Detection of Viable but Nonculturable Cells of L isteria monocytogenes with the Use of Direct Epifluorescent Filter Technique

2014 ◽  
Vol 35 (1) ◽  
pp. 86-90 ◽  
Author(s):  
Magdalena A. Olszewska ◽  
Helena Panfil-Kuncewicz ◽  
Łucja Łaniewska-Trokenheim
Keyword(s):  
Viable But Nonculturable ◽  
Filter Technique ◽  
Nonculturable Cells ◽  
Direct Epifluorescent Filter Technique

SIGNIFICANCE OF VIABLE BUT NONCULTURABLE BACTERIA FOR SAFETY OF FOOD PRODUCTS

2019 ◽  
Vol 1 (2) ◽  
pp. 183-189
Author(s):  
A. M. Abdullaeva ◽  
◽  
L. P. Blinkova ◽  
Yu. D. Pakhomov ◽  
◽  
...  
Keyword(s):  
Food Products ◽  
Active State ◽  
Insufficient Data ◽  
Main Hypothesis ◽  
Viable But Nonculturable ◽  
Nonculturable Cells

In this review data on hazardous influence of nonculturable cells of pathogens on humans and animals, of contamination of foodstuffs is presented and also attention is stressed on properties of such cells and their effect through foodstuffs on humans and animals. Main hypothesis of formation and resuscitation of viable but nonculturable cells are elucidated. Factors that influence shifting bacteria to nonculturability and their conversion into active state are discussed. The conclusion is drawn about biohazard of viable nonculturable cells and insufficient data about their physiology and mechanisms of transition into this state and resuscitation back.

Determination of Viable Bacterial Populations in Raw Milk within 20 Minutes by Using a Direct Epifluorescent Filter Technique

1997 ◽  
Vol 60 (7) ◽  
pp. 874-876 ◽  
Author(s):  
CLAUDE P. CHAMPAGNE ◽  
NANCY J. GARDNER ◽  
JULIE FONTAINE ◽  
JACQUES RICHARD
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
Bacterial Populations ◽  
Filter Technique ◽  
Milk Samples ◽  
Standard Plate ◽  
Plate Counts ◽  
Direct Epifluorescent Filter Technique ◽  
Triton X

The results from a shortened procedure for the direct epifluorescent filter technique (DEFT) determination of viable bacterial populations in raw milk were compared to standard plate counts. Shortening the prefiltration trypsin-Triton X-100 incubation period from 10 to 3 min enabled the completion of the analysis within 20 min. The short DEFT method results had a correlation coefficient (r) of 0.81 with plate counts. With respect to precision, the average difference between values of duplicate plate count analyses was 0.16 log units; that of the short DEFT was 0.14 log units. The slopes of the regressions equations were less than 1, indicating that a direct correlation is not achieved. Short DEFT values were 0.17 log units higher than those of plate counts on milk samples containing less than 10,000 CFU/ml. For milk samples containing counts over 10,000 CFU/ml, short DEFT values averaged only 0.05 log units above plate count readings. Daily preparation of the stain appears unnecessary since acridine orange solutions stored for up to 2 days at 4°C did not produce results significantly (P > 0.05) different from those obtained with fresh solutions. The short DEFT method has potential for the assessment of the bacteriological quality of raw milk in tanker deliveries.

The Limulus Amoebocyte Lysate Assay and the Direct Epifluorescent Filter Technique as Estimators of Potential Shelf-life of Pasteurized Fluid Milk

1990 ◽  
Vol 53 (2) ◽  
pp. 151-153 ◽  
Author(s):  
ROBERT D. BYRNE ◽  
J. RUSSELL BISHOP
Keyword(s):  
Shelf Life ◽  
Benzalkonium Chloride ◽  
Detection Techniques ◽  
Filter Technique ◽  
Psychrotrophic Bacteria ◽  
Limulus Amoebocyte Lysate ◽  
Whole Milk ◽  
Before And After ◽  
Direct Epifluorescent Filter Technique ◽  
Fluid Milk

The Limulus Amoebocyte Lysate Assay, Direct Epifluorescent Filter Technique and modified Psychrotrophic Bacteria Count were used to indicate potential shelf-life of pasteurized fluid milk. Commercial whole milk samples, stored at 7°C, were analyzed for bacterial and biochemical parameters, as well as for potential shelf-life by daily sensory evaluation. Each sample was evaluated before and after the following preliminary incubations: milk alone, milk with benzalkonium chloride, milk and broth, and milk and broth with benzalkonium chloride. The Limulus Amoebocyte Lysate Assay, Direct Epifluorescent Filter Technique, and modified Psychrotrophic Bacteria Count in conjunction with the preliminary incubations, produced relatively high correlations to shelf-life (−0.78, −0.85, and −0.86 respectively). Thus, these bacterial detection techniques could be used as rapid methods of shelf-life estimation.

scholarly journals Respective Roles of Culturable and Viable-but-Nonculturable Cells in the Heterogeneity of Salmonella enterica Serovar Typhimurium Invasiveness

2009 ◽  
Vol 75 (16) ◽  
pp. 5179-5185 ◽  
Author(s):  
Julien Passerat ◽  
Patrice Got ◽  
Sam Dukan ◽  
Patrick Monfort
Keyword(s):  
Stationary Phase ◽  
Salmonella Enterica ◽  
Gradient Centrifugation ◽  
Health Concern ◽  
Viable But Nonculturable ◽  
Serovar Typhimurium ◽  
Nonculturable Cells ◽  
Sources Of Infection ◽  
Culturable Cell ◽  
Vbnc Cell

ABSTRACT The existence of Salmonella enterica serovar Typhimurium viable-but-nonculturable (VBNC) cells is a public health concern since they could constitute unrecognized sources of infection if they retain their pathogenicity. To date, many studies have addressed the ability of S. Typhimurium VBNC cells to remain infectious, but their conclusions are conflicting. An assumption could explain these conflicting results. It has been proposed that infectivity could be retained only temporarily after entry into the VBNC state and that most VBNC cells generated under intense stress could exceed the stage where they are still infectious. Using a Radioselectan density gradient centrifugation technique makes it possible to increase the VBNC-cell/culturable-cell ratio without increasing the exposure to stress and, consequently, to work with a larger proportion of newly VBNC cells. Here, we observed that (i) in the stationary phase, the S. Typhimurium population comprised three distinct subpopulations at 10, 24, or 48 h of culture; (ii) the VBNC cells were detected at 24 and 48 h; (iii) measurement of invasion gene (hilA, invF, and orgA) expression demonstrated that cells are highly heterogeneous within a culturable population; and (iv) invasion assays of HeLa cells showed that culturable cells from the different subpopulations do not display the same invasiveness. The results also suggest that newly formed VBNC cells are either weakly able or not able to successfully initiate epithelial cell invasion. Finally, we propose that at entry into the stationary phase, invasiveness may be one way for populations of S. Typhimurium to escape stochastic alteration leading to cell death.

Effect of Agitation on Bacterial Aggregates in Pure Cultures and Raw Milk

1983 ◽  
Vol 46 (8) ◽  
pp. 681-685 ◽  
Author(s):  
ROBYN E. O'CONNOR ◽  
K. N. EWINGS ◽  
NEIL W. HOLLYWOOD
Keyword(s):  
Raw Milk ◽  
Mechanical Agitation ◽  
Filter Technique ◽  
Milk Samples ◽  
Pure Cultures ◽  
Plate Counts ◽  
Bacterial Aggregates ◽  
Direct Epifluorescent Filter Technique ◽  
Clump Size

A comparison of the effects of various mechanical agitation treatments on bacterial aggregates was performed on 8 pure cultures and 27 raw milk samples. Although both syringing and blending produced significant increases in total counts and psychrotroph counts, blending for 2 min gave the greatest increase in count. Use of the direct epifluorescent filter technique (DEFT) confirmed that syringing and blending reduced bacterial clump size to approximately 2 cells. These agitation treatments markedly improved the correlation between DEFT counts and plate counts.

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