# Presentation: 228076

## UPDATE: Assessment of the Relative Risk to Public Health from Foodborne Listeria monocytogenes Among Selected Categories of Ready-to-Eat Foods

**Robert L. Buchanan **
**Sherri Dennis**
**Richard C. Whiting**
**U.S. DHHS FDA CFSAN**

## The Listeria “Problem”

**Improve public health by determining which foods should receive the most regulatory attention**

## FDA/FSIS Draft L. monocytogenes Risk Assessment – Jan 2001

**Carried out in a manner consistent with the guidelines established by Codex Alimentarius, NACMCF, and ICMSF for the conduct of a microbial risk assessment:**
**Transparency**
**Broad scientific and stakeholder input**
**Extensive peer review**

## Sources and Types of Data

**Consumption surveys**
**Contamination data **
**Growth, survival and thermal inactivation data -- refrigeration, storage and cooking/reheating **
**Animal studies -- virulence of Lm strains and susceptibility in subpopulations**
**Epidemiological investigations/listeriosis surveillance**

## Selection of Food Categories

**Potential for Lm Contamination**
**Ready-to-eat (with one exception, foods cooked just prior to consumption not included)**
**History of causing listeriosis**
**Food contamination and consumption data**
**Individual foods grouped into categories**

## Exposure Assessment

**Number of *****L. monocytogenes***** ingested**
**Frequency of contamination of food**
**Extent of contamination**
**Growth before consumption**
**Frequency that food is consumed**
**Amount of food consumed at a serving**

## Exposure Assessment

**Additional variables considered to determine the amount of *****L. monocytogenes***** consumed**
**Home refrigerator temperatures**
**Percent of frankfurters reheated**
**Effect of temperature on growth rate**
**Effect of temperature on extent of growth**

## Hazard Characterization

**Probability of illness/mortality as a function of number of *****L. monocytogenes***** ingested**
**Dose-response curve “shape” from mice**
**Variation in virulence of *****L. monocytogenes***** isolates**
**Accounting for differences in susceptibility of mice and men - “anchor to health statistics”**
**Variation in susceptibility within age groups**
**Variation in susceptibility between age groups **

## Populations Studied

**Perinatal:**** ****16 weeks after fertilization to 30 days after birth**** **
**Elderly:**** ****60 or more years of age**
**Intermediate-age:**** ****General population less than 60 years old, includes healthy people and people more susceptible to listeriosis**

## Risk Characterization

**Combine exposure assessment and hazard characterization**
**Frequency of death (mortality)**
**Convert to severe cases of listeriosis by multiplying by 5**
**Characterize variability and uncertainty**

## Risk Characterization

**Number of Lm consumed per serving**

**Mortality cases per serving**

**Dose -response model (mortality)**

**Listeriosis cases per annum**

**Listeriosis cases per serving**

**Frequency of servings**

**+**

**Exposure assessment**

**Hazard characterization**

**X 5**

**X 5**

- [30,000 + 300] iterations

**Repeat 4,000 times!**

**Notes:**
Title needs to be changed to me more descriptive.  Are you referring to Risk Characterization Modeling?

## Risk Characterization

**Examined results in light of:**
**Quantitative results**
**Data variability**
**Model uncertainty**
**Consideration of qualitative factors**
**Epidemiological history**
**Food characteristics**
**Extensive discussion of each food category**

## Initial (2001) Risk Ranking--Per Serving

## Listeriosis: Predicted Relative Risk per Serving–Total Population (2001) 

**Notes:**
Relative Risk!

## Initial (2001) Risk Ranking - Per Annum 

## Listeriosis: Predicted Relative Risk per Annum – Total Population (2001)

**0**

**200**

**400**

**600**

**800**

**1000**

**1200**

**1400**

**1600**

**Median Cases per Annum**

- DM

- PM

- DS

- FF

- MD

- SS

- P

- FS

- CR

- PC

- V

- DFS

- PF

- F

- SC

- UM

- RS

- GC

- AC

- IC

## Initial (2001) Conclusions and Interpretation

**Broad themes reemphasized:**
**Disease primarily impacts specific “at-risk” subpopulations**
**Disease is rare but severe**
**Substantial difference in risk among different food categories**

## Initial (2001) Conclusions and Interpretation

**Major factors that affect risk:**
**Amount and frequency of consumption**
**Frequency and levels of contamination**
**Ability of food to support growth**
**Refrigerated storage temperature**
**Refrigerated storage time**

## Technical and Scientific Reviews of the FDA/FSIS Risk Assessment

## Process For Finalizing FDA/FSIS LM Risk Assessment

**Draft RA for public comment (Jan 2001)**
**Public comment period closes (July 2001)**
**Review comments and newly available data**
**Develop changes to the model**
**Develop revised document**
**Internal review and approval**
**Issue revised risk assessment and model (planned June/July 2003)**
**Public meeting (TBA)**
**Future updates of LM RA (as needed)**

## Public comments

**Submissions to the docket represented**** **
**Consumer groups, industry, trade associations, expert modelers, manufacturers of food processing equipment, food retailers, marketers for food producers/ processors, and education/scientific societies**

## Public Comments

**Revise food categories**
**Reorganize cheeses according to percentage moisture**
**Split frankfurters into two separate categories (reheated and not reheated)**
**Move vegetable and fruit salads to deli salads food category**
**Weight contamination data according to geographic location, year collected, study size**

## Some of the New Data 

**AMI survey**
**Home storage of deli meats and frankfurters**
**Example: Average storage time for pre-packaged deli meats and hot dogs:**
**1 to 3 days (32%)**
**4 to 7 days (37%)**
**8 to 10 days (6%)**
**11 to 14 days (4%)**
**Don’t eat these foods (13%)**

## Some of the New Data (2)

**NFPA retail study**
**Frequency and prevalence of LM in deli meats, deli salads, vegetable salads, seafood salads, smoked seafood, soft cheese, and Hispanic-style cheese**
**Total samples: 31705 tested (MD and CA) **
_**Example:  Deli Meats**_**  **
**9,199 tested: 82 positive (0.9%)**
**1 sample 10****3**** to 10****4 ****cfu/g**
**7 samples 100-1000 cfu/g**
**2 samples 10-100 cfu/g**
**10 samples >1-10 cfu/g**
**20 samples >0.1 –1 cfu/g**
**42 samples 0.04 – 0.1 cfu/g**
**Pre-packed: 77% of the samples (0.4%) **
**Deli-packed: 23% of the samples (2.7%)**

## Dose-Response Changes 

**Separate mortality to hospitalization ratios  calculated for each population**
**An additional year of FoodNet data (2000) was included (slightly reduced the total number of predicted cases)**
**Scaling factor was selected to adjust the median value for the predicted number of cases to the FoodNet estimates**** **
**A different scaling factor is used to adjust the exposure assessment to the FoodNet estimates. **
**As a result, the scaling factor is a distribution; the total number of predicted cases is not.**

## Comparison of DR 2001 and Revised –Elderly Population

**2001**

**Revised**

## Comparison of 2001 and Revised Results – Deli meats, Elderly

| Listeriosis | Median | 5th ‘ile | 95th ‘ile |
| --- | --- | --- | --- |
| Per annum |  |  |  |
| 2001 | 650 | 9 | 32,092 |
| Revised | 850 | 165 | 1,106 |
| Per serving |  |  |  |
| 2001 | 2.2x10-7 | 3.0x10-9 | 1.1x10-5 |
| Revised | 3.0x10-7 | 5.8x10-8 | 3.9x10-7 |

## Summary

**The revised model is completed and undergoing scientific and management review**
**The revised risk assessment report is being prepared for scientific and organizational reviews**
**Deli meats remain among the “highest risk” foods on a per annum and per serving basis**

## Website

_**http://www.foodsafety.gov**_