Effect of Prior Growth Conditions on the Thermal Inactivation of 13 Strains of Listeria monocytogenes in Two Heating Menstrua

2005 ◽  
Vol 68 (1) ◽  
pp. 168-172 ◽  
Author(s):  
SHARON G. EDELSON-MAMMEL ◽  
RICHARD C. WHITING ◽  
SAM W. JOSEPH ◽  
ROBERT L. BUCHANAN
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Stationary Phase ◽  
Thermal Tolerance ◽  
Thermal Inactivation ◽  
Brain Heart Infusion ◽  
Acid Resistance ◽  
Growth Conditions ◽  
Ph Values ◽  
Ph Dependent

The thermal tolerance of 13 Listeria monocytogenes strains was tested using a submerged heating coil apparatus. The strains were grown individually for 18 h at 37°C in acidogenic tryptic soy broth (without dextrose) supplemented with 1% glucose and 1% glutamine (TSB+G) or nonacidogenic tryptic soy broth supplemented with 1% glutamine but containing no glucose (dextrose) (TSB−G). The former medium results in cells induced for pH-dependent, stationary-phase acid resistance, whereas the latter medium allows L. monocytogenes to grow to high numbers in the absence of glucose, yielding cells that are not induced for pH-dependent, stationary-phase acid resistance. The average final pH values of the 18-h TSB+G and the TSB−G cultures were 4.7 and 6.7, respectively. The cells grown in the acid resistance–inducing and non–acid resistance–inducing media were then tested in two heating menstrua that consisted of brain heart infusion broth adjusted to pH 3.0 and water activity (aw) of 0.987 or pH 7.0 and aw 0.970. In 14 of the 26 menstruum-strain combinations tested, the acid resistance–induced strains were more heat resistant then the equivalent noninduced cultures. No difference in the pattern of thermal resistance in response to induction of acid resistance was apparent among the different serovars tested. The results suggest that the ability of prior induction of acid resistance to enhance thermal resistance can vary substantially among L. monocytogenes strains.

Effects of pH and Acid Resistance on the Radiation Resistance of Enterohemorrhagic Escherichia coli

1999 ◽  
Vol 62 (3) ◽  
pp. 219-228 ◽  
Author(s):  
ROBERT L. BUCHANAN ◽  
SHARON G. EDELSON ◽  
GLENN BOYD
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Radiation Resistance ◽  
Brain Heart Infusion ◽  
Acid Resistance ◽  
Enterohemorrhagic Escherichia Coli ◽  
E Coli ◽  
Effects Of Ph ◽  
Ph Dependent ◽  
Subsequent Storage

The effects of pH and the induction of pH-dependent stationary-phase acid resistance on the radiation resistance of Escherichia coli were determined for seven enterohemorrhagic strains and one nonenterohemorrhagic strain. The isolates were grown in acidogenic or nonacidogenic media to pH levels of approximately 4.7 and 7.2, respectively. The cells were then transferred to brain heart infusion (BHI) broth adjusted to pH 4.0, 4.5, 5.0, and 5.5 (with HCl) that was preequilibrated to 2°C, and cultures were then irradiated using a 137Cs source. Surviving cells and the extent of injury were determined by plating on BHI and MacConkey agars both immediately after irradiation and after subsequent storage at 2°C for 7 days. Decreasing the pH of the BHI in which E. coli was irradiated had relatively little effect on the microorganism's radiation resistance. Substantial differences in radiation resistance were noted among strains, and induction of acid resistance consistently increased radiation resistance. Comparison of E. coli levels immediately after irradiation and after 7 days of refrigerated storage suggested that irradiation enhanced pH-mediated inactivation of the pathogen. These results demonstrate that prior growth under conditions that induce a pH-dependent stationary phase cross-protects E. coli against radiation inactivation and must be taken into account when determining the microorganism's irradiation D value.

Thermal Inactivation, Growth, and Survival Studies of Listeria monocytogenes Strains Belonging to Three Distinct Genotypic Lineages

2003 ◽  
Vol 66 (9) ◽  
pp. 1611-1617 ◽  
Author(s):  
ANTONIO J. DE JESÚS ◽  
RICHARD C. WHITING
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Inactivation ◽  
Brain Heart Infusion ◽  
Growth Conditions ◽  
Heat Inactivation ◽  
Survival Times ◽  
Growth And Survival ◽  
Coefficients Of Variation ◽  
Survival Studies ◽  
D Values

Twenty-one Listeria monocytogenes strains belonging to three different genotypic lineages were evaluated for differences between lineages and between individual strains with respect to thermal inactivation, growth, and survival. Three sets of heat inactivation conditions (60°C, pH 6.0, and 0.5 M lactate; 55°C, pH 6.0, and 0.5 M lactate; and 50°C, pH 4.0, and 0.5 M lactate) were used on strains grown in modified brain heart infusion (BHI) broth with and without glucose. Two sets of growth conditions (35°C, pH 6.5, and 0.1 M lactate and 5°C, pH 6.5, and 0.1 M lactate) were used with modified BHI broths to determine lag phases and exponential growth rates. Two sets of conditions (28°C, pH 4.0, and 1 M lactate and 28°C, pH 4.5, and 0.5 M lactate) were used with modified BHI broth to determine survival times (D-values). Thermal inactivation D-values were consistently lowest for lineage III, but differences were not significant for any set of conditions tested. Some significant differences were observed between lineages with respect to some of the growth and survival conditions tested. Extensive strain-to-strain variation was observed for all parameters tested. Average coefficients of variation for the thermal inactivation, growth, and survival studies were 0.31, 0.18, and 0.26, respectively. Strain-to-strain variations were approximately equal to the uncertainties associated with the analytical procedures. The results obtained indicate a diversity among strains encountered in food processing that must be accounted for in process calculations and risk assessments.

scholarly journals Aside Adapte ve Adapte Olmayan Durağan Faz Escherichia coli O157:H7, Salmonella enterica Typhimurium ve Listeria monocytogenes’in Nar Suyundaki Termal Direnci

2019 ◽  
Vol 7 (7) ◽  
pp. 1000
Author(s):  
Zeynal Topalcengiz ◽  
Sefa Işık ◽  
Yusuf Alan
Keyword(s):  
Escherichia Coli ◽  
Thermal Resistance ◽  
Stationary Phase ◽  
Salmonella Enterica ◽  
Thermal Tolerance ◽  
Thermal Inactivation ◽  
Pomegranate Juice ◽  
Escherichia Coli O157 ◽  
Acid Adaptation ◽  
E Coli

The purpose of this study was to investigate the thermal resistance of acid adapted and non-adapted stationary phase Escherichia coli O157:H7, Salmonella enterica Typhimurium and Listeria monocytogenes in pomegranate juice. In addition, the performance of generic E. coli was evaluated as an indicator. Non-adapted stationary phase cells were grown by incubating inoculated tryptic soy broth without glucose (TSB-NG) at 36±1°C for 18±2 hours. Tryptic soy broth with 1% glucose (10 g/l; TSBG) was used for acid adaptation. All media used for L. monocytogenes was supplemented with 0.6% yeast extract. After washing the cells with peptone, 5 ml of pasteurized pomegranate juice was added onto the pellet to obtain inoculated juice with a initial concentration of 107-1010 log CFU/ml. Inoculated pomegranate juice was sealed into the microcapillary tubes. Microtubes were heat treated in waterbaths at 50, 52 and 54±1°C by immersing at pre-determined time intervals. Survived populations were counted on tryptic soy agar (TSA). S. Typhimurium had the lowest thermal resistance in pomegranate juice. At 50°C, E. coli O157:H7 was the most resistant, whereas L. monocytogenes was more thermally tolerant at 52 and 54°C. Acid adaptation decreased the thermal resistance of E. coli O157:H7, but increased the heat resistance of L. monocytogenes at all tested temperatures significantly. Thermal tolerance of S. Typhimurium increased only at 50°C. The most resistant microorganism was non-adapted generic E. coli at 50 and 52°C; acid-adapted L. monocytogenes had the most thermal tolerance at 54°C. Thermal inactivation of microorganisms in pomegranate juice could be tested at lower temperatures compare to other fruit juices. This may be due to the natural antimicrobial effect and more acidic content of pomegranate juice.

scholarly journals Changes in Membrane Fatty Acid Composition ofPediococcus sp. Strain NRRL B-2354 in Response to Growth Conditions and Its Effect on Thermal Resistance

1999 ◽  
Vol 65 (7) ◽  
pp. 2857-2862 ◽  
Author(s):  
Bassam A. Annous ◽  
Michael F. Kozempel ◽  
Michael J. Kurantz
Keyword(s):  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Thermal Resistance ◽  
Stationary Phase ◽  
Acid Composition ◽  
Thermal Inactivation ◽  
Growth Conditions ◽  
Exponential Phase ◽  
Membrane Fatty Acid ◽  
Membrane Fatty Acid Composition

ABSTRACT Membrane fatty acid composition and thermal resistance (D value) of Pediococcus sp. were determined for mid-exponential-phase (ME) and stationary-phase (ST) cells grown in tryptic soy broth (TSB) and tryptone-glucose-yeast extract (TGY) at 28 and 37°C. As the cells entered the stationary phase of growth, the unsaturated fatty acid, C18:1 n11c, produced during the exponential phase of growth was converted to its cyclic form, C19:0 Δ9c. This shift in membrane fatty acid composition was accompanied by an increase in the D values of this bacterium. Data from this study suggest that the membrane fatty acid composition of Pediococcus sp. is dependent on the growth conditions and that membrane fatty acid composition plays a critical role in thermal resistance. Thermal inactivation curves ofPediococcus sp. cells grown in TGY at 28°C indicated the presence of a cell population that is heterogeneous in thermal resistance. The growth of this bacterium in TGY at 37°C and in TSB at 28 and 37°C resulted in cell populations that were uniform in thermal resistance with a lag time for thermal inactivation. Thermal inactivation curves of ME and ST cultures were similar. The data presented here suggest that the cell population’s uniformity of thermal inactivation is independent of the growth phase of the culture.

Synergistic Effects of Butyl Para-Hydroxybenzoate and Mild Heating on Foodborne Pathogenic Bacteria

2020 ◽  
Author(s):  
Zhujun Gao ◽  
Qiao Ding ◽  
Chongtao Ge ◽  
Robert C. Baker ◽  
Rohan V. Tikekar ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Pathogenic Bacteria ◽  
Thermal Inactivation ◽  
Heating Temperature ◽  
Synergistic Effects ◽  
Brain Heart Infusion ◽  
Similar Treatment ◽  
Log Reduction ◽  
Synergistic Enhancement ◽  
Foodborne Pathogenic Bacteria

ABSTRACT While high temperature heat treatments can efficiently reduce pathogen levels, they also affect the quality and nutritional profile of foods, as well as increase the cost of processing. The food additive butyl para-hydroxybenzoate (BPB) was investigated for its potential to synergistically enhance the thermal inactivation at mild heating temperatures (54 – 58 ºC). Four foodborne pathogenic bacteria, Cronobacter sakazakii , Salmonella enterica serotype Typhimurium, attenuated Escherichia coli O157:H7 and Listeria monocytogenes, were cultured to early stationary phase and then subjected to mild heating in a model food matrix (Brain Heart Infusion) containing low levels BPB (≤ 125 ppm). The heating temperature used with each bacterium was selected based on the temperature that would yield an approximate 1 – 2 log reduction over 15 min heating in BHI without BPB using a submerged coil apparatus. The inclusion of BPB at concentrations ≤ 125 ppm resulted in significant enhancement of thermal inactivation, achieving 5 – > 6 log reductions of the Gram-negative strains and D-values of < 100 sec. Listeria monocytogenes achieved at 3 – 4 log reduction with a similar treatment. No significant inactivation was noted in the absence of the mild heating for the same time period. This study provides an additional proof of concept that low temperature inactivation of foodborne pathogens can be realized by synergistic enhancement of thermal inactivation by food components that affect microbial cell membranes.

Inactivation of Escherichia coli O157:H7 in Apple Juice by Irradiation

1998 ◽  
Vol 64 (11) ◽  
pp. 4533-4535 ◽  
Author(s):  
R. L. Buchanan ◽  
S. G. Edelson ◽  
K. Snipes ◽  
G. Boyd
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Radiation Resistance ◽  
Apple Juice ◽  
Suspended Solids ◽  
Acid Resistance ◽  
E Coli ◽  
Cesium 137 ◽  
Microbiological Criteria ◽  
Ph Dependent

ABSTRACT Three strains (932, Ent-C9490, and SEA13B88) of Escherichia coli O157:H7 were used to determine the effectiveness of low-dose gamma irradiation for eliminating E. coli O157:H7 from apple juice or cider and to characterize the effect of inducing pH-dependent, stationary-phase acid resistance on radiation resistance. The strains were grown in tryptic soy broth with or without 1% dextrose for 18 h to produce cells that were or were not induced to pH-dependent stationary-phase acid resistance. The bacteria were then transferred to clarified apple juice and irradiated at 2°C with a cesium-137 irradiator. Non-acid-adapted cells had radiationD values (radiation doses needed to decrease a microbial population by 90%) ranging from 0.12 to 0.21 kGy. D values increased to 0.22 to 0.31 kGy for acid-adapted cells. When acid-adapted SEA13B88 cells were tested in five apple juice brands having different levels of suspended solids (absorbances ranging from 0.04 to 2.01 at 550 nm), radiation resistance increased with increasing levels of suspended solids, with D values ranging from 0.26 to 0.35 kGy. Based on these results, a dose of 1.8 kGy should be sufficient to achieve the 5D inactivation of E. colirecommended by the National Advisory Committee for Microbiological Criteria for Foods.

Induced Acid-Tolerance Response Confers Limited Nisin Resistance on Listeria monocytogenes Scott A

1996 ◽  
Vol 59 (9) ◽  
pp. 1003-1006 ◽  
Author(s):  
AMECHI OKEREKE ◽  
STERLING S. THOMPSON
Keyword(s):  
Listeria Monocytogenes ◽  
Acid Stress ◽  
Brain Heart Infusion ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Cross Protection ◽  
C Cells ◽  
Acid Tolerance Response ◽  
Tolerance Response ◽  
Resistance Trait

The presence of an inducible acid-tolerance response (ATR) in Listeria monocytogenes Scott A was established. Protection of cells with induced ATR against nisin-mediated inhibition and stress was also evaluated. ATR was induced in L. monocytogenes Scott A by culturing in brain heart infusion (BHI) broth buffered to pH 5.4. The unadapted cells were grown at pH 7.2. Both acid-adapted and unadapted cells were challenged at pH 3.3 and 4.3 at 35°C. The acid-adapted cells were 150- to 7,500-fold more resistant to acid stress at pH 3.3 than unadapted cells. Both cells were equally resistant to acid stress at pH 4.3. The acid-adapted and unadapted cells were exposed to 0, 0.3, 0.6, 1.2 and 1.5 μg of nisin per ml of buffered BHI broth at pH 6.0 for 90 min at 35°C. Cells with the induced acid-resistance trait were slightly more resistant to nisin than the unadapted cells. In the presence of 1.5 μg of nisin per ml, 47% of the acid-adapted cells survived compared to 41% of the unadapted cells. In the range of nisin concentration included in this study, there was no significant (P < 0.05) difference in the nisin resistance of adapted and unadapted cells. The data suggest that ATR induction confers very limited cross protection against nisin stress and kill.

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