Differentiation of the Effects of pH and Lactic or Acetic Acid Concentration on the Kinetics of Listeria Monocytogenes Inactivation

Buchanan, Robert L.; Golden, M.H.; Whiting, Richard C.

doi:10.4315/0362-028x-56.6.474

Cited by 144 publications

(83 citation statements)

References 40 publications

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“…These D values are very similar to those we reported previously for 7H9-OADC medium (pH 6.8)-grown M. paratuberculosis (37) but higher than those previously reported for other bacterial pathogens. Acid survival D values for Yersinia enterocolitica O:3 were from 0.4 to 0.6 days at test pH 4 (24), and D values reported for Listeria monocytogenes were 0.5, 1.2, and 3.6 days at test pH 4, 5, and 6, respectively (1).…”

Section: Discussionmentioning

confidence: 89%

Variation in Resistance of Mycobacterium paratuberculosis to Acid Environments as a Function of Culture Medium

Sung

Collins

2003

Appl Environ Microbiol

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Acid resistance of Mycobacterium paratuberculosis was examined as a function of growth conditions (i.e., in vitro growth medium and pH). M. paratuberculosis was cultured in either fatty acid-containing medium (7H9-OADC) or glycerol-containing medium (WR-GD or 7H9-GD) at two culture pHs (pHs 6.0 and 6.8). Organisms produced in these six medium and pH conditions were then tested for resistance to acetate buffer at pHs 3, 4, 5, and 6 at 20°C. A radiometric culture method (BACTEC) was used to quantify viable M. paratuberculosis cell data at various acid exposure times, and D values (decimal reduction times, or the times required to kill a 1-log 10 concentration of bacteria) were determined. Soluble proteins of M. paratuberculosis grown under all six conditions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to identify proteins that may be associated with acid resistance or susceptibility. The culture medium affected growth rate and morphology: thin floating sheets of cells were observed in 7H9-OADC versus confluent, thick, waxy, and wrinkled pellicles in WR-GD. Culture medium pH affected growth rate (which was highest at pH 6.0), but it had little or no Mycobacterium paratuberculosis, also known as Mycobacterium avium subsp. paratuberculosis, is the cause of Johne's disease, a widespread chronic granulomatous inflammatory bowel disease of dairy cattle and other ruminants (5,6,40). Several reports indicate a significant association of M. paratuberculosis with a similar inflammatory bowel disease of humans called Crohn's disease (2,7,11,16,23,28). Whether this is a causal association remains controversial (17, 41).There are a number of routes for human exposure to M. paratuberculosis. Foods of animal origin (and dairy products in particular) have received the most attention. Consequently, the ability of M. paratuberculosis to resist heat (such as during pasteurization) and chemical factors important in food preservation (such as low pH and high salt concentration) has become important in the field of M. paratuberculosis research (13-15, 19, 30, 34, 36, 37).We previously reported rates of survival of M. paratuberculosis in a soft white Hispanic-style cheese made from M. paratuberculosis-spiked milk (37). The decimal reduction times (D values [i.e., times required for a 1-log 10 reduction in viable counts]) were 36.5 and 59.9 days for cheese made from heattreated and non-heat-treated M. paratuberculosis-spiked milk, respectively. Similar D values for M. paratuberculosis in Swiss hard (27.8 days) and semihard (45.5 days) cheeses were reported by Spahr and Schafroth (34).Low pH appeared to be one of the factors in cheese production that are important in affecting M. paratuberculosis survival (37). The present study was undertaken to further characterize acid resistance of M. paratuberculosis and determine the degree to which in vitro culture conditions affect the outcome of pH resistance studies. MATERIALS AND METHODSM. paratuberculosis strains. Three bovine M. paratuberculosis strai...

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Section: Discussionmentioning

confidence: 89%

Variation in Resistance of Mycobacterium paratuberculosis to Acid Environments as a Function of Culture Medium

Sung

Collins

2003

Appl Environ Microbiol

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“…Glass et al (13) reported that populations of L. monocytogenes exhibited a decrease of 0.6 log 10 CFU/g in cheese (pH 5.6 to 5.84, 2.3 to 2.6% salt) stored for 4 days at 30°C. However, Buchanan et al (2) published a D value for L. monocytogenes in brain heart infusion broth (pH 5.0, acidified with 50 mM acetic acid) of 1.2 days at 28°C. That means the organism should have exhibited a decrease of 4 log 10 CFU/ml in the brain heart infusion broth during 4 days of storage based on the D value reported by Buchanan et al, but a reduction of only 0.6 log 10 CFU/g was found in cheese.…”

Section: Vol 66 2000mentioning

confidence: 99%

Effect of Three Factors in Cheese Production (pH, Salt, and Heat) on Mycobacterium avium subsp. paratuberculosis Viability

Sung

Collins

2000

Appl Environ Microbiol

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“…A bacterial strain can produce different shapes of survival curves. Frequently, concave curves may become convex or sigmoidal when the intensity of the stress varies (6,7,10,19,24,38,45,47,48). The patterns of survival curves may also vary with the physiological state of the cells and are dependent on the phase of growth (exponential or stationary phase) and also on the conditions of adaptation before the stress (18,25,36).…”

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confidence: 99%

General Model, Based on Two Mixed Weibull Distributions of Bacterial Resistance, for Describing Various Shapes of Inactivation Curves

Coroller¹,

Leguérinel²,

Mettler³

et al. 2006

Appl Environ Microbiol

181

110

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Cells of Listeria monocytogenes or Salmonella enterica serovar Typhimurium taken from six characteristic stages of growth were subjected to an acidic stress (pH 3.3). As expected, the bacterial resistance increased from the end of the exponential phase to the late stationary phase. Moreover, the shapes of the survival curves gradually evolved as the physiological states of the cells changed. A new primary model, based on two mixed Weibull distributions of cell resistance, is proposed to describe the survival curves and the change in the pattern with the modifications of resistance of two assumed subpopulations. This model resulted from simplification of the first model proposed. These models were compared to the Whiting's model. The parameters of the proposed model were stable and showed consistent evolution according to the initial physiological state of the bacterial population. Compared to the Whiting's model, the proposed model allowed a better fit and more accurate estimation of the parameters. Finally, the parameters of the simplified model had biological significance, which facilitated their interpretation.When thermal or nonthermal inactivation of spores or vegetative microorganisms is considered, the log-linear shape of bacterial survival curves is a particular case among types of curves (12,17,43,49). In the case of nonthermal inactivation caused by unfavorable environmental conditions, the shape of curves indicates more pronounced heterogeneity according to the intensity of the stress. A bacterial strain can produce different shapes of survival curves. Frequently, concave curves may become convex or sigmoidal when the intensity of the stress varies (6,7,10,19,24,38,45,47,48). The patterns of survival curves may also vary with the physiological state of the cells and are dependent on the phase of growth (exponential or stationary phase) and also on the conditions of adaptation before the stress (18,25,36).In order to model nonthermal inactivation curves, a number of primary models have been proposed. Among these models are the vitalistic models proposed by Cole et al. (13,28,39), models describing both growth and inactivation (26,27,32,37,40,41), the modified Gompertz model (24, 32), the exponential model (31), and the log-linear model with latency time (6) and/or with a tail (5). These models cannot deal with all shapes of curves, and most of them are based on log-linear inactivation.Some models can describe non-log-linear decrease or sigmoidal inactivation curves. The Weibull model has largely been used in thermal and nonthermal treatment studies. It is based on the hypothesis that the resistance to stress of a population follows a Weibull distribution (14,19,34,44,45). This type of model can describe linear, concave, or convex curves. It was modified and extended to sigmoidal curves in heat treatment studies (2). The model of Baranyi and Roberts (3) and the model of Geeraerd et al. (17) can describe a linear shape with or without shoulder or tail and sigmoidal shapes (21,22). These models, which can...

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Differentiation of the Effects of pH and Lactic or Acetic Acid Concentration on the Kinetics of Listeria Monocytogenes Inactivation

Cited by 144 publications

References 40 publications

Variation in Resistance of Mycobacterium paratuberculosis to Acid Environments as a Function of Culture Medium

Variation in Resistance of Mycobacterium paratuberculosis to Acid Environments as a Function of Culture Medium

Effect of Three Factors in Cheese Production (pH, Salt, and Heat) on Mycobacterium avium subsp. paratuberculosis Viability

General Model, Based on Two Mixed Weibull Distributions of Bacterial Resistance, for Describing Various Shapes of Inactivation Curves

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