ENVR 191

Food Safety and Foodborne Disease

Lecture 1

December 3, 1999

Mark D. Sobsey

Sources of Foodborne Enteric Microbial Contamination• Food handler‑associated contamination

– Inadequate personal hygiene fecal contamination of foods (e.g., hands)

• Food processing– Equipment, packaging and personnel contaminate foods during processing

• Food Storage: time and temperature abuse bacterial growth• Fecal contamination prior to harvest or collection

– Animal foods contaminated naturally by infection (e.g., salmonella)– Surface contamination (e.g., feces on fur, feathers, hooves, etc.)– Shellfish and other fish contaminated in their environment

• Fecal (sewage) contamination of water pathogen uptake by filter‑feeding on waterborne particles

– Fish and shellfish naturally colonized by aquatic pathogens• Vibrio cholerae in copepods, fish and shellfish

– Produce contaminated by irrigation with sewage or contaminated water or fertilization with nightsoil (feces) or animal feces.

– Soil contaminating plants and animals with bacteria, fungi, etc.

Foods Implicated in Foodborne Illness: Meats• Red Meats

– High contamination in comminuted and processed meats (e.g., ground beef, sausage)

– High surface area, increased contact with processing equipment; increased handling; variety of sources from the animal (organs, trimmings, etc.).

» Ex., E. coli O157:H7 outbreaks due to undercooked hamburger

• Poultry– High contamination levels in cut‑up poultry

• Increased handling, processing and contact with common equipment • Salmonella and campylobacters are prevalent in some poultry flocks

– can contaminate an entire processing plant via equipment and process baths (e.g., chiller tank)

– Eggs• Endogenous contamination by Salmonella enteritidis in some flocks

– Time and temperature abuse leads to proliferation in the egg» Raw/undercooked eggs a source of exposure and infection

Foods Implicated in Foodborne Illness: Fish• Contamination depends on type of seafood,quality of harvest

water and amount of processing, handling and storage.• Bivalve mollusks (oysters, clams, mussels, etc.); filter feeders

– Accumulate enteric pathogens from fecally contaminated waters– Acquire high levels of vibrios from their environmental waters

• Crustaceans (e.g., crabs)– Acquire some pathogens by feeding on mollusks– Acquire high levels of vibrios from their water environment

• Vibrio levels can increase during handling, processing and storage, especially if temperatures are too high.

• Fin fish– Outer surface and epithelial lining (e.g., gut) contamination by

enteric microbes in fecally contaminated waters; – Contamination during processing (e.g., filleting).– Endogenous contamination:

• Ex:: Diphyllobothrium latum; fish tapeworm; anemia; undercooking

Other Foods Implicated in Foodborne Illness• Produce (fruits and vegetables)

– fecal contamination in irrigation water and other fecal sources (animal droppings, birds, etc.)

– inadequate or unsanitary picking, washing or processing.• Dairy Products

– In developed countries milk and related dairy products are usually made from pasteurized milk.

• Raw milk and products (e.g., cheeses) made from unpasteurized milk are high risk of bacteria contamination

– salmonella, campylobacter, brucella, yersinia, listeria,).• Unpasteurized fruit juices and other beverages

– fecal contamination from animal and human sources• Deli, "Fast" and Restaurant Foods

– salads, sandwiches, other fast, deli or restaurant foods– become fecally contaminated during preparation and handling

• Cereal and Grain: inadequate storage of cooked rice/grain

Methods to Control Fecal Contamination of Foods - I• Prevent exposure to fecal contamination in the environment, after

harvest or during processing, preparation and handling• Maintain sanitation in the environment:

– harvest shellfish only from waters that are not fecally contaminated;– irrigate fruits and vegetables with non‑fecally contaminated water.– fertilize fruits and vegetables with uncontaminated fertilizers.

• Maintain uninfected herds and flocks of animals– Immunize animals against infectious diseases:

• Brucella abortus: brucellosis from cattle; raw milk/dairy products– Colonize animals with harmless microflora:

• Colonize baby chicks with harmless bacteria competitive to Salmonella– Destroy animals harboring pathogens:

• Bovine Spongiform Encephalopathy (BSE; “mad cow” disease);– Caused by a prion able to infect humans (neural tissue in meat)

Methods to Control Fecal Contamination of Foods - II

• Maintain adequate hygiene and sanitation during harvest, processing, storage and distribution.

• Source control: use of non‑fecally contaminated foods and ingredients;

• Use clean water for washing, processing, cleaning and worker hygiene;

• Adequate human and food waste treatment and disposal facilities• Plant and equipment sanitation: clean, sanitize, etc.• Personal hygiene, food handling practices and employee health

(education, training and policies).• Criteria and standards and guidelines for fecal contamination

(pathogens and microbial indicators).• Inspection, monitoring and surveillance (product testing)