Effect of pH-dependent, stationary phase acid resistance on the thermal tolerance of Escherichia coli O157:H7

1999 ◽  
Vol 16 (5) ◽  
pp. 447-458 ◽  
Author(s):  
R.L Buchanan ◽  
S.G Edelson
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Thermal Tolerance ◽  
Acid Resistance ◽  
Escherichia Coli O157 ◽  
Effect Of Ph ◽  
Ph Dependent

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.

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.

pH-Dependent Stationary-Phase Acid Resistance Response of Enterohemorrhagic Escherichia coli in the Presence of Various Acidulants†

1999 ◽  
Vol 62 (3) ◽  
pp. 211-218 ◽  
Author(s):  
ROBERT L. BUCHANAN ◽  
SHARON G. EDELSON
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Stress Responses ◽  
Physiological Stress ◽  
Accurate Determination ◽  
Acid Resistance ◽  
Enterohemorrhagic Escherichia Coli ◽  
Resistance Response ◽  
E Coli ◽  
Ph Dependent

The effect of acidulant identity on the pH-dependent stationary-phase acid resistance response of enterohemorrhagic Escherichia coli was studied. Nine strains of E. coli (seven O157:H7, one O111:H-, and one biotype 1 reference strain) were cultured individually for 18 h at 37°C in tryptic soy broth (TSB) plus 1% dextrose and in TSB without dextrose to yield acid resistance induced and noninduced stationary-phase cells, respectively. These cultures were then inoculated into brain heart infusion broth (BHI) supplemented with 0.5% citric, malic, lactic, or acetic acid and adjusted to pH 3.0 with HCl. The BHI tubes were incubated at 37°C for up to 7 h and samples were removed after 0, 2, 5, and 7 h and plated for counting CFU on BHI agar and MacConkey agar (MA). The results were compared to data previously obtained with HCl only. Acid resistance varied substantially among the isolates, being dependent on the strain, the acidulant, and the induction of pH-dependent acid resistance. Hydrochloric acid was consistently the least damaging to cells; lactic acid was the most detrimental. The relative activity of the other acids was strain dependent. Inducing pH-dependent acid resistance increased the already substantial acid tolerance of stationary-phase E. coli. The extent of injury also varied with acid and strain, with as much as a 5-log-cycle differential between BHI agar and MA CFU counts. The accurate determination of the survival of enterohemorrhagic E. coli in acidic foods must take into account the biological variability of the microorganism with respect to its acid resistance and its ability to enhance survival through the induction of physiological stress responses.

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.

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.

Escherichia coli O157:H7 Stationary-Phase Acid Resistance and Assessment of Survival in a Model Vegetable Fermentation System

2020 ◽  
Vol 83 (5) ◽  
pp. 745-753
Author(s):  
CLARA M. JONES ◽  
ROBERT E. PRICE ◽  
FRED BREIDT
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Stationary Phase ◽  
Limit Of Detection ◽  
Acid Resistance ◽  
Luria Broth ◽  
Acid Decarboxylase ◽  
Escherichia Coli O157 ◽  
Competitive Growth ◽  
Gastric Barrier

ABSTRACT Escherichia coli O157:H7 (STEC) acid resistance may aid the pathogen's ability to cross the human gastric barrier, which makes it an organism of concern in acidic foods. Our objective was to determine how STEC acid resistance may correlate with survival during vegetable fermentations. Seven E. coli O157:H7 strains were screened to assess acid resistance in simulated stomach acid at pH 2. The strains were separated into two groups that differed in acid resistance (P < 0.05), with three being acid sensitive and four acid resistant. The growth rates of these strains were measured in a Luria broth at pH values from 4.2 to 6.8. Two strains having similar growth kinetics, B201 (acid sensitive) and B241 (acid resistant), were selected for further analysis. B201 was found to be missing (compared with B241) two glutamic acid decarboxylase regulatory genes required for acid resistance, gadE and gadX. These strains were challenged in lactic acid (100 mM) solutions, including cucumber juice (CJ) media at pH 3.3. As expected, B201 was more acid sensitive than B241, and a filtered fermented CJ was more inhibitory than similarly acidified CJ. In competitive growth studies with Lactobacillus plantarum LA445 in CJ, B201 or B241 grew from approximately 104 to 108 CFU/mL within 24 h, but the STEC strains were below the limit of detection by 48 h. In all fermentations, L. plantarum reached 108 CFU/mL by 48 h. However, in three of four independent fermentation experiments, strain B201 survived longer than B241. This was possibly due to buffering in B241-LA445 fermentation brines that had increased lactic acid for a given pH compared with B201-LA445. These data indicate that stationary-phase acid resistance may not accurately predict STEC survival during vegetable fermentations. HIGHLIGHTS

scholarly journals Effect of Cattle Diet on Escherichia coli O157:H7 Acid Resistance

1999 ◽  
Vol 65 (7) ◽  
pp. 3233-3235 ◽  
Author(s):  
Carolyn J. Hovde ◽  
Paula R. Austin ◽  
Karen A. Cloud ◽  
Christopher J. Williams ◽  
Carl W. Hunt
Keyword(s):  
Escherichia Coli ◽  
Acid Resistance ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Human Infections

ABSTRACT The duration of shedding of Escherichia coli O157 isolates by hay-fed and grain-fed steers experimentally inoculated withE. coli O157:H7 was compared, as well as the acid resistance of the bacteria. The hay-fed animals shed E. coli O157 longer than the grain-fed animals, and irrespective of diet, these bacteria were equally acid resistant. Feeding cattle hay may increase human infections with E. coli O157:H7.

scholarly journals A pH-dependent conformational change in EspA, a component of the Escherichia coli O157:H7 type III secretion system

FEBS Journal ◽  
2005 ◽  
Vol 272 (11) ◽  
pp. 2773-2783 ◽  
Author(s):  
Tomoaki Kato ◽  
Daizo Hamada ◽  
Takashi Fukui ◽  
Makoto Hayashi ◽  
Takeshi Honda ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Conformational Change ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Escherichia Coli O157 ◽  
Type Iii ◽  
Ph Dependent

scholarly journals GadY, a Small-RNA Regulator of Acid Response Genes in Escherichia coli

2004 ◽  
Vol 186 (20) ◽  
pp. 6698-6705 ◽  
Author(s):  
Jason A. Opdyke ◽  
Ju-Gyeong Kang ◽  
Gisela Storz
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Small Rna ◽  
Acid Resistance ◽  
Base Pairs ◽  
Gene Encoding ◽  
Mrna Accumulation ◽  
Long Form ◽  
Genes Encoding ◽  
Opposite Strand

ABSTRACT A previous bioinformatics-based search for small RNAs in Escherichia coli identified a novel RNA named IS183. The gene encoding this small RNA is located between and on the opposite strand of genes encoding two transcriptional regulators of the acid response, gadX (yhiX) and gadW (yhiW). Given that IS183 is encoded in the gad gene cluster and because of its role in regulating acid response genes reported here, this RNA has been renamed GadY. We show that GadY exists in three forms, a long form consisting of 105 nucleotides and two processed forms, consisting of 90 and 59 nucleotides. The expression of this small RNA is highly induced during stationary phase in a manner that is dependent on the alternative sigma factor σS. Overexpression of the three GadY RNA forms resulted in increased levels of the mRNA encoding the GadX transcriptional activator, which in turn caused increased levels of the GadA and GadB glutamate decarboxylases. A promoter mutation which abolished gadY expression resulted in a reduction in the amount of gadX mRNA during stationary phase. The gadY gene was shown to overlap the 3′ end of the gadX gene, and this overlap region was found to be necessary for the GadY-dependent accumulation of gadX mRNA. We suggest that during stationary phase, GadY forms base pairs with the 3′-untranslated region of the gadX mRNA and confers increased stability, allowing for gadX mRNA accumulation and the increased expression of downstream acid resistance genes.

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