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.

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.

A Bacteriological Survey of Raw Ground Beef1

1977 ◽  
Vol 40 (11) ◽  
pp. 790-794 ◽  
Author(s):  
JAMES F. FOSTER ◽  
JAMES L. FOWLER ◽  
WARREN C. LADIGES
Keyword(s):  
Escherichia Coli ◽  
Microbiological Quality ◽  
Retail Store ◽  
Most Probable Number ◽  
Probable Number ◽  
E Coli ◽  
Fecal Streptococci ◽  
Plate Counts ◽  
Aerobic And Anaerobic

The microbiological quality of 150 units of raw ground beef obtained from a local retail store was determined. The range of aerobic plate counts was from 6.9 × 104 to 8.3 × 107/g. By using the most probable number method 96.7% of the 150 units were positive for coliforms, 94.7% for Escherichia coli and 61.3% for Staphylococcus aureus. By the plate methods, 99.3% of the units were positive for fecal streptococci and 56% were positive for Clostridium perfringens. No salmonellae were isolated. Aerobic and anaerobic organisms were isolated and identified. E. coli was the most frequently isolated aerobe followed by organisms in the Klebsiella-Enterobacter group. Among the anaerobic isolates, C. perfringens was the organism most frequently encountered.

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 Sublethally Injured Escherichia coli O157:H7 ATCC 43895 and Escherichia coli Strain B-41560 Using Selective Agar Overlays versus Commercial Methods

2013 ◽  
Vol 76 (4) ◽  
pp. 674-679 ◽  
Author(s):  
AMANDA R. SMITH ◽  
ALYSHA L. ELLISON ◽  
AMANDA L. ROBINSON ◽  
MARYANNE DRAKE ◽  
SUSAN A. McDOWELL ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Ground Beef ◽  
Food Samples ◽  
Coli Strain ◽  
Milk Formula ◽  
Selective Media ◽  
E Coli ◽  
Infant Milk Formula ◽  
Intervention Measures ◽  
Direct Inoculation

Quality control procedures during food processing may involve direct inoculation of food samples onto appropriate selective media for subsequent enumeration. However, sublethally injured bacteria often fail to grow, enabling them to evade detection and intervention measures and ultimately threaten the health of consumers. This study compares traditional selective and nonselective agar-based overlays versus two commercial systems (Petrifilm and Easygel) for recovery of injured E. coli B-41560 and O157:H7 strains. Bacteria were propagated in tryptic soy broth (TSB), ground beef slurry, and infant milk formula to a density of 106 to 108 CFU/ml and then were stressed for 6 min either in lactic acid (pH 4.5) or heat shocked for 3 min at 60°C. Samples were pour plated in basal layers of either tryptic soy agar (TSA), sorbitol MacConkey agar (SMAC), or violet red bile agar (VRB) and were resuscitated for 4 h prior to addition of agar overlays. Other stressed bacteria were plated directly onto Petrifilm and Easygel. Results indicate that selective and nonselective agar overlays recovered significantly higher numbers (greater than 1 log) of acid-and heat-injured E. coli O157:H7 from TSB, ground beef, and infant milk formula compared with direct plating onto selective media, Petrifilm, or Easygel, while no significant differences among these media combinations were observed for stressed E. coli B-41560. Nonstressed bacteria from TSB and ground beef were also recovered at densities significantly higher in nonselective TSA-TSA and in VRB-VRB and SMAC-SMAC compared with Petrifilm and Easygel. These data underscore the need to implement food safety measures that address sublethally injured pathogens such as E. coli O157:H7 in order to avoid underestimation of true densities for target pathogens.

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.

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.

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.

Prevalence and Amounts of Salmonella Found on Raw California Almonds

2007 ◽  
Vol 70 (4) ◽  
pp. 820-827 ◽  
Author(s):  
MICHELLE D. DANYLUK ◽  
THOMAS M. JONES ◽  
SHIRIN J. ABD ◽  
FRANK SCHLITT-DITTRICH ◽  
MERLE JACOBS ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Risk Assessments ◽  
Most Probable Number ◽  
Probable Number ◽  
Microbial Risk ◽  
E Coli ◽  
Isolation Frequency ◽  
Plate Counts

Data on the prevalence and populations of pathogens in individual foods are critical to the development of product-specific quantitative microbial risk assessments. An outbreak of salmonellosis associated with the consumption of raw almonds in 2000 to 2001 provided an opportunity to evaluate the levels of Salmonella in the recalled product. Duplicate 100-g samples from each of fifty 22.7-kg boxes of recalled almonds were enriched by one of two methods. Salmonella was isolated by at least one method from 42 boxes (84% positive). The levels of Salmonella determined by a three-tube most-probable-number (MPN) method were 8.5 ± 1.3 MPN/100 g. In a subsequent study, raw almonds that arrived at almond processors were sampled from 2001 through 2005 to determine the overall prevalence and levels of Salmonella and to characterize the Salmonella isolates obtained. Aerobic plate counts, coliform counts, and MPN levels of Escherichia coli were also determined on positive samples. An isolation frequency for Salmonella of 81 (0.87% ± 0.2%) of 9,274 samples tested (100 g) was determined for raw almonds sampled from throughout California over the 5-year period. Salmonella was not isolated upon retesting in 59 of 65 positive samples. When detected, levels were 1.2 to 2.9 MPN/100 g. Of the 81 total isolates, 35 different serotypes of Salmonella were represented. Aerobic plate counts, coliform counts, and E. coli levels did not correlate with the presence of Salmonella.

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