Performance Summary
RAPID'B.cereus Method

Introduction
RAPID'B.cereus Agar is a chromogenic medium for thedetection and enumeration of the Bacillus cereus group in foodsamples. The method is based on a chromogenic reaction andphospholipase activity. Typical B. cereus colonies develop acharacteristic red color, generally surrounded with an opaquehalo. The medium’s selective mixture prevents the growthof interfering flora and enables the analysis of a broad rangeof foods. The sensitivity of the medium has been specially
optimized to allow growth of all pathogenic B. cereus strains,even those that are difficult to culture, such as B. cytotoxicus.
The interpretation of RAPID'B.cereus plates is further facilitatedby the high level of contrast between the color of the colonies
and the agar. The RAPID'B.cereus method can be used with
pour-plate or spread-plate inoculation. The RAPID'B.cereus
method has been rigorously tested and validated by aninternationally recognized validation agency (Table 1).

Method Comparison: Relative Trueness
Relative trueness is the degree of agreement between theresults obtained by the reference method and the results
obtained by the RAPID'B.cereus method on identical foodsamples. The following matrices have been tested (Table 3)
and statistically analyzed (Table 4). The statistical analysisof the relative trueness study did not show any difference
between enumeration performed with the RAPID'B.cereus
method and the reference method.
Table 3. Matrices tested with RAPID'B.cereus method.
Category

Matrices Tested

Composite foods
RTRH and RTE, pastries
and egg products

RTRH and RTE: Pasta salad with beans, beef
ravioli with onions, rice salad, tabbouleh, pasta
salad with tomato and mozzarella, ravioli withham, fish pâté, rice with curry, lasagna bolognese
meal, rice-and-bean meal, chicken sandwich,mousse with red fruits, arancini, gratin potatoes,
rice noodle meal, tuna-and-rice salad, pâté,
shepherd’s pie, black wheat crepe, egg blini,stew, stewed vegetables, paella

Table 1. Validations for the RAPID'B.cereus method.
Validation

Certificate Number

NF Validation

BRD 07/26–03/19

Pastries and egg products: Strawberry tart,vanilla éclair, raspberry pastry

Inclusivity/Exclusivity Testing
Inclusivity testing is performed to verify that the method
can detect the B. cereus group (strains listed below), while
exclusivity studies test non–B. cereus group strains to ensure
there is no cross-reactivity. Inclusivity and exclusivity strains
were cultured in Brain Heart Infusion Broth for 24 ± 3 hr at both
30 and 37°C. Decimal dilutions were made and cultured onto
RAPID'B.cereus Agar and incubated at 30 ± 1°C for 24 ± 3 hr.
All colonies were confirmed regardless of morphology. Results
are shown in Table 2.
The following strains were tested in the inclusivity study:
B. cereus		B. pseudomycoides
B. cytotoxicus		
B. thuringiensis
B. mycoides		B. weihenstephanensis

Dairy products
Cheeses
Egg products
Unprocessed, processed

Positives Detected Results

50 B. cereus group strains tested

50/50

100% inclusivity

30 non–B. cereus group strains tested 0/30
(including other 15 Bacillus strains)

100% exclusivity

Unprocessed: Liquid egg yolk, liquid whole egg
Processed: Fresh egg pasta, egg white powder,
egg yolk powder, whole egg powder

Fishery products

Tuna sushi, tuna sashimi, raw salmon, salmon
sushi, salmon sashimi, tuna maki, salmon makiwith avocado, crunchy California roll, salmon
tartare, haddock fillet, cod fillet, salmon terrine,
trout terrine, shrimp, cod with dressing, surimi

Produce

Frozen leeks, frozen peas, frozen carrots

Dried cereals, fruits,nuts, seeds, andvegetables

Oregano, cinnamon, turmeric, cumin, ginger,
coriander, Colombo spice mix (coriander, chili,garlic, and turmeric), dehydrated violet petals,
dehydrated vegetable soup, dehydrated onion
soup, dehydrated leek soup, dehydrated beansoup, dehydrated mashed potatoes, flaked
almonds, muesli, oatmeal, corn flour, driedapricots, dried golden raisins, pea flour, white
rice flour, dry pasta, dry cake mix, quinoa flour,
protein powder, hemp protein, lupin flour, barleyflour, raw bread flour, soybean flour, insect powder,cricket flour, mealworm flour, wheat flour

Infant formula andcereals

Infant formula, infant formula with probiotics,
whey powder, calcium carbonate, lactose protein
starch, maltodextrin, caseinate

Table 2. Results of inclusivity/exclusivity testing.
Strains Tested

Cheeses: Fresh sheep milk cheese, fresh goat milkcheese, fresh cow milk cheese, sheep milk cheesewith rosemary, cow milk cheese with cumin

RTE, ready to eat; RTRH, ready to reheat.

Performance Summary: RAPID'B.cereus Method

Table 4. Statistical analysis of relative trueness.

–CategorySamples Tested

DStandard Deviation

95% Lower Limit

Spread-plate

51

–0.06

0.20

–0.45

0.33

Pour-plate

51

–0.14

0.25

–0.64

0.36

–95% Upper Limit

D, average difference between enumeration of colony forming units (CFU) on RAPID'B.cereus and the reference method in log value.

and high) in each category. Examples of accuracy profiles
are shown in Figure 1. All accuracy profiles were generated
within acceptability limits for both spread- and pour-plate
RAPID'B.cereus methods and all matrices tested.

Infant Formula with Probiotics

Pâté

0.60

0.60

0.40

0.40

0.20

0.20
Bias

Bias

Method Comparison: Accuracy Profile
The accuracy profile study is a comparative study between
the results obtained by the reference method and the resultsof the RAPID'B.cereus method. This study is conducted using
artificially contaminated samples in three levels (low, medium,

0.00
1.00

2.00

3.00

4.00

5.00

0.00
1.00

6.00

–0.20

–0.20

–0.40

–0.40

–0.60

2.00

3.00

4.00

5.00

6.00

–0.60
Reference median

Reference medianFig. 1. Example of accuracy profiles for the RAPID'B.cereus spread-plate method on a dairy and RTE matrix. Bias (); AL, acceptability limit ±0.5 log ().
interval, set at 80% (), β-ETI, expectation tolerance

Visit bio-rad.com/RapidMedia for more information.
BIO-RAD is a trademark of Bio-Rad Laboratories, Inc. All trademarks used herein are the property of their respective owner.

Bio-RadLaboratories, Inc.
Website bio-rad.com USA 1 800 424 6723 Australia 61 2 9914 2800 Austria 00 800 00 24 67 23 Belgium 00 800 00 24 67 23 Brazil 4003 0399
Canada 1 905 364 3435 China 86 21 6169 8500 Czech Republic 00 800 00 24 67 23 Denmark 00 800 00 24 67 23 Finland 00 800 00 24 67 23
France 00 800 00 24 67 23 Germany 00 800 00 24 67 23 Hong Kong 852 2789 3300 Hungary 00 800 00 24 67 23 India 91 124 4029300
Israel 0 3 9636050 Italy 00 800 00 24 67 23 Japan 81 3 6361 7000 Korea 82 2 3473 4460 Luxembourg 00 800 00 24 67 23Mexico 52 555 488 7670 The Netherlands 00 800 00 24 67 23 New Zealand 64 9 415 2280 Norway 00 800 00 24 67 23 Poland 00 800 00 24 67 23Portugal 00 800 00 24 67 23 Russian Federation 00 800 00 24 67 23 Singapore 65 6415 3188 South Africa 00 800 00 24 67 23
Spain 00 800 00 24 67 23 Sweden 00 800 00 24 67 23 Switzerland 00 800 00 24 67 23 Taiwan 886 2 2578 7189 Thailand 66 2 651 8311
United Arab Emirates 36 1 459 6150 United Kingdom 00 800 00 24 67 23

Life ScienceGroup

Bulletin 3261 Ver A

US/EG

21-06170921

Sig 0121