55, 60, and 65°C were 10.23, 1.98, and 0.19 min, respectively. The z value for L. monocytogenes in precooked crawfish tail meat was calculated to be 5.5°C. Results from this study indicate that a refrigeration temperature of 6°C (42.8°F) will support growth of L. monocytogenes and short-term temperature abuse at 12°C will induce very rapid growth of the organism on crawfish tail meat. Thermal treatment values from this study can be used to establish postpicking heat treatments that would eliminate L. monocytogenes from packaged crawfish tail meat prior to retail sale.

Use of a Mutant Strain for Evaluating Processing Strategies to Inactivate Vibrio vulnificus in Oysters

1999 ◽  
Vol 62 (6) ◽  
pp. 592-600 ◽  
Author(s):  
CAROL S. DOMBROSKI ◽  
LEE-ANN JAYKUS ◽  
DAVID P. GREEN ◽  
BRIAN E. FARKAS
Keyword(s):  
Thermal Inactivation ◽  
Vibrio Vulnificus ◽  
Disease Risk ◽  
Capillary Tube ◽  
Control Strategies ◽  
Most Probable Number ◽  
Probable Number ◽  
Pure Cultures ◽  
Selective Plating ◽  
D Values

Vibrio vulnificus is a ubiquitous marine bacterium frequently isolated from shellfish and associated with severe and often fatal disease in humans. Various control strategies to reduce the disease risk associated with V. vulnificus contamination in shellfish have been proposed. However, evaluating the efficacy of these control strategies is complicated because of the difficulty in distinguishing V. vulnificus from the high levels of background environmental Vibrio spp. The purpose of this research was to develop a model indicator V. vulnificus strain that could be readily differentiated from background microflora and used to facilitate the evaluation of processing efficacy. A spontaneous nalidixic acid–resistant strain of V. vulnificus (Vv-NA) was prepared from a wild-type parent (Vv-WT) using selective plating techniques. Vv-NA was very similar to Vv-WT with respect to biochemical characteristics, appearance on selective plating media, detection limits using most probable number and polymerase chain reaction, and growth rate. In comparative freeze inactivation studies on pure cultures, Vv-WT and Vv-NA had similar freeze inactivation profiles at −20°C (conventional freezing), at −85°C (cold blast freezing), and in liquid nitrogen (cryogenic freezing). In oyster homogenates artificially inoculated with Vv-NA, the organism was inactivated 95 to 99% after freezing, irrespective of freezing temperature. Thermal inactivation comparisons of pure cultures of Vv-WT and Vv-NA using the capillary tube method revealed statistically significant differences in D values at 47°C (2.2 versus 3.0 min, respectively) and 50°C (0.83 versus 0.56 min, respectively), but nearly identical values at 52°C (0.21 versus 0.22 min, respectively). However, these D values were notably higher than those reported by other investigators and hence provided a conservative means by which to evaluate thermal inactivation. In oyster homogenates seeded with Vv-NA, D values of 1.3 ± 0.09 min and 0.41 ± 0.01 min were obtained at 46°C and 48°C, respectively. This study demonstrated that Vv-NA is readily enumerated and could be used as a surrogate for evaluating the degree of V. vulnificus inactivation provided by freezing and thermal treatments of oyster homogenates.

Differential Survival of Generic E. coli and Listeria spp. in Northeastern U.S. Soils Amended with Dairy Manure Compost, Poultry Litter Compost, and Heat-Treated Poultry Pellets and Fate in Raw Edible Radish Crops

2021 ◽  
Author(s):  
Marie Limoges ◽  
Deborah A. Neher ◽  
Thomas R. Weicht ◽  
Patricia D. Millner ◽  
Manan Sharma ◽  
...  
Keyword(s):  
Fresh Produce ◽  
Poultry Litter ◽  
Dairy Manure ◽  
Animal Origin ◽  
Most Probable Number ◽  
Post Inoculation ◽  
Probable Number ◽  
E Coli ◽  
Manure Compost ◽  
Heat Treated

Composted or heat-treated Biological Soil Amendments of Animal Origin (BSAAO) can be added to soils to provide nutrients for fresh produce. These products lower the risk of pathogen contamination of fresh produce when compared with use of untreated BSAAO; however, meteorological conditions, geographic location, and soil properties can influence the presence of pathogenic bacteria, or their indicators (e.g., generic E. coli) and allow potential for produce contamination. Replicated field plots of loamy or sandy soils were tilled and amended with dairy manure compost (DMC), poultry litter compost (PLC), or no compost (NoC) over two different field seasons, and non-composted heat-treated poultry pellets (HTPP) during the second field season. Plots were inoculated with a three-strain cocktail of rifampicin-resistant E. coli (rE.coli) at levels of 8.7 log CFU/m2. Direct plating and most probable number (MPN) methods measured the persistence of rE.coli and Listeria spp. in plots through 104 days post-inoculation. Greater survival of rE. coli was observed in PLC plots in comparison to DMC plots and NoC plots during year 1 (P < 0.05). Similar trends were observed for year 2, where rE. coli survival was also greater in HTPP amended plots (P < 0.05). Survival of rE. coli was dependent on soil type, where water potential and temperature were significant covariables. Listeria spp. were found in NoC plots, but not in plots amended with HTPP, PLC or DMC. Radish data demonstrate that PLC treatment promoted the greatest level of rE.coli translocation when compared to DMC and NoC treatments (P  < 0.05). These results are consistent with findings from studies conducted in other regions of the US and informs Northeast produce growers that composted and non-composted poultry-based BSAAO supports greater survival of rE. coli in field soils. This result has the potential to impact the food safety risk of edible produce grown in BSAAO amended soils as a result of pathogen contamination.

Effect of Heat Treatment on the Reactivity and Crystallinity of Coal-Char

2005 ◽  
Author(s):  
Shouyu Zhang ◽  
Junfu Lu ◽  
Jianmin Zhang ◽  
Qing Liu ◽  
Guangxi Yue
Keyword(s):  
Heat Treatment ◽  
Heat Treatment Temperature ◽  
Treatment Time ◽  
Treatment Temperature ◽  
Coal Char ◽  
Heat Treatment Time ◽  
Heat Treat ◽  
Heat Treated ◽  
Layer Stacking ◽  
Crystalline Growth

The effect of heat treatment on the reactivity and crystallinity of char prepared from the vitrinite of two coals (YX, JJ) was investigated by using XRD and TGA in this paper. The results from TGA show that the reactivity of the chars from YXV and JJV decreases with the increase of heat treatment temperature. The reactivity of YXV char decreases quickly and significantly as heat treatment time increases. However, after heat treatment time of 60 min, it decreases slowly. The effect of heat treatment time on the reactivity of JJV char is small. The results from XRD show that the crystallinity of coal-char is determined by the intensity of heat treatment. When heat treatment time is more than 60 minutes, the turbostratic crystallite of YXV char prepared under 900°C changes remarkably and becomes more orderly. The aromatic layer stacking heights (Lc) of YXV Char when heat treated above 900°C increased with the increase of heat treatment time. The effect of heat treat time on Lc of JJV char is small, but under heat treatment temperature of 1200°C, the crystalline of JJV char grows distinctly. There is a good parallel relationship between the crystalline growth and deactivation of the chars. It can be concluded that the growth of the crystalline is the main reason for the deactivation of coal-char.

scholarly journals Assessment of Watercare Efficacy on Treatment of Water for Human Consumption in Makurdi Metropolis Nigeria

2019 ◽  
Vol 1 ◽  
pp. 1-8
Author(s):  
E M Mbaawuaga ◽  
W C Agber ◽  
M W Kar
Keyword(s):  
Water Samples ◽  
Treatment Time ◽  
Water Sources ◽  
Most Probable Number ◽  
Future Research ◽  
Human Consumption ◽  
Time Interval ◽  
Probable Number ◽  
Treated Water ◽  
Significant Difference

Assessment of the efficacy of Water-Care in the treatment of water to safe health level was carried out on water samples from different water sources within six populated communities of Makurdi Metropolis. Thirty six (36) water samples were collected and treated with WaterCare based on the product manufacturer’s instructions. Treated water stored for 30 minutes and 24 hours were tested for coliforms using Multiple Tube Fermentation technique. Analysis of variance (ANOVA) was used with the Tukey Honestly Significant Difference (HSD) for multiple comparisons of the data variables. Most probable Number (MPN) of coliforms /100mL of sampled water ranged from 43 to >1,100cfu/100ml. Mean MPN of treated water for30 minutes and 24 hours interval was 37.7±33.0cfu/100ml and 16.17±14.8cfu/100ml respectively. Improved/deep sources such as boreholes show 3cfu/100ml and 0cfu/100ml respectively for 30 minutes and 24 hours treatment while unimproved/shallow sources such as wells show ≤120 cfu/100ml and ≤53 cfu/100ml respectively for 30 minutes and 24 hour interval. A significant difference between treated samples and the untreated was observed (F = 6.321, P = 0.005). Tukey multiple comparison test revealed that MPN index/100ml in the water samples was significantly lower (P =0.015, P =0.009) after treating for 30 minutes and 24 hour time interval respectively as compared to untreated water. But there was no significant difference between the 30 minute and 24 hour time interval (P =0.970). The study found that, drinking water sources in Makurdi Township were heavily contaminated, and that 30 minutes and 24 hours’ time interval was not a sufficient time for total elimination of bacteria contaminants after treatment with WaterCare. Future research should ascertain the actual treatment time for inactivation of all bacteria in water treated with WaterCare.

Alicyclobacillus in Orange Juice: Occurrence and Heat Resistance of Spores

1999 ◽  
Vol 62 (8) ◽  
pp. 883-886 ◽  
Author(s):  
MIRTHA NELLY UBOLDI EIROA ◽  
VALÉRIA CHRISTINA AMSTALDEN JUNQUEIRA ◽  
FLÁVIO L. SCHMIDT
Keyword(s):  
Heat Resistance ◽  
Orange Juice ◽  
High Heat ◽  
Heat Treatments ◽  
Most Probable Number ◽  
Biochemical Tests ◽  
Probable Number ◽  
Death Time ◽  
Spore Activation ◽  
D Values

Spore suspensions of a pure culture of Alicyclobacillus acidoterrestris DSM 2498 were submitted to different heat treatments (60°C for 60 min, 60°C for 30 min, 70°C for 20 min, 80°C for 5 min, 80°C for 10 min, 80°C for 30 min, and boiling for 5 min) to determine the best activation conditions in orange juice. The best treatment for spore activation was shown to be 70°C/20 min. Seventy-five samples of concentrated orange juice from 11 different suppliers were examined for the presence of thermophilic acid-tolerant spore formers by the most probable number technique using Bacillus acidocaldarius medium (BAM broth) and incubation at 44°C for 5 days after a prior spore activation. After incubation, isolation was carried out using BAM agar medium incubating at 44°C for 5 days. Typical colonies were submitted to a microscopic examination, evaluation for the presence of spores, and various biochemical tests. Of the orange juice samples examined, 14.7% were found to be positive for Alicyclobacillus. The thermal death time open tube method was used to determine the heat resistance of the spores of strains confirmed as being Alicyclobacillus. The D-values determined were in the range from 60.8 to 94.5 min at 85°C, 10.0 to 20.6 min at 90°C, and 2.5 to 8.7 min at 95°C. The z-values were between 7.2°C and 11.3°C. The results demonstrated the occurrence of Alicyclobacillus in orange juice and the high heat resistance of the spores that could survive the heat treatments normally applied in the processing of orange juice.

Thermal Inactivation of Escherichia coli O157:H7 Isolated from Ground Beef and Bovine Feces, and Suitability of Media for Enumeration

1998 ◽  
Vol 61 (3) ◽  
pp. 285-289 ◽  
Author(s):  
M. ROCELLE S. CLAVERO ◽  
LARRY R. BEUCHAT ◽  
MICHAEL P. DOYLE
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Treatment Temperature ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Polyethylene Bags ◽  
D Values ◽  
Bovine Feces

Rates of thermal inactivation of five strains of Escherichia coli O157:H7 isolated from ground beef implicated in outbreaks of hemorrhagic colitis and five strains isolated from bovine feces were determined. Ground beef (22% fat, 10 g), inoculated with individual test strains at populations ranging from 6.85 to 7.40 log10 CFU g−1 of beef, was formed into patties (0.3 cm thick and 8.0 cm in diameter) and sealed in polyethylene bags. For each strain and treatment temperature (54.4, 58.9, 62.8, 65.6, or 68.3°C), 6 bags were simultaneously immersed into a recirculating water bath. Viable cells in patties heated for various lengths of time were enumerated by plating diluted samples on sorbitol MacConkey agar supplemented with 4-methylumbelliferyl-β-d-glucuronide (MSMA) and modified eosin methylene blue (MEMB) agar. Regardless of strain or treatment temperature, higher numbers of E. coli O157:H7 cells were generally recovered on MEMB agar than on MSMA, indicating the inferiority of MSMA as a recovery medium for quantitative determination of E. coli O157:H7 cells in heat-processed ground beef. Significantly (P ≤ 0.05) higher D values when enumeration was done using MEMB agar compared with MSMA. Mean D values for combined strain data at 54.4, 58.9, 62.8, and 65.6°C from cultures on MEMB agar were 123.90, 6.47, 0.62, and 0.20 min, respectively, whereas D values of 25.5, 5.21, 0.57, and 0.18 min were obtained at the same temperatures from cultures on MSMA. Results suggest that cooking ground beef patties to an internal temperature of 68.3°C for 40 s will inactivate at least 99.99% of E. coli O157:H7 cells; z values of 4.0 and 5.1°C were calculated from mean D values obtained from MEMB agar and MSMA, respectively, as recovery media. Differences in D values and z values existed among strains but rates of thermal inactivation do not appear to be correlated with the sources of the isolates.

Electrical resistivity, magnetoresistance, and morphology of vapor-grown carbon fibers prepared in a mixture of benzene and Linz–Donawitz converter gas by floating catalyst method

1993 ◽  
Vol 8 (8) ◽  
pp. 1866-1874 ◽  
Author(s):  
Munehiro Ishioka ◽  
Toshihiko Okada ◽  
Kenji Matsubara ◽  
Michio Inagaki ◽  
Yoshihiro Hishiyama
Keyword(s):  
Heat Treatment ◽  
Electrical Resistivity ◽  
Carbon Fibers ◽  
Treatment Time ◽  
Liquid Nitrogen Temperature ◽  
Treatment Temperature ◽  
Heat Treated ◽  
Cobalt Acetylacetonate ◽  
Converter Gas ◽  
Transition Heat

Vapor-grown carbon fibers (VGCF's) were prepared in a mixture of benzene and Linz–Donawitz converter gas using floating catalytic seeds derived from ferrocene, cobalt acetylacetonate, and thiophene. The diameters of the fibers thus grown were in the range of 2–7 μm. The fibers were heat-treated in argon atmosphere at temperatures between 1700 and 3000 °C. The electrical resistivity at room temperature and magnetoresistance at liquid nitrogen temperature were measured for the as-grown and heat-treated fibers, and morphology of the heat-treated fibers was observed with a scanning electron microscope. The electrical resistivity was nearly similar to that obtained for VGCF's prepared on a substrate in a mixture of benzene and hydrogen. The size effects on the resistivity and magnetoresistance were observed. The magnetoresistance was also found to depend on the heat-treatment time. The magnetoresistance results showed that a transition heat-treatment temperature for the magnetoresistance change from negative to positive was between 2200 and 2300 °C, indicating the graphitizable nature of the present fiber. A characteristic polygonal appearance was observed for the fibers heat-treated above 2500 °C.

Thermal Inactivation of Listeria innocua in Salmon (Oncorhynchus keta) Caviar Using Conventional Glass and Novel Aluminum Thermal-Death-Time Tubes

2004 ◽  
Vol 67 (2) ◽  
pp. 383-386 ◽  
Author(s):  
M. AL-HOLY ◽  
Z. QUINDE ◽  
D. GUAN ◽  
J. TANG ◽  
B. RASCO
Keyword(s):  
Precise Measurement ◽  
Thermal Inactivation ◽  
Listeria Innocua ◽  
Oncorhynchus Keta ◽  
Solid Foods ◽  
Death Time ◽  
Thermal Death ◽  
Glass Tubes ◽  
D Values ◽  
Thermal Death Time

Differences in the come-up times and thermal inactivation parameters of Listeria innocua in salmon ( Oncorhynchus keta) caviar containing 2.5% salt using conventional thermal-death-time (TDT) glass tubes and a novel aluminum tube were tested and compared. Generally, the come-up times and decimal reduction times (D-values) were shorter and the change in temperature required to change the D-value (z-value) was longer in the aluminum than in the glass tubes. The D-values at 60, 63, and 65°C for the aluminum TDT tubes were 2.97, 0.77, and 0.40 min, respectively, and for the glass TDT tubes, these values were 3.55, 0.84, and 0.41 min. The z-values were 5.7°C in the aluminum and 5.3°C in the glass. Because of the shorter come-up time, the aluminum TDT tubes may provide a more precise measurement of microbial thermal inactivation than the glass TDT tubes, particularly for viscous materials, solid foods, and foods containing particulate matter.

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