scholarly journals Acid Tolerance Response of Listeria monocytogenes in Various External pHs with Different Concentrations of Lactic Acid

2020 ◽  
Vol 17 (4) ◽  
pp. 253-261
Author(s):  
Yunge Liu ◽  
Lixian Zhu ◽  
Pengcheng Dong ◽  
Rongrong Liang ◽  
Yanwei Mao ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Acid Tolerance ◽  
Acid Tolerance Response ◽  
Tolerance Response

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

2001 ◽  
Vol 67 (6) ◽  
pp. 2410-2420 ◽  
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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