Modelling inactivation of wild‐type and clinical Escherichia coli O26 strains using UV‐C and thermal treatment and subsequent persistence in simulated gastric fluid

2019 ◽  
Vol 127 (5) ◽  
pp. 1564-1575 ◽  
Author(s):  
V.S. Castro ◽  
D.K.A. Rosario ◽  
Y.S. Mutz ◽  
A.C.C. Paletta ◽  
E.E.S. Figueiredo ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thermal Treatment ◽  
Gastric Fluid ◽  
Simulated Gastric Fluid ◽  
Wild Type ◽  
Uv C

scholarly journals Adaptation of Escherichia coli O157:H7 to pH Alters Membrane Lipid Composition, Verotoxin Secretion, and Resistance to Simulated Gastric Fluid Acid

2004 ◽  
Vol 70 (6) ◽  
pp. 3500-3505 ◽  
Author(s):  
Hyun-Gyun Yuk ◽  
Douglas L. Marshall
Keyword(s):  
Escherichia Coli ◽  
Membrane Fluidity ◽  
Lipid Composition ◽  
Vaccenic Acid ◽  
Acid Resistance ◽  
Gastric Fluid ◽  
Membrane Lipid ◽  
Simulated Gastric Fluid ◽  
Acidic Ph ◽  
Membrane Lipid Composition

ABSTRACT The influence of adaptation to pH (from pH 5.0 to 9.0) on membrane lipid composition, verotoxin concentration, and resistance to acidic conditions in simulated gastric fluid (SGF) (pH 1.5, 37�C) was determined for Escherichia coli O157:H7 (HEC, ATCC 43895), an rpoS-deficient mutant of ATCC 43895 (HEC-RM, FRIK 816-3), and nonpathogenic E. coli (NPEC, ATCC 25922). Regardless of the strain, D values (in SGF) of acid-adapted cells were higher than those of non-acid-adapted cells, with HEC adapted at pH 5.0 having the greatest D value, i.e., 25.6 min. Acid adaptation increased the amounts of palmitic acid (C16:0) and decreased cis-vaccenic acid (C18:1ω7c) in the membrane lipids of all strains. The ratio of cis-vaccenic acid to palmitic acid increased at acidic pH, causing a decrease in membrane fluidity. HEC adapted to pH 8.3 and HEC-RM adapted to pH 7.3 exhibited the greatest verotoxin concentrations (2,470 and 1,460 ng/ml, respectively) at approximately 108 CFU/ml. In addition, the ratio of extracellular to intracellular verotoxin concentration decreased at acidic pH, possibly due to the decrease of membrane fluidity. These results suggest that while the rpoS gene does not influence acid resistance in acid-adapted cells it does confer decreased membrane fluidity, which may increase acid resistance and decrease verotoxin secretion.

scholarly journals Impact of Inoculum Preparation and Storage Conditions on the Response of Escherichia coli O157:H7 Populations to Undercooking and Simulated Exposure to Gastric Fluid

2006 ◽  
Vol 72 (1) ◽  
pp. 672-679 ◽  
Author(s):  
Jarret D. Stopforth ◽  
Panagiotis N. Skandamis ◽  
Laura V. Ashton ◽  
Ifigenia Geornaras ◽  
Patricia A. Kendall ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acid Tolerance ◽  
Storage Conditions ◽  
Gastric Fluid ◽  
Simulated Gastric Fluid ◽  
Tissue Samples ◽  
E Coli ◽  
Inoculum Preparation ◽  
The Impact ◽  
And Storage

ABSTRACT This study evaluated the impact of inoculum preparation and storage conditions on the response of Escherichia coli O157:H7 exposed to consumer-induced stresses simulating undercooking and digestion. Lean beef tissue samples were inoculated with E. coli O157:H7 cultures prepared in tryptic soy broth or meat decontamination runoff fluids (WASH) or detached from moist biofilms or dried biofilms formed on stainless steel coupons immersed in inoculated WASH. After inoculation, the samples were left untreated or dipped for 30 s each in hot (75°C) water followed by lactic acid (2%, 55°C), vacuum packaged, stored at 4 (28 days) or 12°C (16 days), and periodically transferred to aerobic storage (7°C for 5 days). During storage, samples were exposed to sequential heat (55°C; 20 min) and simulated gastric fluid (adjusted to pH 1.0 with HCl; 90 min) stresses simulating consumption of undercooked beef. Under the conditions of this study, cells originating from inocula of planktonic cells were, in general, more resistant to heat and acid than cells from cultures grown as biofilms and detached prior to meat inoculation. Heat and acid tolerance of cells on meat stored at 4°C was lower than that of cells on nondecontaminated meat stored at 12°C, where growth occurred during storage. Decontamination of fresh beef resulted in injury that inhibited subsequent growth of surviving cells at 12°C, as well as in decreases in resistance to subsequent heat and acid stresses. The shift of pathogen cells on beef stored under vacuum at 4°C to aerobic storage did not affect cell populations or subsequent survival after sequential exposure to heat and simulated gastric fluid. However, the transfer of meat stored under vacuum at 12°C to aerobic storage resulted in reduction in pathogen counts during aerobic storage and sensitization of survivors to the effects of sequential heat and acid exposure.

Comparative Effects of Thermal, High Hydrostatic Pressure, and UV-C Processing on the Quality, Nutritional Attributes, and Inactivation of Escherichia coli, Salmonella, and Listeria Introduced into Tiger Nut Milk

2019 ◽  
Vol 82 (6) ◽  
pp. 971-979 ◽  
Author(s):  
YAN ZHU ◽  
ASMA A. ELBRHAMI ◽  
VLADIMIR POPOVIĆ ◽  
TATIANA KOUTCHMA ◽  
KEITH WARRINER
Keyword(s):  
Escherichia Coli ◽  
Hydrostatic Pressure ◽  
Thermal Treatment ◽  
Vitamin C ◽  
High Hydrostatic Pressure ◽  
Color Change ◽  
Uv Light ◽  
Significant Loss ◽  
Total Phenolic ◽  
Uv C

ABSTRACT Tiger nut milk is a low-acid health beverage that is marketed with the claims of being high in protein, monounsaturated fatty acid (oleic acid), fiber, starch, and minerals, in addition to vitamins C and E. In this study, the effect of nonthermal processing with UV light (UV-C) or high hydrostatic pressure (HHP) on the nutritive content (protein, vitamin C, polyphenols, and antioxidant), and quality characteristics (viscosity and color) of tiger nut milk were compared with thermal processing. Baseline studies established the treatments parameters to support a >5-log CFU reduction of Escherichia coli P36, Listeria innocua ATCC 51742, and Salmonella Typhimurium WG49 introduced into tiger nut milk and then treated with thermal or nonthermal methods. The thermal treatment at 60°C for 30 min, HHP at 500 MPa for 120 s, and UV-C at 45.2 mJ cm−2 were required to achieve the target 5-log reduction. Thermal treatment resulted in a significant loss (P < 0.05) of total protein (34.9%), total phenolic content (28.7%), and vitamin C (27.1%) and negatively affected the tiger nut milk color, along with decreasing its viscosity. In contrast, HHP and UV-C light treatment retained protein and antioxidant content in tiger nut milk with no significant (P > 0.05) color change being recorded. Therefore, from a processing prospective, either UV-C light or HHP could be used to treat tiger nut milk, although additional hurdles to control the potential outgrowth of Clostridium botulinum during storage would be required. HIGHLIGHTS

scholarly journals Growth and Survival of Acid-Resistant and Non-Acid-Resistant Shiga-Toxin-ProducingEscherichia coliStrains during the Manufacture and Ripening of Camembert Cheese

2009 ◽  
Vol 2009 ◽  
pp. 1-10 ◽  
Author(s):  
M. P. Montet ◽  
E. Jamet ◽  
S. Ganet ◽  
M. Dizin ◽  
S. Miszczycha ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Gastric Fluid ◽  
Simulated Gastric Fluid ◽  
Growth And Survival ◽  
Cheese Making ◽  
Early Stages ◽  
Camembert Cheese

Growth and survival of acid-resistant (AR) and non-acid-resistant (NAR) Shiga-toxin-producingEscherichia coli(STEC) strains were investigated during the manufacture and ripening of microfiltered milk Camembert cheeses. The induction of acid resistance of the STEC strains in cheeses was also studied. Six different mixtures of AR and/or NAR STEC strains were inoculated separately into microfiltered milk at a level of103CFUmL−1. The STEC counts (AR and NAR) initially increased by 1 to 2log⁡10CFUg−1during cheese-making. Thereafter, the populations stabilized during salting/drying and then decreased during the early stages of ripening. Exposing the STEC strains in artificially inoculated cheeses to simulated gastric fluid (SGF - pH: 2.0) reduced the number of NAR strains to undetectable levels within 40 minutes, versus 120 minutes for the AR STEC strains. AR and NAR STEC were able to survive during the manufacture and ripening of Camembert cheese prepared from microfiltered milk with no evidence of induced acid tolerance in NAR STEC strains.

scholarly journals Stress Resistance Development and Genome-Wide Transcriptional Response ofEscherichia coliO157:H7 Adapted to Sublethal Thymol, Carvacrol, andtrans-Cinnamaldehyde

2018 ◽  
Vol 84 (22) ◽  
Author(s):  
Wenqian Yuan ◽  
Zi Jing Seng ◽  
Gurjeet Singh Kohli ◽  
Liang Yang ◽  
Hyun-Gyun Yuk
Keyword(s):  
Escherichia Coli ◽  
Stress Resistance ◽  
Virulence Genes ◽  
Acid Resistance ◽  
Gastric Fluid ◽  
Simulated Gastric Fluid ◽  
Cross Resistance ◽  
Resistance Development ◽  
Content Type ◽  
E Coli

ABSTRACTThymol, carvacrol, andtrans-cinnamaldehyde are essential oil (EO) compounds with broad-spectrum antimicrobial activities against foodborne pathogens, includingEscherichia coliO157:H7. However, little is known regarding direct resistance and cross-resistance development inE. coliO157:H7 after adaptation to sublethal levels of these compounds, and information is scarce on microbial adaptive responses at a molecular level. The present study demonstrated thatE. coliO157:H7 was able to grow in the presence of sublethal thymol (1/2T), carvacrol (1/2C), ortrans-cinnamaldehyde (1/2TC), displaying an extended lag phase duration and a lower maximum growth rate. EO-adapted cells developed direct resistance against lethal EO treatments and cross-resistance against heat (58°C) and oxidative (50 mM H2O2) stresses. However, no induction of acid resistance (simulated gastric fluid, pH 1.5) was observed. RNA sequencing revealed a large number (310 to 338) of differentially expressed (adjustedPvalue [Padj], <0.05; fold change, ≥5) genes in 1/2T and 1/2C cells, while 1/2TC cells only showed 27 genes with altered expression. In accordance with resistance phenotypes, the genes related to membrane, heat, and oxidative stress responses and genes related to iron uptake and metabolism were upregulated. Conversely, virulence genes associated with motility, biofilm formation, and efflux pumps were repressed. This study demonstrated the development of direct resistance and cross-resistance and characterized whole-genome transcriptional responses inE. coliO157:H7 adapted to sublethal thymol, carvacrol, ortrans-cinnamaldehyde. The data suggested that caution should be exercised when using EO compounds as food antimicrobials, due to the potential stress resistance development inE. coliO157:H7.IMPORTANCEThe present study was designed to understand transcriptomic changes and the potential development of direct and cross-resistance in essential oil (EO)-adaptedEscherichia coliO157:H7. The results demonstrated altered growth behaviors ofE. coliO157:H7 during adaptation in sublethal thymol, carvacrol, andtrans-cinnamaldehyde. Generally, EO-adapted bacteria showed enhanced resistance against subsequent lethal EO, heat, and oxidative stresses, with no induction of acid resistance in simulated gastric fluid. A transcriptomic analysis revealed the upregulation of related stress resistance genes and a downregulation of various virulence genes in EO-adapted cells. This study provides new insights into microbial EO adaptation behaviors and highlights the risk of resistance development in adapted bacteria.

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