Quality Control of Solid Culture Media: A Comparison of the Classic and the So‐called Ecometric Technique

Mossel, D. À. A.; Rossem, Francine Van; Koopmans, M.; Hendriks, M. A.; Verouden, Marjon; Eelderink, Ineke

doi:10.1111/j.1365-2672.1980.tb04719.x

Cited by 34 publications

(17 citation statements)

References 79 publications

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“…Since high ampicillin resistance (>100 µg/ml) of the strain to be GFP-labeled would interfere with selection of labeled transformants and possibly affect maintenance of the label in the presence of selection pressure, the ampicillin resistance profile for each strain to be labeled was determined by streaking fresh overnight culture onto a TSA plate supplemented with ampicillin (100 µg/ml or 150 µg/ml) using a semiquantitative scoring technique called ecometric evaluation [15], [16]. Only strains having absolute growth indices (AGIs) equal or less than 2 were selected for transformation.…”

Section: Methodsmentioning

confidence: 99%

Green Fluorescent Protein Labeling of Listeria, Salmonella, and Escherichia coli O157:H7 for Safety-Related Studies

Zhang

Doyle

2011

PLoS ONE

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Many food safety-related studies require tracking of introduced foodborne pathogens to monitor their fate in complex environments. The green fluorescent protein (GFP) gene (gfp) provides an easily detectable phenotype so has been used to label many microorganisms for ecological studies. The objectives of this study were to label major foodborne pathogens and related bacteria, including Listeria monocytogenes, Listeria innocua, Salmonella, and Escherichia coli O157:H7 strains, with GFP and characterize the labeled strains for stability of the GFP plasmid and the plasmid's effect on bacterial growth. GFP plasmids were introduced into these strains by a CaCl2 procedure, conjugation or electroporation. Stability of the label was determined through sequential propagation of labeled strains in the absence of selective pressure, and rates of plasmid-loss were calculated. Stability of the GFP plasmid varied among the labeled species and strains, with the most stable GFP label observed in E. coli O157:H7. When grown in nonselective media for two consecutive subcultures (ca. 20 generations), the rates of plasmid loss among labeled E. coli O157:H7, Salmonella and Listeria strains ranged from 0%–30%, 15.8%–99.9% and 8.1%–93.4%, respectively. Complete loss (>99.99%) of the plasmid occurred in some labeled strains after five consecutive subcultures in the absence of selective pressure, whereas it remained stable in others. The GFP plasmid had an insignificant effect on growth of most labeled strains. E. coli O157:H7, Salmonella and Listeria strains can be effectively labeled with the GFP plasmid which can be stable in some isolates for many generations without adversely affecting growth rates.

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Section: Methodsmentioning

confidence: 99%

Green Fluorescent Protein Labeling of Listeria, Salmonella, and Escherichia coli O157:H7 for Safety-Related Studies

Zhang

Doyle

2011

PLoS ONE

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“…Before use all batches of this medium were checked for the absence of inhibitory properties towards nonstressed Enterobacteriaceae by the ecometric method of Mossel et al (1978). It had the following composition (g/l of water): yeast extract powder, 3.0; peptone, 7.0; NaCl, 5.0; bile salts, 1.5; glucose, 10.0; neutral red, 0.03; crystal violet 0.002; agar, 15.0; pH, 7.4.…”

Section: Mueller-hinton Agar With Polyziitex' Supplementmentioning

confidence: 99%

Comparison of the Effects of Liquid Medium Repair and the Incorporation of Catalase in MacConkey Type Media on the Recovery of Enterobacteriaceae Sublethally Stressed by Freezing

Mossel¹,

Veldman²,

Eelderink³

1980

Journal of Applied Bacteriology

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Nine pure cultures of species of Enterobacteriaceae were stressed by rapid freezing in tryptone soya broth (TSB) to — 22°C and subsequent storage at that temperature for 7 d. About one to two log cycles kill and at least one additional log cycle sublethal impairment was achieved. Numbers of colonies of these cultures in poured plates of violet red bile glucose (VRBG) agar, with 67 u/ml of catalase added at 47°C, were only slightly higher than those in plain VRBG, both incubated overnight at 30°C. Two hours incubation of TSB suspensions at 17–25° C resulted in almost complete restoration of the ability of cells to develop colonies in VRBG, without, however, leading to any significant multiplication. Similar experiments with 32 samples of frozen minced meat, 27 samples of frozen surface water, 18 of frozen chicken liver and 14 of fresh sausage substantiated the results obtained in the studies on pure cultures. In the experiments with the nine pure cultures the influence of the nutrient composition of the solid enumeration media: ‘minimal’ agar, TSB agar (TSBA) and Mueller‐Hinton agar with Polyvitex nutrient supplement (MHA), on the recovery of Enterobacteriaceae stressed by freezing was also studied. Colony numbers in TSBA and MHA were virtually identical. The glucose mineral salts medium led to lower recovery, indicating that so‐called ‘minimal medium recovery’ of stressed bacterial populations is not a common phenomenon.

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“…A 0.1-ml aliquot of the culture was streaked onto TSA-YE (tryptone soya agar [CM 131; Oxoid] with 0.6% yeast extract [L21; Oxoid]) and incubated at 30°C for 24 to 48 h. Typical L. monocytogenes colonies were subcultured onto Oxford Formulation Listeria Selective Agar (Oxoid CM856 including selective supplement Oxoid SR140) and incubated at 37°C for 24 to 48 h. If we saw only one colony type on TSA-YE and if colonies typical of Listeria were seen on Oxford Formulation Listeria selective agar, then growth of L. monocytogenes was presumed confirmed. When turbidity did not increase, or if only a deposit formed in the bottom of the well by the end of the incubation period, we used a standardized ecometric technique (29,30,33) calibrated to viable counts to identify culture conditions that were lethal to L. monocytogenes, i.e., in which cell numbers declined during incubation. These determinations could not be made using turbidimetric methods alone.…”

Section: Methodsmentioning

confidence: 99%

Growth Limits of Listeria monocytogenes as a Function of Temperature, pH, NaCl, and Lactic Acid

Tienungoon

Ratkowsky

McMeekin

et al. 2000

Appl Environ Microbiol

219

111

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Models describing the limits of growth of pathogens under multiple constraints will aid management of the safety of foods which are sporadically contaminated with pathogens and for which subsequent growth of the pathogen would significantly increase the risk of food-borne illness. We modeled the effects of temperature, water activity, pH, and lactic acid levels on the growth of two strains of Listeria monocytogenes in tryptone soya yeast extract broth. The results could be divided unambiguously into "growth is possible" or "growth is not possible" classes. We observed minor differences in growth characteristics of the two L. monocytogenes strains. The data follow a binomial probability distribution and may be modeled using logistic regression. The model used is derived from a growth rate model in a manner similar to that described in a previously published work (K. A. Presser, T. Ross, and D. A. Ratkowsky, Appl. Environ. Microbiol. 64:1773-1779, 1998). We used "nonlinear logistic regression" to estimate the model parameters and developed a relatively simple model that describes our experimental data well. The fitted equations also described well the growth limits of all strains of L. monocytogenes reported in the literature, except at temperatures beyond the limits of the experimental data used to develop the model (3 to 35°C). The models developed will improve the rigor of microbial food safety risk assessment and provide quantitative data in a concise form for the development of safer food products and processes.Predictive microbiology combines mathematical modeling with experimental data on combinations of factors that influence the growth of food spoilage and/or food-borne pathogenic microorganisms. The models developed are intended to predict the fate of microorganisms in foods. Since the experimental data are usually derived from studies using laboratory media, the models must be validated with data collected under conditions under which food products are customarily stored.Predictive microbiology models can be divided into kinetic models and probability models. With the former type, one calculates the microbiological life of food products, i.e., the period of time during which the number of microorganisms in the food is less than a specified value. With the latter type, one determines whether a microorganism can grow and identifies storage conditions with a low or nil probability of growth.Kinetic and probability models may be closely related, because the probability of detectable growth within a specified time period depends on germination, lag, and generation times, i.e., on kinetic parameters. In some cases, a probability model may be derived from a kinetic model by some simple mathematical transformations. For example, in references 33, 35 and 41, a kinetic model was transformed into a probability model by taking the natural logarithm of both sides of the original equation and then replacing one side with the "logit" of a probability, i.e., ln [P/(1 Ϫ P)], where P is the probability that growth occurs...

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Quality Control of Solid Culture Media: A Comparison of the Classic and the So‐called Ecometric Technique

Cited by 34 publications

References 79 publications

Green Fluorescent Protein Labeling of Listeria, Salmonella, and Escherichia coli O157:H7 for Safety-Related Studies

Green Fluorescent Protein Labeling of Listeria, Salmonella, and Escherichia coli O157:H7 for Safety-Related Studies

Comparison of the Effects of Liquid Medium Repair and the Incorporation of Catalase in MacConkey Type Media on the Recovery of Enterobacteriaceae Sublethally Stressed by Freezing

Growth Limits of Listeria monocytogenes as a Function of Temperature, pH, NaCl, and Lactic Acid

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