scholarly journals Identification of Salmonella enterica Serovar Typhimurium Genes Important for Survival in the Swine Gastric Environment

2006 ◽  
Vol 72 (4) ◽  
pp. 2829-2836 ◽  
Author(s):  
Shawn M. D. Bearson ◽  
Bradley L. Bearson ◽  
Mark A. Rasmussen
Keyword(s):  
Lactic Acid ◽  
Salmonella Enterica ◽  
Ex Vivo ◽  
Stomach Contents ◽  
Acid Tolerance ◽  
Lethal Effect ◽  
Gastric Fluid ◽  
Low Ph ◽  
Chromatography Analysis ◽  
Serovar Typhimurium

ABSTRACT Since the stomach is a first line of defense for the host against ingested microorganisms, an ex vivo swine stomach contents (SSC) assay was developed to search for genes important for Salmonella enterica serovar Typhimurium survival in the hostile gastric environment. Initial characterization of the SSC assay (pH 3.87) using previously identified, acid-sensitive serovar Typhimurium mutants revealed a 10-fold decrease in survival for a phoP mutant following 20 min of challenge and no survival for mutants of rpoS or fur. To identify additional genes, a signature-tagged mutagenesis bank was constructed and screened in the SSC assay. Nineteen mutants were identified and individually analyzed in the SSC and acid tolerance response assays; 13 mutants exhibited a 10-fold or greater sensitivity in the SSC assay compared to the wild-type strain, but only 3 mutants displayed a 10-fold or greater decrease in survival following pH 3.0 acidic challenge. Further examination determined that the lethal effects of the SSC are pH dependent but that low pH is not the sole killing mechanism(s). Gas chromatography analysis of the SSC revealed lactic acid levels of 126 mM. Upon investigating the effects of lactic acid on serovar Typhimurium survival in a synthetic gastric fluid, not only was a concentration- and time-dependent lethal effect observed, but the phoP, rpoS, fur, and pnp genes were identified as involved in protection against lactic acid exposure. These studies indicate a role in gastric survival for several serovar Typhimurium genes and imply that the stomach environment is defined by more than low pH.

scholarly journals Salmonella enterica Serovar Typhimurium and Listeria monocytogenes Acid Tolerance Response Induced by Organic Acids at 20°C: Optimization and Modeling

2003 ◽  
Vol 69 (7) ◽  
pp. 3945-3951 ◽  
Author(s):  
E. J. Greenacre ◽  
T. F. Brocklehurst ◽  
C. R. Waspe ◽  
D. R. Wilson ◽  
P. D. G. Wilson
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Salmonella Enterica ◽  
Acid Tolerance ◽  
Acid Tolerance Response ◽  
Serovar Typhimurium ◽  
Tolerance Response ◽  
Acid Inactivation ◽  
Log Linear

ABSTRACT An acid tolerance response (ATR) has been demonstrated in Listeria monocytogenes and Salmonella enterica serovar Typhimurium in response to low pH poised (i.e., adapted) with acetic or lactic acids at 20°C and modeled by using dynamic differential equations. The ATR was not immediate or prolonged, and optimization occurred after exposure of L. monocytogenes for 3 h at pH 5.5 poised with acetic acid and for 2 h at pH 5.5 poised with lactic acid and after exposure of S. enterica serovar Typhimurium for 2 h at pH 5.5 poised with acetic acid and for 3 h at pH 5.5 poised with lactic acid. An objective mechanistic analysis of the acid inactivation data yielded estimates of the duration of the shoulder (t s ), the log-linear decline (k max), and the magnitude of a critical component (C). The magnitude of k max gave the best agreement with estimates of conditions for optimum ATR induction made from the raw data.

scholarly journals The Lactic Acid-Induced Acid Tolerance Response in Salmonella enterica Serovar Typhimurium Induces Sensitivity to Hydrogen Peroxide

2006 ◽  
Vol 72 (8) ◽  
pp. 5623-5625 ◽  
Author(s):  
E. J. Greenacre ◽  
S. Lucchini ◽  
J. C. D. Hinton ◽  
T. F. Brocklehurst
Keyword(s):  
Hydrogen Peroxide ◽  
Lactic Acid ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Acid Tolerance ◽  
Down Regulation ◽  
Acid Tolerance Response ◽  
Essential Component ◽  
Serovar Typhimurium ◽  
Tolerance Response

ABSTRACT Transcriptome analyses of Salmonella enterica serovar Typhimurium revealed that 15 genes were significantly up-regulated after 2 h of adaptation with lactic acid. cadB was the most highly up-regulated gene and was shown to be an essential component. Lactic acid-adapted cells exhibited sensitivity to hydrogen peroxide, likely due to down-regulation of the OxyR regulon.

scholarly journals Sanitation of fresh green asparagus and green onions inoculated with Salmonella

2009 ◽  
Vol 27 (No. 6) ◽  
pp. 454-462 ◽  
Author(s):  
M.A. Martínez-Téllez ◽  
F.J. Rodríguez-Leyva ◽  
I.E. Espinoza-Medina ◽  
I. Vargas-Arispuro ◽  
A.A. Gardea ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Lactic Acid ◽  
Exposure Time ◽  
Salmonella Enterica ◽  
Fresh Produce ◽  
Clean Water ◽  
Effective Agent ◽  
Serovar Typhimurium ◽  
Postharvest Handling ◽  
Green Asparagus

The absence of good agricultural and manufacturing practices in the production and postharvest handling of fresh produce, such as green asparagus or green onions increase the contamination risk by biological hazards like Salmonella. The objective of this work was to investigate the efficacy of chlorine (200 and 250 ppm), hydrogen peroxide (1.5% and 2%), and lactic acid (1.5% and 2%) sanitisers during different exposure times (40, 60, and 90 s) on the reduction of <i>Salmonella enterica</i> subspecie <i>enterica</i> serovar Typhimurium in inoculated fresh green asparagus and green onions. Washing with clean water only reduced < 1 log10 CFU/g in both vegetables. The most effective sanitiser evaluated for fresh green asparagus and green onions disinfection appeared to be 2% lactic acid reducing <i>Salmonella</i> growth close to 3 log<sub>10</sub> CFU/g. Hydrogen peroxide was the least effective agent for <i>Salmonella</i> Typhimurium reduction. No effect was observed of the exposure time of inoculated product to sanitiser up to 90 seconds. These results confirm that lactic acid could be used as an alternative for fresh green asparagus and green onions sanitation.

scholarly journals pH-, Lactic Acid-, and Non-Lactic Acid-Dependent Activities of Probiotic Lactobacilli against Salmonella enterica Serovar Typhimurium

2005 ◽  
Vol 71 (10) ◽  
pp. 6008-6013 ◽  
Author(s):  
Domitille Fayol-Messaoudi ◽  
Cédric N. Berger ◽  
Marie-Hélène Coconnier-Polter ◽  
Vanessa Liévin-Le Moal ◽  
Alain L. Servin
Keyword(s):  
Lactic Acid ◽  
Growth Phase ◽  
Salmonella Enterica ◽  
Lactobacillus Rhamnosus ◽  
Stationary Growth Phase ◽  
Exponential Growth Phase ◽  
Killing Activity ◽  
Serovar Typhimurium ◽  
Probiotic Strains ◽  
Probiotic Lactobacilli

ABSTRACT The mechanism(s) underlying the antibacterial activity of probiotic Lactobacillus strains appears to be multifactorial and includes lowering of the pH and the production of lactic acid and of antibacterial compounds, including bacteriocins and nonbacteriocin, non-lactic acid molecules. Addition of Dulbecco's modified Eagle's minimum essential medium to the incubating medium delays the killing activity of lactic acid. We found that the probiotic strains Lactobacillus johnsonii La1, Lactobacillus rhamnosus GG, Lactobacillus casei Shirota YIT9029, L. casei DN-114 001, and L. rhamnosus GR1 induced a dramatic decrease in the viability of Salmonella enterica serovar Typhimurium SL1344 mainly attributable to non-lactic acid molecule(s) present in the cell-free culture supernatant (CFCS). These molecules were more active against serovar Typhimurium SL1344 in the exponential growth phase than in the stationary growth phase. We also showed that the production of the non-lactic acid substance(s) responsible for the killing activity was dependent on growth temperature and that both unstable and stable substances with killing activity were present in the CFCSs. We found that the complete inhibition of serovar Typhimurium SL1344 growth results from a pH-lowering effect.

Activation of hilA expression at low pH requires the signal sensor CpxA, but not the cognate response regulator CpxR, in Salmonella enterica serovar Typhimurium

Microbiology ◽  
2003 ◽  
Vol 149 (10) ◽  
pp. 2809-2817 ◽  
Author(s):  
Shu-ichi Nakayama ◽  
Akira Kushiro ◽  
Takashi Asahara ◽  
Ryu-ichiro Tanaka ◽  
Lan Hu ◽  
...  
Keyword(s):  
Mutant Strain ◽  
Cell Invasion ◽  
Salmonella Enterica ◽  
Response Regulator ◽  
Low Ph ◽  
Apparent Difference ◽  
Virulence Determinants ◽  
Serovar Typhimurium ◽  
Cognate Response Regulator ◽  
Invasion Capacity

A two-component regulatory system, cpxR–cpxA, plays an important role in the pH-dependent regulation of virF, a global activator for virulence determinants including invasion genes, in Shigella sonnei. The authors examined whether the cpxR–cpxA homologues have some function in the expression of Salmonella enterica serovar Typhimurium invasion genes via the regulation of hilA, an activator for these genes. In a Salmonella cpxA mutant, the hilA expression level was reduced to less than 10 % of that in the parent strain at pH 6·0. This mutant strain also showed undetectable synthesis of an invasion gene product, SipC, at pH 6·0 and reduced cell invasion capacity – as low as 20 % of that of the parent. In this mutant, the reduction in hilA expression was much less marked at pH 8·0 than at pH 6·0 – no less than 50 % of that in the parent, and no significant reduction was observed in either SipC synthesis or cell invasion rate, compared to the parent. Unexpectedly, a Salmonella cpxR mutant strain and the parent showed no apparent difference in all three characteristics described above at either pH. These results indicate that in Salmonella, the sensor kinase CpxA activates hilA, and consequently, invasion genes and cell invasion capacity at pH 6·0. At pH 8·0, however, CpxA does not seem to have a large role in activation of these factors. Further, the results show that this CpxA-mediated activation does not require its putative cognate response regulator, CpxR. This suggests that CpxA may interact with regulator(s) other than CpxR to achieve activation at low pH.

scholarly journals Effects of Physical Properties of Feed on Microbial Ecology and Survival of Salmonella enterica Serovar Typhimurium in the Pig Gastrointestinal Tract

2004 ◽  
Vol 70 (6) ◽  
pp. 3485-3492 ◽  
Author(s):  
Lene Lind Mikkelsen ◽  
Patrick J. Naughton ◽  
Mette S. Hedemann ◽  
Bent Borg Jensen
Keyword(s):  
Lactic Acid ◽  
Gastrointestinal Tract ◽  
Salmonella Enterica ◽  
Death Rate ◽  
Gastric Content ◽  
The Other ◽  
Coliform Bacteria ◽  
Dry Matter Content ◽  
Distal Small Intestine ◽  
Serovar Typhimurium

ABSTRACT A two-by-two factorial experiment with pigs was conducted to study the effect of feed grinding (fine and coarse) and feed processing (pelleted and nonpelleted) on physicochemical properties, microbial populations, and survival of Salmonella enterica serovar Typhimurium DT12 in the gastrointestinal tracts of pigs. Results demonstrated a strong effect of diet on parameters measured in the stomachs of the pigs, whereas the effect was less in the other parts of the gastrointestinal tract. Pigs fed the coarse nonpelleted (C-NP) diet showed more solid gastric content with higher dry matter content than pigs fed the fine nonpelleted (F-NP), coarse pelleted (C-P), or fine pelleted (F-P) diet. Pigs fed the C-NP diet also showed significantly increased number of anaerobic bacteria (P < 0.05), increased concentrations of organic acids, and reduced pH in the stomach. In addition, pigs fed the C-NP diet showed increased in vitro death rate of S. enterica serovar Typhimurium DT12 in content from the stomach (P < 0.001). Pigs fed the C-NP diet had a significantly higher concentration of undissociated lactic acid in gastric content than pigs fed the other diets (P < 0.001). A strong correlation between the concentration of undissociated lactic acid and the death rate of S. enterica serovar Typhimurium DT12 was found. In the distal small intestine, cecum, and midcolon, significantly lower numbers of coliform bacteria were observed in pigs fed the coarse diets than in pigs fed the fine diets (P < 0.01). Pigs fed the C-NP diet showed the lowest number of coliform bacteria in these segments of the gastrointestinal tract. Pigs fed the coarse diets showed increased concentration of butyric acid in the cecum (P < 0.05) and colon (P < 0.10) compared with pigs fed the fine diets. It was concluded that feeding a coarsely ground meal feed to pigs changes the physicochemical and microbial properties of content in the stomach, which decreases the survival of Salmonella during passage through the stomach. In this way the stomach acts as a barrier preventing harmful bacteria from entering and proliferating in the lower part of the gastrointestinal tract.

scholarly journals CadC Has a Global Translational Effect during Acid Adaptation in Salmonella enterica Serovar Typhimurium

2007 ◽  
Vol 189 (6) ◽  
pp. 2417-2425 ◽  
Author(s):  
Yong Heon Lee ◽  
Bae Hoon Kim ◽  
Ji Hye Kim ◽  
Won Suck Yoon ◽  
Seong Ho Bang ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Acid Tolerance ◽  
Negative Influence ◽  
Acid Adaptation ◽  
Proteomic Approach ◽  
Serovar Typhimurium ◽  
Tolerance Response ◽  
Porin Proteins

ABSTRACT In Salmonella enterica serovar Typhimurium, the membrane-localized CadC is a transcriptional activator of the cadBA operon, which contributes to the acid tolerance response. Unlike in Escherichia coli, in which transcription of cadC is constitutive, in S. enterica serovar Typhimurium cadC expression is induced by low pH and lysine. Inactivation of cadC suppresses the acid-sensitive phenotype of a cadA mutation, suggesting the existence of other CadC-dependent genes in addition to the cadBA operon. Using a proteomic approach, we identified 8 of the putative CadC-induced proteins and 15 of the putative CadC-repressed proteins. The former include porin proteins OmpC and OmpF. The latter include proteins involved in glycolysis, energy production, and stress tolerance. To better understand the altered levels of OmpC and OmpF, we compared expression of ompR in S. enterica serovar Typhimurium wild-type and cadC mutant strains and determined that CadC exerted a negative influence on ompR transcription. Taken together, our findings strongly suggest that CadC may be a global regulator involved in the OmpR regulatory system during acid adaptation.

Survival of Escherichia coliO157:H7 in Synthetic Gastric Fluid after Cold and Acid Habituation in Apple Juice or Trypticase Soy Broth Acidified with Hydrochloric Acid or Organic Acids

1998 ◽  
Vol 61 (8) ◽  
pp. 939-947 ◽  
Author(s):  
HEIDI E. ULJAS ◽  
STEVEN C. INGHAM
Keyword(s):  
Lactic Acid ◽  
Citric Acid ◽  
Organic Acids ◽  
Apple Juice ◽  
Acid Tolerance ◽  
Storage Conditions ◽  
Gastric Fluid ◽  
E Coli ◽  
Storage Media ◽  
Strain Storage

Extreme acid tolerance of Escherichia coli O157:H7 has raised doubts about the safety of acidic foods. This study examined whether prior storage in acidic and/or cold conditions enhanced survival of E. coli O157 :H7 in synthetic gastric fluid (SGF). Three E. coli O157:H7 strains were stored in trypticase soy broth (TSB; acidified with HCl, malic acid, citric acid, or lactic acid) or pH 3.5 and 6.5 (nonacidic control) apple juice at 4 and 21°C for ≤7 days and then were incubated in pH 2.5 SGF at 37°C for 4 h. Cells survived better in apple juice than in TSB containing organic acids, suggesting that juice constituents other than organic acids protect E. coli O157:H7. Refrigeration combined with low pH best protected cells in apple juice and acidified TSB, but, compared to the nonacidic control, only acidified TSB enhanced subsequent survival in pH 2.5 SGF. Equal survival in SGF occurred after storage in pH 3.5 or 6.5 apple juice at 4°C, suggesting that low temperature alone in apple juice enhanced acid tolerance. Two strains stored at 4°C in TSB containing malic or citric acid subsequently survived better in SGF than cells stored in nonacidified TSB but poorer than cells stored in the presence of HCl. These differences reflect the higher pKa of these organic acids. However, subsequent survival of these strains in SGF was poorer after refrigerated storage in apple juice than in TSB containing citric or malic acids. Cells stored in lactic acid were most likely to be completely eliminated upon transfer to SGF. Differences in survival in storage media or SGF related to strain, storage conditions, or acidifier were consistent and often statistically significant (P &lt; 0.05). Although the survival of E. coli O157:H7 in refrigerated acidic beverages may not be affected by the type of acidifier used, the subsequent survival in SGF of this pathogen may be critically dependent on this factor.

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