Faculty Opinions recommendation of Role of Listeria monocytogenes sigma(B) in survival of lethal acidic conditions and in the acquired acid tolerance response.

For several foodborne bacterial pathogens, an acid tolerance response appears to be an important strategy for counteracting acid stress imposed either during food processing or by the human host. The acid tolerance response enhances bacterial survival of lethal acid challenge following prior exposure to sublethal acidic conditions. Previous studies have revealed relationships between a foodborne pathogen's ability to survive acid challenge and its infectious dose. Vibrio parahaemolyticus is capable of causing gastroenteritis when sufficient cells of pathogenic strains are consumed. This study was designed to characterize acid sensitivities and to compare the effects of sublethal acid exposure (adaptation) on survival capabilities and cytotoxicities of different V. parahaemolyticus strains. Survival of acid challenge by stationary-phase cells differed by up to 3 log CFU/ml among the 25 isolates tested. No differences in acid resistance were found between strains when they were grouped by source (clinical isolates versus those obtained from food). Survival at pH 3.6 for log-phase cells that had been previously exposed to sublethal acidic conditions (pH 5.5) was enhanced compared with that for cells not previously exposed to pH 5.5. However, for stationary-phase cells, exposure to pH 5.5 impaired both subsequent survival at pH 3.6 and cytotoxicity to human epithelial cells. Relative cytotoxicities of nonadapted stationary-phase cells were 1.2- to 4.8-fold higher than those of adapted cells. Sublethal acid exposure appears to impose measurable growth phase–dependent effects on subsequent lethal acid challenge survival and cytotoxicity of V. parahaemolyticus.

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The Acid Tolerance Response Alters Membrane Fluidity and Induces Nisin Resistance in Listeria monocytogenes

Probiotics and Antimicrobial Proteins ◽

10.1007/s12602-009-9025-8 ◽

2009 ◽

Vol 1 (2) ◽

pp. 130-135 ◽

Cited By ~ 2

Author(s):

Mohamed Z. Badaoui Najjar ◽

Michael L. Chikindas ◽

Thomas J. Montville

Keyword(s):

Listeria Monocytogenes ◽

Membrane Fluidity ◽

Acid Tolerance ◽

Acid Tolerance Response ◽

Tolerance Response

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

Applied and Environmental Microbiology ◽

10.1128/aem.69.7.3945-3951.2003 ◽

2003 ◽

Vol 69 (7) ◽

pp. 3945-3951 ◽

Cited By ~ 64

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.

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Influence of the Natural Microbial Flora on the Acid Tolerance Response of Listeria monocytogenes in a Model System of Fresh Meat Decontamination Fluids

Applied and Environmental Microbiology ◽

10.1128/aem.67.6.2410-2420.2001 ◽

2001 ◽

Vol 67 (6) ◽

pp. 2410-2420 ◽

Cited By ~ 41

Author(s):

John Samelis ◽

John N. Sofos ◽

Patricia A. Kendall ◽

Gary C. Smith

Keyword(s):

Listeria Monocytogenes ◽

Microbial Growth ◽

Bacterial Pathogens ◽

Acid Tolerance ◽

Fresh Meat ◽

Acid Tolerance Response ◽

Plant Environment ◽

Natural Flora ◽

Tolerance Response ◽

Acid Tolerant

ABSTRACT Depending on its composition and metabolic activity, the natural flora that may be established in a meat plant environment can affect the survival, growth, and acid tolerance response (ATR) of bacterial pathogens present in the same niche. To investigate this hypothesis, changes in populations and ATR of inoculated (105 CFU/ml)Listeria monocytogenes were evaluated at 35°C in water (10 or 85°C) or acidic (2% lactic or acetic acid) washings of beef with or without prior filter sterilization. The model experiments were performed at 35°C rather than lower (≤15°C) temperatures to maximize the response of inoculated L. monocytogenes in the washings with or without competitive flora. Acid solution washings were free (<1.0 log CFU/ml) of natural flora before inoculation (day 0), and no microbial growth occurred during storage (35°C, 8 days). Inoculated L. monocytogenes died off (negative enrichment) in acid washings within 24 h. In nonacid (water) washings, the pathogen increased (approximately 1.0 to 2.0 log CFU/ml), irrespective of natural flora, which, when present, predominated (>8.0 log CFU/ml) by day 1. The pH of inoculated water washings decreased or increased depending on absence or presence of natural flora, respectively. These microbial and pH changes modulated the ATR of L. monocytogenes at 35°C. In filter-sterilized water washings, inoculated L. monocytogenes increased its ATR by at least 1.0 log CFU/ml from days 1 to 8, while in unfiltered water washings the pathogen was acid tolerant at day 1 (0.3 to 1.4 log CFU/ml reduction) and became acid sensitive (3.0 to >5.0 log CFU/ml reduction) at day 8. These results suggest that the predominant gram-negative flora of an aerobic fresh meat plant environment may sensitize bacterial pathogens to acid.

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