Performance of Some Heat-Sensitive Differential Agars Prepared and Melted by Microwave Energy1

1988 ◽  
Vol 51 (7) ◽  
pp. 577-578 ◽  
Author(s):  
C. LIANG ◽  
D. Y. C. FUNG
Keyword(s):  
Escherichia Coli ◽  
Cell Count ◽  
Viable Cell ◽  
Microwave Energy ◽  
Microwave Oven ◽  
Viable Cell Count ◽  
Streptococcus Faecalis ◽  
Cell Counts ◽  
Significant Difference ◽  
Conventional Boiling

The viable cell count performance of some heat-sensitive differential agars prepared and remelted by microwave energy was evaluated for Salmonella choleraesui, Streptococcus faecalis and Escherichia coli. The conventional boiling method was used for comparison. No significant difference was found between the microwave oven processed agar and the conventional-boiling processed agar in viable cell counts of the target bacteria. Heating and reheating of violet red bile agar, bismuth sulfite agar, and KF Streptococcus agar by both methods did not change agar performance. However, remelting of desoxycholate citrate agar by both methods resulted in a substantial lowering of viable cell counts.

scholarly journals Microbiological measurements for the development of a new preservation procedure for liquid egg

2011 ◽  
Vol 29 (No. 6) ◽  
pp. 569-574 ◽  
Author(s):  
C. Németh ◽  
B. Mráz ◽  
L. Friedrich ◽  
A. Suhajda ◽  
B. Janzsó ◽  
...  
Keyword(s):  
Shelf Life ◽  
Cell Count ◽  
Food Industry ◽  
Viable Cell ◽  
Viable Cell Count ◽  
Shell Eggs ◽  
Significant Difference ◽  
Egg Products ◽  
Powdered Form ◽  
Microbiological Status

Since recently, the food industry has been increasingly using ready-to-process egg products as the basic materials instead of shell eggs. Subsequent to breaking shell eggs and completing pasteurisation, they are put on the market as liquid egg products or in powdered form as dried eggs. Consumers prefer liquid eggs which better preserve the advantageous properties of natural eggs, however, their shelf life is short with quick spoilage. We have examined, how long heat treatment is needed at temperatures below pasteurisation to influence the microbiological status of liquid egg products and in this way also their shelf life. A significant difference was found between the microorganism reducing effects of the commonly used pasteurisation process and that of keeping liquid eggs at 55°C for 24 hours. While pasteurisation can only “considerably” reduce the viable cell count in liquid egg products, keeping the product at 55°C for 24 h would very probably result in no or very low viable cell count.

Melting Agar by Microwave Energy

1984 ◽  
Vol 47 (10) ◽  
pp. 770-772 ◽  
Author(s):  
DANIEL Y. C. FUNG ◽  
C. C. SHEREE LIN
Keyword(s):  
Room Temperature ◽  
Viable Cell ◽  
Microwave Treatment ◽  
Microwave Oven ◽  
Melting Time ◽  
Liquid Form ◽  
Cell Counts ◽  
Conventional Boiling ◽  
Composite Data

The microwave oven is very convenient for melting agar for viable cell counts. Composite data of four microwave ovens indicated that melting time for 50 ml of agar per bottle was about 1 min for one bottle, 1.5 min for two bottles, and 2.5 min for four bottles heated simultaneously. Melting time for 100 ml of agar per bottle was about 1.5 min for one bottle, 2.5 min for two bottles, and 4 min for four bottles. Melting times of agar in square or flat bottles were similar. Agar melted by microwave treatment performed in viable cell counts equally as well as agar melted by the conventional boiling method. Even after prolonged (50% longer than melting time) microwave treatment, performance of the agar remained unchanged. Agar melted by microwave treatment can remain in liquid form (48°C) in situ for about 30 min (50 ml) and 1 h (100 ml). When removed from the microwave oven immediately after melting, the agar remained in liquid form (48°C) at room temperature for about 25 min (50 ml) and 40 min (100 ml). The microwave oven is highly efficient in melting agar without detrimental effects on the performance of agar.

scholarly journals Plants used in Bandjoun village (La'Djo) to cure infectious diseases: An ethnopharmacology survey and in-vitro TimeKill Assessment of some of them against Escherichia coli

2016 ◽  
Vol 5 (2) ◽  
pp. 56-70
Author(s):  
S.P. Bouopda Tamo ◽  
◽  
S.H. Riwom Essama ◽  
F.X. Etoa ◽  
◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Medicinal Plants ◽  
Infectious Diseases ◽  
Cell Count ◽  
Plant Extracts ◽  
Viable Cell ◽  
Viable Cell Count ◽  
Minimal Bactericidal Concentration ◽  
Log Reduction

An ethnopharmacology survey concerning the medicinal plants used in Bandjoun village (La'Djo) to cure infectious diseases was carried out in three districts of this village. The survey led to the identification of 79 medicinal plants species listed in 41 families. These plants were cited to be use to treat about 25 infectious diseases among which malaria, diarrhea and intestinal-worms were the most cited. Chromolaena odorata, Voacanga africana, Moringa oleifera, Mammea africana, Euphorbia hirta, Psidium guajava, Allium cepa, Enantia chlorantha, Alstonia boonei and Picralima nitida, were the ten most cited plants. Extractions of parts of these last plants were performed in hydro-ethanol (3:7) solvent and then tested in-vitro against an Escherichia coli isolate. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were assessed by microdilution assay and the time-kill assessment was carried out by measure of log reduction in viable cell count, on a period of 48 hours. MIC and MBC determined were ranged between 1.00 and 32.0 mg/mL. Eighty percent (80%) of plant extracts tested have been bactericidal (MBC/MIC = 1 or 2) after 24 hours of incubation. A significant dose-dependent decreasing (P<0.05) in test organisms population was observed in the time with log reduction in viable cell count was ranged between 0.13 log10cfu/mL and 100% of inhibition. This antimicrobial activity has been attributed to metabolites groups in plant extracts namely, Phenols, flavonoids, tannins, coumarins, terpenoids, anthraquinones, cardiac glycosides, anthocyanides and alkaloids. These results obtained against Escherichia coli give a scientific validation to the traditional medical knowledge of Bandjoun-village populations and confirm some of the plants identified like a source of potentially active compounds against infectious diseases.

scholarly journals The dynamic balance of import and export of zinc in Escherichia coli suggests a heterogeneous population response to stress

2015 ◽  
Vol 12 (106) ◽  
pp. 20150069 ◽  
Author(s):  
Hiroki Takahashi ◽  
Taku Oshima ◽  
Jon L. Hobman ◽  
Neil Doherty ◽  
Selina R. Clayton ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Zinc Concentration ◽  
Systems Approach ◽  
Model Simulation ◽  
Dynamic Balance ◽  
Model Fitting ◽  
Viable Cell ◽  
Population Heterogeneity ◽  
Cell Counts ◽  
Import And Export

Zinc is essential for life, but toxic in excess. Thus all cells must control their internal zinc concentration. We used a systems approach, alternating rounds of experiments and models, to further elucidate the zinc control systems in Escherichia coli . We measured the response to zinc of the main specific zinc import and export systems in the wild-type, and a series of deletion mutant strains. We interpreted these data with a detailed mathematical model and Bayesian model fitting routines. There are three key findings: first, that alternate, non-inducible importers and exporters are important. Second, that an internal zinc reservoir is essential for maintaining the internal zinc concentration. Third, our data fitting led us to propose that the cells mount a heterogeneous response to zinc: some respond effectively, while others die or stop growing. In a further round of experiments, we demonstrated lower viable cell counts in the mutant strain tested exposed to excess zinc, consistent with this hypothesis. A stochastic model simulation demonstrated considerable fluctuations in the cellular levels of the ZntA exporter protein, reinforcing this proposal. We hypothesize that maintaining population heterogeneity could be a bet-hedging response allowing a population of cells to survive in varied and fluctuating environments.

scholarly journals THE EFFECTS OF SULFATHIAZOLE AND OF PROPYL CARBAMATE ON THE RATE OF OXYGEN CONSUMPTION AND GROWTH IN ESCHERICHIA COLI

1947 ◽  
Vol 30 (3) ◽  
pp. 263-278 ◽  
Author(s):  
Kenneth C. Fisher ◽  
Florence H. Armstrong
Keyword(s):  
Escherichia Coli ◽  
Oxygen Consumption ◽  
Cell Count ◽  
Optical Density ◽  
Viable Cell ◽  
E Coli ◽  
Rate Of Growth ◽  
A Value ◽  
Rate Of Oxygen Consumption ◽  
Rates Of Growth

1. The rates of growth and of oxygen consumption by cells of E. coli have been measured under identical conditions, and the effects of sulfathiazole (ST) and of n-propyl carbamate (PC) on these two processes have been compared. 2. The rate of growth was measured by (a) the increase in the viable cell count, (b) the increase in the optical density of the culture, (c) the increase in the rate of oxygen consumption, and (d) the decrease in the ammonia of the medium. The results as indicated by these several measures were identical under the conditions of these experiments. 3. Concentrations of ST or of PC which are just sufficient to stop growth completely, lower the rate of oxygen consumption per unit of bacterial protoplasm to a value approximately 50 per cent of that seen in the absence of the inhibitor. 4. It is shown that the rate of oxygen consumption in cells from old cultures is less affected by ST than is the rate of oxygen consumption by cells from young cultures. It is probable that the rate of oxygen consumption by "old" cells is lower than that of "young" cells. 5. The effects of ST and PC on both the rate of oxygen consumption and the rate of growth are very similar, indicating in a general way, that the mechanism of the actions of these two inhibitors is similar. Furthermore, since both of them produce appreciable inhibition of the rate of oxygen consumption while they are inhibiting growth, the possibility that the effect on oxygen consumption is the immediate cause of the effect on growth must be entertained.

Isolation and Purification of Colicin ECL 12, a Bacteriocin That Inhibits Strains of Escherichia coli O157:H7†

1997 ◽  
Vol 60 (12) ◽  
pp. 1520-1528 ◽  
Author(s):  
WANDA J. LYON ◽  
DENNIS G. OLSON
Keyword(s):  
Escherichia Coli ◽  
Proteolytic Enzymes ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Viable Cell ◽  
Exchange Chromatography ◽  
Isolation And Purification ◽  
E Coli ◽  
Log Reduction ◽  
Cell Counts

A swine fecal isolate, identified as Escherichia coli ECL12, was found to produce an antimicrobial substance designated as colicin ECL12. Colicin ECL12 was inhibitory against 20 strains of E. coli O157:H7 previously isolated from both human and bovine feces. Identification of the producer strain was determined phenotypically by biochemical and morphological tests. Colicin ECL12 was sensitive to several proteolytic enzymes. Adsorption of colicin ECL12 to sensitive cells of E. coli O157:H7 was bactericidal, resulting in a 2 log reduction in viable cell counts. Colicin ECL12 was purified from strain ECL12 by cell extraction and ion-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of colicin ECL12 resolved a single protein with a molecular weight of approximately 65,000.

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