Microorganisms and Foodborne Illness

Mark Buttner, Ph.D.Professor, Department of Environmental and Occupational Health

School of Public HealthUniversity of Nevada, Las Vegas

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Outline

I. Background – Food QualityII. Microorganisms and FoodIII. Foodborne Illness

A. Food IntoxicationB. Food Infection

IV. Prevention

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• Until mid 1800s – limited/localized problems with food quality

• Most people raised their food at home• Purchased from local farmers/producers• Inspected their purchases

• 1825 - first Agriculture Committee in the U.S. Senate was established

• U.S. Federal Government not involved prior to 1900s

BackgroundButtner

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Background

• After Civil War (1861-1865) – revolutionary change• Growth of cities• Expansion of transportation (refrigerated railcars

and trucks): fresh meat/produce year-round• Rapid development (absent regulation)• Poor hygiene and unethical practices

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Background

• Food Scandals – 19th Century• Adulteration – deliberate addition of inferior or

cheaper material to a pure food product in order to stretch out supplies and increase profits• Harmless ingredients• Toxic substances

• Poisonous food colorings and flavorings

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Background

• Adulteration – deliberate addition of inferior or cheaper material to a pure food product in order to stretch out supplies and increase profits

• Harmless ingredients• Toxic substances

• Poisonous food colorings and flavorings

• Focus shifted from adulteration to contaminants and additives

• Widespread interest in “health foods” and “organic” foods

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Food Contaminants

• Substances accidentally incorporated into foods

• Introduced during harvesting, processing or packaging

• Dirt• Hairs• Animal feces• Fungal growth• Insect fragments• Pesticide residues• Traces of growth hormones or antibiotics

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Food Additives

• Substances intentionally added to food to modify its:

• Color• Appearance• Resistance to deterioration• Taste• Texture• Nutritive value

• Thousands of additives

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Classification of foodborne diseases and etiologic agents

Knechtges, P.L. 2012

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Microorganisms and Food

• Not all relationships between microorganisms and food are bad

• Microbial processes are necessary for a variety of food products

• Cheese, yogurt, buttermilk, cider vinegar• Breads• Sauerkraut, some sausages, pâtés, liver spreads• Alcoholic beverages

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Microorganisms and Food

• Unwanted microbial activity results in• Spoilage of foods

• Economic loss• Loss of nutrient value

• Serious illness

• The ubiquity of microorganisms in soils, air, and water results in natural presence of organisms on foods and food components

• Responsible for vast majority of food “poisoning” incidents in U.S.

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Percentage of reported foodborne disease outbreaks and outbreak-associated illnesses by etiology based on mean annual totals - U.S., 2001–2005

Knechtges, P.L. 2012

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• Acute foodborne infections result in an estimated:• 48 million cases• 128,000 hospitalizations• 3,000 deaths

• 1 in 6 Americans gets a foodborne illness each year• 1 in 1,000 Americans is hospitalized each year• 800 foodborne outbreaks reported annually• More than 250 foodborne diseases

Foodborne IllnessButtner

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Microbial Contamination of Food

• Chemical properties of foods vary• Different foods are colonized by different organisms

that can utilize them as nutrients• Enteric organisms colonize meats, but rarely fruits

(unless subjected to fecal contamination)• Pseudomonas, common in water and soil, is found as a

spoilage organism in fresh foods

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Foods Most Likely to Cause Food Poisoning• Chicken, Beef, Pork, and Turkey• Fruits and Vegetables• Raw Milk, and Products Made From It• Raw Eggs• Seafood and Raw Shellfish• Sprouts• Raw Flour

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Top five microbes that cause foodborne illnesses in the U.S.

• Norovirus• Salmonella • Clostridium perfringens• Campylobacter• Staphylococcus aureus

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Microbes that cause illnesses more likely to lead to hospitalization

• Clostridium botulinum• Listeria monocytogenes• Escherichia coli • Vibrio

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• Rate of growth depends on• Temperature• Nutritional value of food

• Time needed to reach concentration necessary to cause adverse effects

• Size of inoculum• Rate of growth

Microbial Contamination of FoodButtner

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Foodborne Illness

• Food intoxication (food poisoning) • toxin produced by microorganism in food• toxin ingested

• Food infection• microorganism ingested and reproduces in host

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Food Intoxication

• The microorganisms grow in food and produce toxin

• Do not necessarily grow in the host and may not be alive when the food is ingested

• Preformed bioactive toxin• Important Bacterial Intoxications

• Staphylococcus aureus – enterotoxin in food is not destroyed with cooking

• Clostridium botulinum - produces deadly neurotoxin (heat labile)

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Staphylococcus aureus

• Humans are the primary source• 20-40% of all food intoxication cases• Common foods

• Cream pies, pastries• Sauces, gravies• Cooked ham• Chicken/egg salad• Foods held at improper temperature

• Onset of symptoms: 2-8 hrs. (early as 30 min.)

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Staphylococcus aureus• Transmission

• Foods that come in contact with food handler’s hands• Without subsequent cooking• Inadequate heating or refrigeration

• Staphylococcus, if present as a contaminant, proliferates, producing enterotoxins

• Refrigeration slows growth of Staphylococcus• Toxins are relatively heat stable

• several stable at the boiling point• re-heating food not effective

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Staphylococcus Intoxication

• Stimulates T cells that release cytokines, activating inflammation in the intestine leading to gastroenteritis with massive fluid loss from the intestine

• Illness can be severe• Profuse vomiting (may have blood)• Nausea• Abdominal cramps• Diarrhea (may have blood)

• Self-limiting, resolves 48 hours after onset• May require treatment for dehydration• Antibiotic treatment not useful

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Control Measures• Educate food handlers

• Food hygiene• Dangers of working with exposed skin, nose or eye

infections, and uncovered wounds

• Reduce food handling times, store/cook at proper temperatures

• Exclude workers with infections of hands, face or nose

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Clostridium Food Intoxication

• Anaerobic, gram positive endospore-producing bacilli• Common inhabitants in soils• Endospores are heat stable• Spores germinate, cells multiply, and toxin is produced• C. botulinum - botulism

• Approx. 50 cases/yr in US• ~25% fatal

• C. perfringens – food intoxication• Most reported intoxication cases in US• ~250,000 cases/yr

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Clostridium perfringens

• Found in soil, dust, and intestines of animals and humans

• May contaminate food products at harvest and at preparation• Agricultural practices• Food handlers

• Spores inactive if refrigerated immediately after cooking

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• Disease caused by ingestion of large dose• >105 cells• Contaminated and inadequately cooked foods

• Meats, esp. if cooked in bulk• Poultry• Fish

• Insufficient heating and then holding at 20-40°C• Organisms present, but no toxin yet

• 7-15 hours after consumption• Cells begin to sporulate in the intestine• Triggers production of toxin

• Alters permeability of epithelium• Results in diarrhea and cramps• NO vomiting, NO fever

• Symptoms resolve within 24 hours; self-limiting• Rarely fatal

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• Active infections resulting from ingestion of food with microbial contaminants present

• May or may not have a toxin component• Onset of symptoms: 6 hrs. to weeks after ingestion• Similar symptoms:

• Abdominal pain, diarrhea• Dehydration• Vomiting• Prostration• Fever, chills

Food InfectionButtner

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Salmonellosis

• Salmonella spp.• Common foods

• Poultry, meat, sprouts• Eggs

• Onset of symptoms: 6 hrs to 3 days• Some remain carriers for months• Small percentage may develop serious chronic disorders

• Infections occur when:• live bacteria are ingested• survive digestion• reproduce in small intestine (symptoms)

• Prevention: thorough cooking

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Salmonella species and Serotypes

• Genus consists of only two species: S. enterica and S. bangori

• More than 2,500 serotypes (or serovars) recognized

• Taxonomic classification and serotyping are very important to salmonellosis control

• Naming of Salmonella serotypes done by international agreement, but still evolving

• Salmonella enterica ssp. enterica ser. Typhimurium• Salmonella Typhimurium

• http://www.cdc.gov/foodsafety/outbreaks/multistate-outbreaks/outbreaks-list.html

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Transmission of foodborne salmonellosisKnechtges, P.L. 2012

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Campylobacteriosis

• Campylobacter jejuni – 90% of cases• Most common bacterial food poisoning agent• Common foods

• Undercooked chicken, turkey• Unpasteurized milk• Salad or fruit

• Onset of symptoms: 1-10 days• Up to 10% may develop serious, long-term

complications• Prevention: proper cooking, avoid cross-contamination

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Transmission of foodborne campylobacteriosisKnechtges, P.L. 2012

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Classification of 4 Pathogenic E. coli Strains

Strain Reservoirs of InfectionEnterohemorrhagic E. coli (EHEC)(includes E. coli O157:H7)

Cattle are primary reservoir, but other animals and humans may be sources

Enteroinvasive E. coli (EIEC) Humans are the established reservoir

Enteropathogenic E. coli (EPEC)

Humans are the established reservoir

Enterotoxigenic E. coli (ETEC) •Strains are very species-specific for hosts

•Humans are the reservoir for human ETEC disease

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Escherichia coli O157:H7

• Normal flora of healthy cattle• Common foods

• Undercooked beef• Unpasteurized fruit juice• Sprouts, lettuce

• Low infective dose• Grows in small intestine; produces potent toxin, severe damage

to lining of the intestine• Onset of symptoms : 1-10 days• 2-7% of cases result in serious ailment• 60,000 cases with 50 deaths/yr.

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E. coli O157:H7

• Incubation period: 3-8 days• Disease: hemorrhagic colitis • Symptoms: bloody diarrhea, abdominal

cramping, fever• Illness duration: 5-10 days• Children/elderly: Hemolytic Uremic

Syndrome (HUS) - kidney failure, red blood cell death, reduced platelets

• Most serious in children under 5 years of age

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Foodborne transmission of pathogenic E. coli strainsKnechtges, P.L. 2012

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Foodborne Infection - Viral• Viruses do not multiply in food or water

• Suitable/living host necessary for viral replication• Food serves as a vehicle

• Fecal origin• Norovirus• Hepatitis A (HAV)

• Infected persons shed large numbers of viruses in their stool

• Only a few virus particles necessary to cause infection

• Viruses transmitted via food are not easily degraded in the environment

• Most frequent causes• Poor hygiene of food handlers• Contact of food with sewage-polluted water

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Norovirus

• More cases of acute gastroenteritis than any other foodborne pathogen

• Nearly 60% of estimated illnesses, but a much smaller proportion of severe illness, caused by Norovirus

• Genus within the Norwalk-like viruses• Incubation period: 24-48 hours• Lasts 12-60 hours• Sudden onset

• Nausea• Vomiting• Diarrhea

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Norovirus - transmission

• Contaminated food or water• Fecal-oral route• Directly from person to person• Contaminated surfaces/fomites• Transmission difficult to control through

routine sanitary measures• High infectivity and persistence in

environment

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Norovirus - transmission

• Salads• Sandwiches• Produce

• Implicated in 43 of 76 (56%) outbreaks in which a food item was identified

• Food handlers are more likely to be implicated in a norovirus outbreak than a bacterial outbreak

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Norovirus - Illness

• Self-limiting• Increased risk for complications because of dehydration

and electrolyte disturbances• Elderly• Children• Severe underlying medical conditions

• Hospitalization of adults who are otherwise healthy is rare

• Neither a specific antiviral treatment nor a vaccine has been developed for Noroviruses

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Preventing Foodborne Disease

1. Avoid/minimize contamination• Transfer of microorganisms from infected animal or

feces to machinery or hands of worker• Avoid microbial contamination of food through rigorous

adherence to rules of good sanitation and hygiene

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Preventing Foodborne Disease

2. Destroy/denature the contaminant• Proper cooking of food

3. Prevent further spread or multiplication• Maintain environmental conditions that inhibit

the multiplication of bacteria that may be present in small numbers in food

• Danger Zone – temperature range at which the bacteria responsible for majority of outbreaks multiply most rapidly• 41 - 135°F (5 – 57°C)

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References

• Bauman, R.W. 2009. Microbiology: with Diseases by Body Systems, 2nd

edition, Pearson Benjamin Cummings, San Francisco, CA, 2009.• Burlage, R.S. 2012. Principles of Public Health Microbiology. Jones and

Bartlett Learning.• CDC. 2019. https://www.cdc.gov/foodsafety/outbreaks/multistate-

outbreaks/outbreaks-list.html• CDC 2019. https://www.cdc.gov/foodsafety/• Food and Drug Administration. Bad Bug Book: Foodborne Pathogenic

Microorganisms and Natural Toxins Handbook, 2nd ed. http://www.fda.gov/downloads/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/UCM297627.pdf

• Heymann, D.L. (ed.), 2014. Control of Communicable Diseases Manual, 20th edition. APHA Press

• Knechtges, P.L. 2012. Food Safety: Theory and Practice. Jones & Bartlett Learning, Burlington, MA

• Madigan, M.T., J.M. Martinko, and J. Parker. 2002. Brock Biology of Microorganisms, 10th ed. Prentice Hall, Upper Saddle River, NJ.

• Nadakavukaren, A. 2006. Our Global Environment: A Health Perspective, 6th Ed. Waveland Press Inc., Prospect Heights, IL.

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Questions?Buttner

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