Efficacy of Petrifilm™ VRB for Enumerating Coliforms and Escherichia coli from Frozen Raw Beef

1987 ◽  
Vol 50 (12) ◽  
pp. 1017-1022 ◽  
Author(s):  
LAWRENCE RESTAINO ◽  
RICHARD H. LYON
Keyword(s):  
Escherichia Coli ◽  
Incubation Temperature ◽  
Ground Beef ◽  
Gas Bubbles ◽  
Most Probable Number ◽  
Type I ◽  
Type Ii ◽  
Probable Number ◽  
E Coli ◽  
Colony Diameter

Petrifilm™ violet red bile (PVRB) compared favorably to the most probable number method (MPN) and violet red bile agar (VRBA) methods for enumerating coliforms from frozen raw ground beef. When comparing PVRB and VRBA incubated at 35°C, coliform enumeration displayed a linear relationship (correlation coefficient of 0.932). However, by analyzing 64 ground beef samples, PVRB enumerated 41% more coliforms/g than did VRBA. Two distinct colony types were observed on PVRB: (a) type I (butterfly in appearence) with a colony diameter equal to or greater than 1 mm and gas bubbles 2–4 mm in diameter touching the associated colony; and (b) type II with a colony diameter less than 1 mm in diameter and gas bubbles of the associated colony not necessarily touching the colony but within a colony diameter. The disparity between PVRB and VRBA for enumerating coliforms was attributed to non-coliforms representing approximately 50% of the type II coliform colonies. At 35°C, 83.7% of the type I colonies were Escherichia coli, whereas only 10.9%, of the type II colonies were E. coli. By elevating the incubation temperature from 35°C to 44.5°C, over 90% of the colonies in the counting dilution were type I of which 99.2% were E. coli. At 44.5°C, 39.4% of the type II colonies were E. coli; however, this colony type represented only 9.5% of the total colonies on PVRB. Therefore, a reliable method for enumerating E. coli from raw meat was developed by counting only the type I colonies on PVRB incubated at 44.5°C.

scholarly journals Lessons from a large outbreak of Escherichia coli O157[ratio ]H7 infections: insights into the infectious dose and method of widespread contamination of hamburger patties

1999 ◽  
Vol 122 (2) ◽  
pp. 185-192 ◽  
Author(s):  
J. TUTTLE ◽  
T. GOMEZ ◽  
M. P. DOYLE ◽  
J. G. WELLS ◽  
T. ZHAO ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Ground Beef ◽  
Most Probable Number ◽  
Strong Argument ◽  
Probable Number ◽  
Infectious Dose ◽  
E Coli ◽  
Beef Patties ◽  
Large Outbreak ◽  
Microbiological Testing

Between November 1992 and February 1993, a large outbreak of Escherichia coli O157[ratio ]H7 infections occurred in the western USA and was associated with eating ground beef patties at restaurants of one fast-food chain. Restaurants that were epidemiologically linked with cases served patties produced on two consecutive dates; cultures of recalled ground beef patties produced on those dates yielded E. coli O157[ratio ]H7 strains indistinguishable from those isolated from patients, confirming the vehicle of illness. Seventy-six ground beef patty samples were cultured quantitatively for E. coli O157[ratio ]H7. The median most probable number of organisms was 1·5 per gram (range, <0·3–15) or 67·5 organisms per patty (range, <13·5–675). Correlation of the presence of E. coli O157[ratio ]H7 with other bacterial indicators yielded a significant association between coliform count and the presence of E. coli O157[ratio ]H7 (P=0·04). A meat traceback to investigate possible sources of contamination revealed cattle were probably initially colonized with E. coli O157[ratio ]H7, and that their slaughter caused surface contamination of meat, which once combined with meat from other sources, resulted in a large number of contaminated ground beef patties. Microbiological testing of meat from lots consumed by persons who became ill was suggestive of an infectious dose for E. coli O157[ratio ]H7 of fewer than 700 organisms. These findings present a strong argument for enforcing zero tolerance for this organism in processed food and for markedly decreasing contamination of raw ground beef. Process controls that incorporate microbiological testing of meat may assist these efforts.

Enterobacteriaceae in ground meats

1978 ◽  
Vol 24 (12) ◽  
pp. 1574-1582 ◽  
Author(s):  
Lai-King Ng ◽  
Michael E. Stiles
Keyword(s):  
Ground Beef ◽  
False Positives ◽  
Coliform Bacteria ◽  
Most Probable Number ◽  
Type I ◽  
Enterobacter Agglomerans ◽  
Frozen Ground ◽  
Probable Number ◽  
E Coli ◽  
Solid Media

Presumptive Escherichia coli counts for 312 samples of non-frozen ground beef were determined and compared with proposed Canadian standards. Results for frozen pork sausages, packaged at manufacturer level, indicated little difference in distribution of presumptive E. coli loads compared with retail ground beef. Use of solid media and direct inoculation of EC broth at 45 °C did not give alternative, rapid methods of estimating E. coli loads in ground beef. Counts on violet red bile agar (VRBA) within 18–24 h incubation at 35 °C gave reliable estimates of coliform bacteria (bile-precipitating colonies) and Enterobacteriaceae (total count), with only 1.3 and 10.7% false positives, respectively. Bile-precipitating isolates from VRBA were primarily E. coli, also Serratia liquefaciens, aerogenic Enterobacter agglomerans, Enterobacter cloacae, Citrobacter freundii, and Klebsiella pneumoniae. Non-bile-precipitating colonies were primarily aerogenic E. agglomerans and S. liquefaciens; however, in the most probable number technique E. agglomerans was screened out. In addition to E. coli, E. agglomerans and S. liquefaciens were the principal types of Enterobacteriaceae in these samples. Enterobacter agglomerans gave a variety of IMViC reactions, including the type I (++−−) reaction, whereas S. liquefaciens were predominantly IMViC type −−++. Incubating EC broth at 45.5 °C, as opposed to 44.5 °C, reduced the number of false positives.

Rapid Fluorogenic Enumeration of Escherichia coli in Selected, Naturally Contaminated High Moisture Foods

1987 ◽  
Vol 70 (6) ◽  
pp. 991-993
Author(s):  
Paul L Poelma ◽  
Clyde R Wilson ◽  
Wallace H Andrews
Keyword(s):  
Escherichia Coli ◽  
Ultraviolet Light ◽  
Ground Beef ◽  
Most Probable Number ◽  
High Moisture ◽  
Probable Number ◽  
Pork Sausage ◽  
E Coli

Abstract An assay for the enzyme glucuronidase was used to determine the presence of Escherichia coli in selected, naturally contaminated high moisture foods. Raw pork sausage, ground turkey, and ground beef were inoculated into tubes containing the substrate 4-methylumbelliferyl beta-D-glucuronide (MUG) in lauryl tryptose (LT) medium. After incubation at 35°C for 24 h, the inoculated LT-MUG tubes were examined under longwave ultraviolet light for the presence of a fluorogenic glucuronidase end product. A fluorescing tube indicated the presumptive presence of E. coli. The 10 day most probable number method of the AOAC and the LT-MUG procedure gave comparable recoveries of E. coli.

Comparison of the Traditional Three-Tube Most Probable Number Method with the Petrifilm, SimPlate, BioSys Optical, and Bactometer Conductance Methods for Enumerating Escherichia coli from Chicken Carcasses and Ground Beef

2000 ◽  
Vol 63 (9) ◽  
pp. 1179-1183 ◽  
Author(s):  
SCOTT M. RUSSELL
Keyword(s):  
Escherichia Coli ◽  
Correlation Coefficients ◽  
Ground Beef ◽  
Foodborne Illness ◽  
Most Probable Number ◽  
Probable Number ◽  
Rapid Methods ◽  
E Coli ◽  
Microbiological Methods ◽  
The Cost

A study was conducted to compare commonly used methods, such as Petrifilm and SimPlate, and the rapid microbiological methods BioSys optical and Bactometer conductance to the standard most probable number (MPN) procedure for enumerating Escherichia coli from poultry carcasses and ground beef. Broiler carcasses and ground beef were evaluated in each of three replicate trials. Five groups of carcasses or ground beef were sampled and analyzed using Petrifilm, SimPlate, BioSys optical, and Bactometer conductance measurements after temperature abuse at 37°C for 0 (Petrifilm and SimPlate only), 2, 4, 6, or 8 h. The correlation coefficients for the regression lines comparing the standard E. coli MPN procedure to Petrifilm and SimPlate for chicken and ground beef, respectively, were as follows: 0.95, 0.94, 0.93, and 0.91. The correlation coefficients for the regression lines comparing the standard E. coli MPN procedure to BioSys optical and Bactometer conductance measurements for chicken and ground beef, respectively, were −0.91, −0.90, −0.93, and −0.96. Although Petrifilm and SimPlate performed well, E. coli could not be enumerated from 16.7 and 10% of samples, respectively, using these methods. The BioSys optical and Bactometer conductance methods performed very well when compared with Petrifilm and SimPlate. Using rapid methods (BioSys optical and Bactometer conductance), results were obtained in 1 to 11 h rather than the 48 h required to conduct Petrifilm or SimPlate or the 5 days required to conduct the MPN procedure. These methods may allow processors to test products and obtain results before shipping, avoiding the cost and loss of reputation associated with a recall or foodborne illness outbreak.

Enumeration of Escherichia coli O157:H7 in Outbreak-Associated Beef Patties

2016 ◽  
Vol 79 (7) ◽  
pp. 1266-1268 ◽  
Author(s):  
ALEXANDER GILL ◽  
GEORGE HUSZCZYNSKI
Keyword(s):  
Escherichia Coli ◽  
Ground Beef ◽  
Most Probable Number ◽  
Escherichia Coli O157 ◽  
Cross Contamination ◽  
Probable Number ◽  
E Coli ◽  
Beef Patties ◽  
Selective Agar ◽  
Agar Media

ABSTRACT An outbreak of five cases of Escherichia coli O157 infection that occurred in Canada in 2012 was linked to frozen beef patties seasoned with garlic and peppercorn. Unopened retail packs of beef patties from the implicated production lot were recovered and analyzed to enumerate E. coli O157, other E. coli strains, and total coliforms. E. coli O157 was not recovered by direct enumeration on selective agar media. E. coli O157 in the samples was estimated at 3.1 most probable number per 140 g of beef patty, other E. coli was 11 CFU/g, and coliforms were 120 CFU/g. These results indicate that the presence of E. coli O157 in ground beef at levels below 0.1 CFU/g may cause outbreaks. However, the roles of temperature abuse, undercooking, and cross-contamination in amplifying the risk are unknown.

Comparison of Methods for Estimation of Coliforms, Fecal Coliforms and Enterococci in Retail Ground Beef

1978 ◽  
Vol 41 (4) ◽  
pp. 263-266 ◽  
Author(s):  
C. J. PIERSON ◽  
B. S. EMSWILER ◽  
A. W. KOTULA
Keyword(s):  
Escherichia Coli ◽  
Brilliant Green ◽  
Agar Medium ◽  
Ground Beef ◽  
Fecal Coliforms ◽  
Most Probable Number ◽  
Type I ◽  
Lauryl Sulfate ◽  
Comparison Of Methods ◽  
Probable Number

Seven recommended methods for estimation of coliforms, three for fecal coliforms and four for enterococci were tested on 30 retail ground beef samples. Lauryl sulfate tryptose broth gave higher coliform counts than did MacConkey's broth or brilliant green lactose bile broth 2% in 3-tube Most Probable Number (MPN) methods. With all MPN broths, coliforms counts were significantly (P ⩽0.05) higher after 48 than after 24 h of incubation. Presumptive coliform counts were higher with surface-overlay plating on violet red bile agar than with pour plating on the same agar or with the MPN broths. However, presence of Escherichia coli Type I was not confirmed as often from the agar medium as the broths. For estimation of fecal coliforms, counts did not differ significantly (P ⩽0.05) between EC broth (45.5 C) and brilliant green lactose bile broth 2% (44 C). Enterococci counts varied significantly (P ⩽0.05) among the four methods.

Reliability of Escherichia coli Counts for Vacuum-Packaged Ground Beef

1992 ◽  
Vol 55 (4) ◽  
pp. 266-270 ◽  
Author(s):  
L. J. HARRIS ◽  
M. E. STILES
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Ground Beef ◽  
Most Probable Number ◽  
Probable Number ◽  
Selective Media ◽  
E Coli ◽  
Direct Inoculation ◽  
Plate Counts ◽  
Selective Plating

Test strains of Escherichia coli were inoculated into fresh ground beef that had been irradiated or carefully excised and aseptically ground. Samples were vacuum-packaged and stored at 4°C. Plate counts on selective media incubated at 35 or 45°C were highly consistent during the 7- to 20-d storage periods. The standard most probable number (MPN) technique (lauryl tryptose broth at 35°C, followed by EC broth at 45°C) was also reliable. In contrast, direct inoculation into broths incubated at 45°C gave unreliable and highly variable results. The cause of the variability of the MPN counts at 45°C could not be determined. It was not due to lactic acid bacteria growing in the ground beef. E. coli in refrigerated, vacuum-packaged ground beef can be reliably detected by direct inoculation of selective plating media incubated at 45 °C. Direct inoculation of selective broth media for the MPN technique at 45°C is not recommended.

Use of the Chromogenic Substrate 5-Bromo-4-Chloro-3-Indolyl-B-D-Glucuronide (X-GLUC) for Enumerating Escherichia coli in 24 H from Ground Beef

1990 ◽  
Vol 53 (6) ◽  
pp. 508-510 ◽  
Author(s):  
LAWRENCE RESTAINO ◽  
ELON W. FRAMPTON ◽  
RICHARD H. LYON
Keyword(s):  
Escherichia Coli ◽  
Ground Beef ◽  
Most Probable Number ◽  
Chromogenic Substrate ◽  
Probable Number ◽  
E Coli ◽  
Glucuronidase Activity ◽  
Significant Difference ◽  
Plating Method ◽  
Positive Linear Correlation

A 24-h direct plating method for Escherichia coli using the chromogenic substrate 5-bromo-4-chloro-3-indolyl-B-D-glucuronide (X-GLUC) incorporated into a Peptone-tergitol agar base (PTX) was compared with the standard 3-tube Most Probable Number (MPN) method on 50 naturally contaminated ground beef samples. A paired-comparisons t-test showed no significant difference between the two methods. A positive linear correlation between the two methods was observed over the entire range of values. Ninety-seven percent of the positive colonies (blue colonies) on PTX agar were indentified as E. coli, whereas no atypical colonies (nonblue) were characterized as such. Thus, a simple and reliable enumeration of E. coli can be made within 24 h using the X-GLUC substrate in a selective agar as an indicator of B-glucuronidase activity.

Comparison of β-Glucuronidase and Indole-Based Direct Plating Methods for Enumerating Escherichia coli in Artificially Inoculated Ground Meats

1990 ◽  
Vol 53 (11) ◽  
pp. 933-935 ◽  
Author(s):  
ELON W. FRAMPTON ◽  
LAWRENCE RESTAINO ◽  
NANCY BLASZKO
Keyword(s):  
Escherichia Coli ◽  
Ground Beef ◽  
Plate Count ◽  
Most Probable Number ◽  
Probable Number ◽  
E Coli ◽  
Glucuronidase Activity ◽  
Plate Count Agar ◽  
Significant Difference ◽  
Indole Production

Peptone tergitol glucuronide (PTG) agar containing 4-methylumbelliferyl-β-D glucuronide (MUG) (for β-glucuronidase activity), the Holbrook, Anderson, Baird-Parker (HABP) method (for detecting indole production), and the standard 3-tube most probable number (MPN) method were compared with plate count agar (PCA) for enumerating three strains of unstressed Escherichia coli artificially inoculated into ground beef and chicken at 1–6 × 106 cells/g. No significant difference (P&gt;0.05) was determined between PTG agar and PCA in the recovery of E. coli. The MPN method enumerated a significantly greater (P&lt;0.05) number of E. coli cells than PCA. Compared with PCA, the HABP method recovered a significantly lower (P&lt;0.05) number of E. coli cells from chicken, whereas no significant difference (P&gt;0.05) was obtained with ground beef. When combining all data from chicken and beef, the recovery of E. coli cells by the HABP method was also significantly lower (P&lt;0.05). Overall, based on the enumeration of E. coli on PCA, the HABP method, PTG agar, and MPN method recovered 57, 102, and 144%, respectively.

scholarly journals Biochemical and structural characterization of the novel sialic acid-binding site of Escherichia coli heat-labile enterotoxin LT-IIb

2016 ◽  
Vol 473 (21) ◽  
pp. 3923-3936 ◽  
Author(s):  
Dani Zalem ◽  
João P. Ribeiro ◽  
Annabelle Varrot ◽  
Michael Lebens ◽  
Anne Imberty ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Binding Site ◽  
Cholera Toxin ◽  
Carbohydrate Binding ◽  
Type I ◽  
Type Ii ◽  
E Coli ◽  
B Subunit ◽  
Heat Labile ◽  
B Subunits

The structurally related AB5-type heat-labile enterotoxins of Escherichia coli and Vibrio cholerae are classified into two major types. The type I group includes cholera toxin (CT) and E. coli LT-I, whereas the type II subfamily comprises LT-IIa, LT-IIb and LT-IIc. The carbohydrate-binding specificities of LT-IIa, LT-IIb and LT-IIc are distinctive from those of cholera toxin and E. coli LT-I. Whereas CT and LT-I bind primarily to the GM1 ganglioside, LT-IIa binds to gangliosides GD1a, GD1b and GM1, LT-IIb binds to the GD1a and GT1b gangliosides, and LT-IIc binds to GM1, GM2, GM3 and GD1a. These previous studies of the binding properties of type II B-subunits have been focused on ganglio core chain gangliosides. To further define the carbohydrate binding specificity of LT-IIb B-subunits, we have investigated its binding to a collection of gangliosides and non-acid glycosphingolipids with different core chains. A high-affinity binding of LT-IIb B-subunits to gangliosides with a neolacto core chain, such as Neu5Gcα3- and Neu5Acα3-neolactohexaosylceramide, and Neu5Gcα3- and Neu5Acα3-neolactooctaosylceramide was detected. An LT-IIb-binding ganglioside was isolated from human small intestine and characterized as Neu5Acα3-neolactohexaosylceramide. The crystal structure of the B-subunit of LT-IIb with the pentasaccharide moiety of Neu5Acα3-neolactotetraosylceramide (Neu5Ac-nLT: Neu5Acα3Galβ4GlcNAcβ3Galβ4Glc) was determined providing the first information for a sialic-binding site in this subfamily, with clear differences from that of CT and LT-I.

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