Risk Assessment for Cronobacter sakazakii in Powdered Infant Formula


Guidance on Using the Model

Use of the model consists of 5 steps, these steps are:

Step 1:
Define the concentration of C. sakazakii in the powder and specify any sampling plans
Step 2:
Define the Reconstitution Temperature
Step 3:
 Specify Handling and Preparation Scenarios
Step 4:
Set the Baseline
Step 5:
 Run the Model & Obtain Results

Step 1: Define the Concentration of C. sakazakii in the Powder and Specify any Sampling Plans

In Step 1 the contamination level of C. sakazakii in the powdered infant formula must be specified.  The mean concentration of C. sakazakii (in log CFU per gram) and the standard deviation in the concentration, both within a single lot of powder, and between different lots of powder (in log CFU per gram) is required.
In addition, any sampling plan that is to be explored is entered here.  The sampling plan is specified in terms of the number of samples tested from a single lot, and the mass of each sample (in grams).  Up to 4 sampling plans can be compared (in addition to "no plan").

Changes in risk can be explored for the sampling plans and preparation and handling scenarios in isolation or combination. If only sampling plans are to be explored, then go straight to Step 5 (and go straight to “Run the Model and Obtain Results”), and do not enter anything on the pages after "Define Concentration and Sampling Plans". On the results page ignore the results relating to preparation and handling as there is always a default preparation and handling scenario built into the system.

If no sampling plans are to be considered then it is not necessary to enter any plans in the user interface; simply go to Step 2. The model will use the default setting of "No Plan".  This option is always present for sampling plans.

The information entered for Step 1 is used to determine the contamination level in the powder at the end of production.

Step 2: Define the Reconstitution Temperature

In step 2 the temperature of the liquid used to re-hydrate the powder is specified.  At least one temperature must be entered, and up to 5 temperatures can be compared.  Temperatures are entered in ºC.

Step 3:  Specify Preparation and Handling Scenarios

In Step 3 the preparation and handling scenarios are described.  A scenario is entered by first setting the name of the scenario in the box titled “method name”.  At least one scenario must be specified, and up to 5 can be entered.  The specification of a preparation and handling scenario consists of 4 stages: preparation of formula, Holding/cooling, Active rewarming/cooling, and Feeding period.  For each of these processes the duration (in hours), the associated temperature (in °C) and the method of holding is required. Use the Preparation and Handling Guidance for detailed information on completing this section of the model. 

Step 4: Set the Baseline

The baseline reconstitution temperature and preparation and handling scenario must be selected.  The combination of the baseline reconstitution temperature and preparation and handling scenario provides the risk estimate to which all other estimates of risk will be compared to provide estimates of the relative risk reduction.  For more explanation of the use of a baseline to estimate risk click here.

Step 5:  Run the Model & Obtain Results

The final step to using the model is to run the model and view the results.  To run the model simply click the button “Run Model”.  The model will then calculate the results.  Note that this process may take several minutes.  When the model run reaches completion results will be shown.  The baseline scenario will be highlighted in yellow. 

The option is provided to view the results in a report.  Simply click “Create PDF Report” and a pdf file will be displayed, that can be saved or printed if desired (note it may take a minute or more to display the report).  Note that if a printable report is required the intermediate step of clicking "Run Model" can be omitted as creating the report also initiates a model run.  However, the results displayed on the web page will not be updated in this instance.

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