Evaluation of a rapid fluorogenic method for the detection ofEscherichia coliin dairy products

1991 ◽  
Vol 58 (4) ◽  
pp. 477-483 ◽  
Author(s):  
Hassan R. Sarhan ◽  
Leslie R. Williams ◽  
Howard A. Foster
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Dairy Products ◽  
Membrane Filtration ◽  
False Negative ◽  
Raw Milk ◽  
False Positive Reaction ◽  
Negative Results ◽  
False Negative Results ◽  
Soft Cheese

SummaryA rapid fluorogenic medium was evaluated for the detection ofEscherichia coliin dairy products. The medium was capable of detectingEsch. coliafter 7·5 h incubation at 41·5 °C. Samples of pasteurized milk (136), raw milk (63), soft cheese (60) and pasteurized cream (39) were examined with media based on 4-methylumbelliferyl-β-D-glucuronide (MUG-7) and Violet red bile agar and there were no significant differences between the numbers ofEsch. colidetected on the two media. MUG-7 medium had a specificity of 98·6% and the small number of organisms giving a false positive reaction were identified asKlebsiella pneumoniae. The incidence of false negative results was ∼2%. MUG-7 medium was suitable for pour plate, spread plate and membrane filtration methods. Possible applications of the method are discussed.

Be aware of Shiga-toxin 2f-producing Escherichia coli: case report and false-negative results with certain rapid molecular panels

2020 ◽  
Vol 98 (4) ◽  
pp. 115177
Author(s):  
Aurélie Cointe ◽  
André Birgy ◽  
Alice Pascault ◽  
Ferielle Louillet ◽  
Alice Dufougeray ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Case Report ◽  
Shiga Toxin ◽  
False Negative ◽  
Negative Results ◽  
False Negative Results

Utilization of Fluorogenic Assay for Rapid Detection of Escherichia coli in Acidic Fruit Juice

2002 ◽  
Vol 65 (12) ◽  
pp. 1943-1948 ◽  
Author(s):  
STEVEN PAO ◽  
CRAIG L. DAVIS ◽  
LORETTA M. FRIEDRICH ◽  
MICKEY E. PARISH
Keyword(s):  
Escherichia Coli ◽  
Fruit Juice ◽  
Uv Light ◽  
False Negative ◽  
Enzyme Reaction ◽  
Inhibitory Effect ◽  
Sample Sizes ◽  
Citrus Juice ◽  
Negative Results ◽  
False Negative Results

This study was undertaken to investigate interference by acids commonly found in fruit juice in Escherichia coli assays involving the use of 4-methylumbelliferyl-β-d-glucuronide (MUG) as a fluorogenic substrate for enzyme reaction. Fluorescence intensity was negatively correlated (P < 0.001) with the volume of fresh citrus juice tested by the lauryl tryptose broth (LST)-MUG assay, and the permissible sample sizes were limited to 0.3 and 0.5 ml for fresh citrus juices with pHs of 3.3 and 3.9, respectively. In addition, false-negative results were visually observed under UV light when the E*Colite assay was used to test large volumes (5 to 10 ml per test) of fresh citrus juice or when the test broth used for the LST-MUG assay was supplemented with citric, malic, or tartaric acid at 2 to 4 g/liter. These results suggest that the size and pH of acidic samples should be controlled in MUG-based fluorogenic assays. The inhibitory effect on fluorescence was due to high acidity, which reduces fluorescence from 4-methylumbelliferone. Buffering improved the assays. When sodium bicarbonate was incorporated in the enrichment broth at 10 g/liter, the permissible sample sizes for fresh grapefruit juice (pH 3.1) increased from 0.3 to 1 ml for the LST-MUG (with 9.9 ml of broth) assay and from 3 to 10 ml for the E*Colite (with 99 ml of broth) assay.

Spatial Distribution of Salmonella, Escherichia coli O157:H7, and Other Bacterial Populations in Commercial and Laboratory-Scale Sprouting Mung Bean Beds

2005 ◽  
Vol 68 (12) ◽  
pp. 2510-2518 ◽  
Author(s):  
R. HORA ◽  
M. KUMAR ◽  
L. GARCIA ◽  
B. SCHUMACHER ◽  
J. ODUMERU ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Irrigation Water ◽  
Water Samples ◽  
Mung Bean ◽  
False Negative ◽  
Bacterial Populations ◽  
Negative Results ◽  
False Negative Results ◽  
Thermotolerant Coliforms ◽  
Microbiological Status

The reliability of testing spent irrigation water to assess the microbiological status of sprouting mung bean beds has been investigated. In commercial trials, the distribution of opportunistic contaminants within 32 bean sprout beds (25 kg of mung beans per bin) was assessed 48 h after germination. The prevalence of generic Escherichia coli, thermotolerant coliforms, and Aeromonas in sprouts (n = 288) was 5, 11, and 39%, respectively, and 57, 70, and 79% in the corresponding spent irrigation water samples (n = 96). Contamination was heterogeneously distributed within the seedbed. In laboratory trials, beans inoculated with a five-strain cocktail of either Salmonella or E. coli O157:H7 (103 to 104 CFU/g) were introduced (1 g/500 g of noninoculated seeds) at defined locations (top, middle, or base), and the beans were then sprouted for 48 h. When seeds inoculated with pathogens were introduced at the base or top of the seedbed, the pathogens were typically restricted to these sites and resulted in 44% of the spent irrigation water samples returning false-negative results. Introducing inoculated beans into the middle or at the presoak stage enhanced the distribution of both pathogens within the subsequent sprout bed and resulted in comparable levels recovered in spent irrigation water. The study demonstrated that even though screening a single sample of spent irrigation water is more reliable than testing sprouts directly, it does not provide an accurate assessment of the microbiological status of sprouting mung bean beds. Such limitations may be addressed by ensuring that bean batches are mixed prior to use and by taking spent irrigation water samples from multiple sites at the latter stages of the sprouting process.

Comparison of Enrichment Conditions for Rapid Detection of Low Numbers of Sublethally Injured Escherichia coli O157in Food

2009 ◽  
Vol 72 (9) ◽  
pp. 1862-1868 ◽  
Author(s):  
VICKY JASSON ◽  
ANDREJA RAJKOVIC ◽  
LEEN BAERT ◽  
JOHAN DEBEVERE ◽  
MIEKE UYTTENDAELE
Keyword(s):  
Escherichia Coli ◽  
Bile Salts ◽  
False Negative ◽  
Raw Milk ◽  
Detection Methods ◽  
Fermented Sausage ◽  
E Coli ◽  
Negative Results ◽  
Peptone Water ◽  
Sprouted Seeds

A comparative study of lag phases and growth rates of healthy, stressed, and sublethally injured Escherichia coli O157 cells in 10 enrichment broths was performed. The evaluation of enrichment protocols was validated by different end point detection methods (two PCR and two combined capture-plate methods). Tryptic soy broth b [TSB (b)] provided the fastest growth (μmax = 1.00 ± 0.06 h−1) but failed to recover oxidative-stressed E. coli O157. TSB (a), TSB–yeast extract medium, TSB supplemented with 8 mg/liter novobiocin plus 16 mg/liter vancomycin (TSB+), buffered peptone water (BPW), and BPW supplemented with 8 mg/liter vancomycin (BPW+V) enabled resuscitation of E. coli O157 cells independent from precultural conditions. Modified TSB plus 10 mg/liter novobiocin (mTSB+N), EC medium, EC reduced bile salts medium (ECred), TSB (b), and TSB supplemented with 8 mg/liter novobiocin plus 16 mg/liter vancomycin plus 2 mg/liter rifampin plus 1 mg/liter K-Telluriet plus 1.5 g/liter bile salts no. 3 (TSB++) all failed to recover E. coli O157 cells for at least one type of stress. The use of TSB (a), TSB+, BPW, and BPW+V was compared with that of mTSB+N (International Organization for Standardization reference broth) for reliable detection of low numbers of healthy, stressed, and sublethally injured E. coli O157 (approximately 10 CFU/10 g) from foods (sprouted seeds, fermented sausage, raw milk, and raw ground beef). When low numbers of healthy cells were inoculated, BPW, BPW+V, TSB, TSB+, and mTSB+N enabled growth until detectable numbers within 6 h of enrichment at 41.5°C. Results showed that mTSB+N failed to recover to detectable numbers E. coli O157 cells sublethally injured by freeze and food stresses, in contrast to what was obtained with BPW and BPW+V. This study highlights that using mTSB+N for recovery of E. coli O157 from foods may yield false-negative results.

Comparative Evaluation of Practical Functionality of Rapid Test Format Kits for Detection of Escherichia coli O157:H7 on Lettuce and Leafy Greens

2009 ◽  
Vol 72 (12) ◽  
pp. 2461-2470 ◽  
Author(s):  
C. B. D'LIMA ◽  
T. V. SUSLOW
Keyword(s):  
Escherichia Coli ◽  
False Negative ◽  
Rapid Test ◽  
Leafy Vegetables ◽  
Critical Threshold ◽  
Escherichia Coli O157 ◽  
Leafy Greens ◽  
Negative Results ◽  
Consumer Safety ◽  
False Negative Results

Multistate outbreaks of Escherichia coli O157:H7 infection in 2005 and 2006 associated with fresh and especially minimally processed produce greatly escalated the application of rapid pathogen detection systems to safety management in this food category. Pathogen testing was rapidly integrated into preharvest qualification for field lots, incoming raw produce, or final product. The raw produce and final product were incorporated into test-and-hold programs, typically within a 10-h time frame. To enhance consumer safety and provide guidance for the industry, an assessment of selected kits in comparison to a culture-based method was undertaken. Four primary kits were compared: the Neogen Reveal, SDI RapidChek, BioControl GDS O157, and Qualicon BAX O157 MP. Nine different leafy greens were freshly harvested and inoculated with a five-isolate mixture of E. coli O157:H7 at 10 CFU/25 g of sample, and cultures were enriched following the specified protocol. The PCR method was most consistent for identifying the presence of the inoculated pathogen in the shortest period of time. For the red-pigmented leafy vegetables red butter lettuce, curly endive, red lettuce, and lollo rosa, 13, 38, 88, and 100% false-negative results, respectively, were obtained with the immunoassays, but PCR detection was minimally affected. Immunoassays were negatively affected by delays in achieving critical threshold populations during the allowed enrichment period. Leafy green type, temperature abuse, and preharvest environment were unlikely to affect the results of PCR-based kits. Findings strongly suggest that product testing systems using 8-h detection cutoffs may give false-negative results. These issues become very important in high-throughput testing and retest protocols for presumptive pathogen-positive lots of produce.

Multilaboratory Validation of a Luminex Microbead-Based Suspension Array for the Identification of the 11 Most Clinically Relevant Shiga Toxin–Producing Escherichia coli O Serogroups†

2013 ◽  
Vol 76 (5) ◽  
pp. 867-870 ◽  
Author(s):  
ANDREW LIN ◽  
JULIE A. KASE ◽  
MICHELLE M. MOORE ◽  
INSOOK SON ◽  
NELLY TRAN ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
High Throughput ◽  
Shiga Toxin ◽  
False Positive ◽  
Collaborative Study ◽  
False Negative ◽  
Robust Method ◽  
Suspension Array ◽  
Negative Results ◽  
False Negative Results

Rapid and high-throughput identification and serotyping of Shiga toxin–producing Escherichia coli (STEC) O serogroups is important for detecting, investigating, and controlling STEC infection outbreaks and removing hazardous products from commerce. A Luminex microbead-based suspension array has been developed to identify the 11 most clinically relevant STEC serogroups: O26, O45, O91, O103, O104, O111, O113, O121, O128, O145, and O157. Here we present results of a blinded multilaboratory collaborative study involving 10 participants from nine laboratories using 55 unknown strains. From the total 495 analyses, two false-positive and three false-negative results were obtained, indicating the assay to be a rapid, high-throughput, and robust method for identifying clinically relevant STEC serogroups.

scholarly journals A comparison of confirmatory media for coliform organisms and Escherichia coli in water

1981 ◽  
Vol 87 (3) ◽  
pp. 369-375 ◽  
Keyword(s):  
Escherichia Coli ◽  
Brilliant Green ◽  
False Negative ◽  
Gas Production ◽  
Single Tube ◽  
Negative Results ◽  
False Negative Results ◽  
Indole Production

SummaryGas production by coliform organisms and Escherichia coli from lauryl tryptose lactose broth (LTLB) was compared with that from brilliant green (lactose) bile broth (BGB). These media were compared with lauryl tryptose mannitol broth (LTMB) with and without added tryptophan for both gas and indole production. At 37 °C, LTLB and BGB were both satisfactory for gas production, but at 44 °C, LTLB gave fewer false-negative results and was thus significantly less inhibitory than BGB. However when LTLB and LTMB were compared as single-tube confirmatory media, LTLB give a high proportion of false-negative reactions in the indole test at 44 °C. The substitution of mannitol for lactose and the addition of tryptophan yielded a satisfactory medium for both confirmation of gas production and the demonstration of indole at 44 °C.

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