MawillRodriguez

Incidence of Listeria in Rural Home Environments with and without Ruminant Animals: 

Incidence of Listeria in Rural Home Environments with and without Ruminant Animals Mawill Rodríguez-Marval Swift Seminar Spring 2007

Introduction: 

Introduction Listeria and ruminants Listeria monocytogenes has been identified as a major infectious agent causing neurological syndromes and uterine infections in bovine, sheep and goats (Rebhun, 1982. Low and Donachie, 1997) Animals and birds may be carriers of Listeria, and they can shed the pathogen and contaminate the farm environment without showing clinical signs of infection (Oliver et al., 2005) In a cheese producing farm, L. monocytogenes was possibly transfered from contaminated feeds to the milk supply facility, and humans (Wagner et al., 2005)

Introduction: 

Introduction Food Safety, consumers and the household environment Most research about Listeria incidence has been done at the production and retail level Live animals are the first step in the food chain Consumers are the last step in the food chain

Introduction:Why the consumer and animals?: 

Introduction: Why the consumer and animals? Least studied step in the food chain Consumption patterns and hygiene practices in private homes should be included in exposure assessments (Christensen et al., 2005) Perception that producers and restaurants have the most responsibility for food safety (Cates et al., 2006) It has been estimated that from 30% to as 80% of foodborne diseases are caused by events happening in the home (Christensen et al., 2005)

Introduction: 

Household environment Farm environment Ruminants Introduction

Objectives: 

Objectives To compare the incidence of Listeria in household environments with and without direct physical contact of residents with ruminant animals or their environment To determine the frequency of human fecal carriage of L. monocytogenes among residents of households with or without ruminants To determine pathways of L. monocytogenes contamination from ruminants into the household environment and food To determine safe/unsafe behaviours related to Listeria incidence

Experimental Design: 

Experimental Design Three year project Year one: Recruiting of participants Application of surveys, questionnaires and observations Sampling Year two: Education of participants regarding food safety and home hygiene Year three: Sampling Evaluation

Materials and Methods: 

Materials and Methods Recruitment and visits 54 Colorado households were recruited (27 each with and without ruminants) Households were visited every 3-4 weeks, 4 visits total Data collection Behavioral data Survey Food handling and eating preferences Kitchen audit Interview with the primary responsible person for shopping and preparation of meals

Experimental design: 

Experimental design 27 households 27 households 4 visits (3-4 weeks apart) 4 visits (3-4 weeks apart) 3 food samples 5 environmental samples Refrigerator Kitchen sink Washing machine Shoes Kitchen countertop/Work gloves/Utility sink 1 Ruminant fecal sample 1 Human stool sample 3 food samples 5 environmental samples Refrigerator Kitchen sink Washing machine Shoes Kitchen countertop/Utility sink 1 Human stool sample FARM NON-FARM

Behavioral data analysis: 

Behavioral data analysis Scores Household cleanliness Personal hygiene Refrigerator cleanliness Awareness of pathogens Avoidance of unsafe food Perishable food handling Pet handling Outdoor animals handling Relationships between scores and incidence Comparison of scores by household type Comparison of behavior by household type and by Listeria incidence

Materials and Methods: 

Materials and Methods Sample collection Food samples were collected with a clean spoon by the participant and transferred to a Whirlpak bag Human stool samples were collected in a Commode Specimen Collection System Ruminant fecal samples were collected from the ground with a sterile wooden tongue depressor and transfer to a Whirlpak bag Environmental samples were collected using a sponge moistened in 10 ml peptone water, by the participants. All samples were placed in a cooler with ice-packs, transported to the lab, and analyzed within 24 hours of collection

Materials and Methods: 

Materials and Methods Microbiological data analysis All samples were tested for Listeria presence Food and fecal samples 25 g Environmental samples Sponges 1:10 dilution in Universal Pre-enrichment Broth 1:10 dilution in Fraser Broth PALCAM and TSAYE streaking Presence/absence Biochemical confirmation of Listeria Colonies were picked

Results: 

Results Results by sample type Positives/total samples H1: refrigerator; H2: kitchen sink; H3: washing machine; H4: shoes; H5: countertop, utility sink or work gloves

Results: 

Results Results by sample type (%) H1: refrigerator; H2: kitchen sink; H3: washing machine; H4: shoes; H5: countertop, utility sink or work gloves

Results: 

Results Listeria was recovered at least once from each type of sample Listeria was not recovered from human fecal samples Carriage in stools is probably transitory (Grif et al., 2003) Carriage rate can vary from 0.8% to 26% (Grif et al., 2001) Results suggest cross-contamination within the household environment

Results: Possible scenarios of cross-contamination: 

Results: Possible scenarios of cross-contamination Kitchen sink Household 1103 Visit #1 (Cow) Cottage cheese Creamed chipped beef Refrigerator Household 1227 Visit #2 Queso fresco Lettuce Visit #1: Sliced deli cheese Household 1202 Visit #1 Visit # 2: Kitchen countertop Household 1227 Visit #3 Refrigerator

Results: Possible scenarios of cross-contamination: 

Results: Possible scenarios of cross-contamination Kitchen sink Household 1109 Visit #1 (goats) Washing machine Cheddar cheese Household 1109 Visit #3 (goats) Household 1109 Visit #2 (goats) Refrigerator Kitchen sink

Results: Possible scenarios of cross-contamination: 

Results: Possible scenarios of cross-contamination Documented cases of cross-contamination In a household of elderly individuals, three food items, the kitchen sink and fecal samples were positive for a genetically indistinguishable L. monocytogenes pulsetype (Wagner et al., 2007)

Implications: 

Implications Listeria may enter the household environment via exposure to outdoor animals Cross-contamination between food and surfaces can occur inside the household environment It is necessary to educate consumers about food handling and hygiene practices that minimize the risk of being exposed to Listeria in the home

Acknowledges: 

Acknowledges This work was supported by the National Integrated Food Safety Initiative of the United States Department of Agriculture Cooperative State Research, Education and Extension Service and by the Colorado State University Agricultural Experiment Station.