EAL

MHFS: Food Safety (2012-2013)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To report outbreaks of salmonellosis and the evolution of subsequent actions taken by industry and federal regulators to prevent further illness due to raw, frozen, microwaveable, breaded, pre-browned and stuffed chicken products.

Inclusion Criteria:

All Minnesota residents with a culture-confirmed Salmonella infection are routinely interviewed by MDH staff with a standard questionnaire about symptom history, food consumption and other potential exposures occurring the seven days prior to onset of illness.

Exclusion Criteria:

Not described.

Description of Study Protocol:

Recruitment

All Minnesota residents with a culture-confirmed Salmonella infection are interviewed by MDH staff with a standard questionnaire about symptom history, food consumption and other potential exposures occurring in the seven days prior to onset of illness.

Design

Case studies.

Statistical Analysis

All descriptive and analyses for these investigations were conducted using EpiInfo version 6.04d.

Data Collection Summary:

Timing of Measurements

Minnesota residents with a culture-confirmed case of Salmonella infection were interviewed by MDH staff with a standard questionnaire about symptom history, food consumption and other potential exposures occurring in the seven days prior to illness onset.

Dependent Variables

Symptom history, food consumption and other potential exposures occurring in the seven days prior to illness onset
The questionnaire contains detailed food exposure questions, including open-ended food histories and objective yes/no questions about numerous specific food items as well as brand names and purchase locations.

Independent Variables

Outbreaks due to frozen, microwaveable, pre-browned and stuffed chicken products:

In each investigation, intact frozen chicken products were collected from confirmed case households and retail stores, then cultured for Salmonella either at MDH or the Minnesota Department of Agriculture
100g of product was placed into 900ml of lactose broth and blended or ground for two minutes. After one hour at room temperature, the pH was measured and adjusted to 6.8 if necessary.
Clinical laboratories are required to forward all Salmonella isolates to the MDH Public Health Laboratory for confirmation and PFGE sub-typing
Pulsed-field gel electrophoresis (PFGE) sub-typing after digestion with the enzyme Xhal is conducted on all isolates as soon as they are submitted
Samples screened as positive were plated out and identified for the following Bacteriological Analytical Manual procedure for Salmonella.

Description of Actual Data Sample:

Initial N

Four outbreaks of salmonellosis were identified in Minnesota from 1998 through 2006:

1998: 33 Salmonella Typhimurium cases associated with chicken kiev
2005: Four Salmonella Heidelberg cases associated with chicken broccoli and cheese
2005-2006: 27 Salmonella Enteritidis cases associated with multiple product varieties
2006: Three Salmonella Typhimurium cases associated with chicken broccoli and cheese

Age

Median age of cases was 17 years (range one to 78 years).

Location

Minnesota Department of Public Health, Minnesota.

Summary of Results:

Key Findings

Most case patients thought that the breaded and pre-browned product was precooked, and most cooked the product in a microwave oven but did not follow the package cooking instructions (turning the product over, using a shorter cooking time than recommended and using a microwave with less than the recommended 800 watts)
None of the cases used an internal temperature of the product after cooking
Similar to previous salmonellosis outbreaks associated with raw, breaded chicken nuggets or strips in Canada and Australia, inadequate labeling, consumer responses to labeling and microwave cooking were key factors in the occurrence of the outbreaks
Modification of labels, verification of cooking instructions by the manufacturer and notifications to alert the public that these products contain raw poultry, implemented due to the first two outbreaks, did not prevent further outbreaks.

Author Conclusion:

Microwave cooking is not recommended as a preparation method for raw, frozen, breaded, pre-browned and stuffed chicken products unless they are pre-cooked or irradiated prior to sale.

Funding Source:

Government:

Center for Disease Control and Prevention

Reviewer Comments:

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	N/A
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	N/A

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	Yes
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	Yes
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		N/A
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		No
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	No
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	No
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	No
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	No
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes