The Big 5 Food-borne bacteria

The Big 5
Food-borne bacteria
Carolina Mateus, Ph.D
Dallas, TX. Oct 2013
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Food Safety
• Important to the consumer
• Important to government
• Important to food processors
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Why? Who?
• Microorganisms are responsible for spoilage, large outbreaks of food borne
illness and have huge financial impact.
• Sources:
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Food borne
• Raw or unpasteurized food
• Food mishandling
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13%
Outbreak Causes in the US
1998 - 2007
Bacteria
1%
Virus
Chemicals / Toxins
Environmental (air and water)
Person to person
Parasites
• Low GMP compliance / Inappropriate
HACCP plan / Lack of ownership
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Hand washing / poor hygiene
Separation between RAW and RTE
Sick policy
30%
56%
Microbes are small…
Size
(μm)
# in 1 mm
(1/25 of an inch)
# in 1 inch
0.01
100,000
2,500,000
bacteria
1
1000
25,000
yeast
10
100
2,500
fungi
50
20
500
protozoan
100
10
250
ant*
1000
1
25
virus
1 Bacteria Dividing Every 20 Minutes Equals > 4,700,000,000,000,000,000,000 In 24 Hours.
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Delicate Balance
• Beneficial to humans: digestion, fermentation, industrial process.
• Problematic
• (A) Pathogenic - Causes Diseases.
• (B) Spoilage - Causes Decomposition and off Flavors in Food.
• CDC estimates that each year roughly 1 in 6 Americans (or 48 million people)
gets sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases.
• Indifferent
• Neither Helpful nor Harmful, but adds to the numbers in a product.
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Food Safety - Definitions
• Foodborne Infection - Disease caused by invasion, growth and damage to the host by
microbes.
• Foodborne Intoxication - Disease caused by a preformed microbial toxin present in food.
• Food Poisoning – Result of eating organisms or toxins in contaminated food.
• Parameters •
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Pathogenicity / Virulence of microbe
Critical numbers for intoxication may be lower than for infection.
Killing the bug, does not kill the toxin.
Effect of Host immune system
Mode of entry
• Outbreak - Occurrence of disease from a common origin, involving more than one
individual.
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• Case - Individual involved in an outbreak.
Outbreaks
Many food-borne illness outbreaks go unidentified
due to their:
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small size
long incubation period
geographic dispersion
inability to identify the pathogen
mild cases of illness that do not prompt individuals to
seek medical care
2013
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Listeria in Cheese
Hepatitis A in frozen fruits
Salmonella in Tahini Sesame Paste
Salmonella in ground beef
Salmonella in chicken
E. coli O121 in frozen foods
Salmonella in imported cucumbers
Worst outbreaks in the decade:
• Largest single source outbreak: 2006.
Campylobacter in milk. CA prisons. 1,644 people
affected.
• Largest multi-state outbreak: 2008. Salmonella in
peppers. 1,535 people affected in 42 states.
• Deadliest outbreak: 2008. Salmonella in peanuts. 9
deaths.
• Highest death rate: 2002. Listeria in Deli turkey meat.
8 out of 54 sick people died (15%).
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Outbreaks
•
Outbreaks decline by more than 40% toward the
end of the decade.
•
FDA-regulated foods (produce, seafood, dairy,
eggs, processed foods) were responsible for
more than twice (67%) as many fullyinvestigated outbreaks as USDA-regulated
foods (meat and poultry) (28%).
•
Dairy outbreaks were few but increased in
second half of decade  increased popularity of
unpasteurized milk products.
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Adjusted for consumption, seafood is the most
risky food, followed by poultry.
•
Produce and dairy are the safest.
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Restaurants and private homes are the most
common locations for foodborne illness
outbreaks.
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Contaminated food can cause an estimated 76
million illnesses and 50K deaths annually in the
US, according to the Center for Science in the
Public Interest report for 2009.
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Outbreaks
• E. coli - beef - fecal
contamination of meat
during slaughtering and
processing.
• Salmonella – poultry - Farm
practices, such as crowding
and the use of antibiotics
• In most instances, improper
handling of prepared foods
is the actual cause of
poisoning by Clostridium
perfringens, due to spore
germination.
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Outbreaks
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Seafood is the leading cause of
food-borne outbreaks in the US.
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The majority of seafood outbreaks
were caused by natural toxins, not
destroyed by cooking, rather than by
bacteria or viruses.
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Main cause: improper refrigeration
after harvesting.
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Viruses are the main source of
outbreaks in produce.\
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> 50% of produce outbreaks 
restaurants
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Produce contamination is very
difficult to combat because:
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produce is often served raw.
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pathogens hide in the cracks
of the skin and can be
transferred to the interior flesh
of the fruit during cutting.
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Campylobacter is the most common
hazard associated with dairy.
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Salmonella is the most common
contaminant in eggs.
Not all bugs are created equal
• Shapes
• Rods, Cocci, Spirilum
• O2 Requirements
• Aerobe - Bacillus
• Anaerobe - Clostridium
• Microaerophile - Lactobacillus
• Facultative – E. coli
• Temperature Requirements
• Thermophile (55-80˚C) - Bacillus
• Mesophile (30-45˚C)
• Thermoduric (heat resistant; survive but no growth) - Streptococcus,
Lactobacillus, Bacillus
• Psychrotrophic (cold tolerant) – Pseudomonas, Bacillus, Listeria
• Psychrophile – (10-15˚C)
• Spore formation
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Food-borne infections
Who are we dealing with?
• Safety and spoilage
• Bacteria > viruses >> mold >>> yeast
E. coli
Salmonella
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Listeria
Campylobacter
Staphylococcus
Salmonella
• Cell Facts:
• Gram-negative, non-spore forming motile rod, facultative anaerobe
• Disease (salmonellosis):
• Typhoid Fever, Gastroenteritis - Most common
• Incubation:
• 12 – 36 h for gastroenteritis
• Illness usually lasts 4 to 7 days, and most persons recover without treatment.
• Source: Intestinal tract, fecal material
• Transmission: Person-to-person; by contaminated food or water
• Infectious Dose: 106-109 cells
• Annual Cases in the US: 1M illnesses, 400 deaths
• Challenges:
• Antibiotic resistance, largely as a result of the use of antibiotics to promote the
growth of food animals.
• Can tolerate relatively dry environments; survive up to 24 h on dry surface
• Food commonly affected: poultry and eggs
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Staphylococcus aureus
• Cell Facts:
• Gram-positive coccus
• Facultative anaerobe
• Exotoxins
• No spores
• Disease: From skin infections, to life-threatening diseases. Food poisoning  toxic shock syndrome
(TSS) produced by the exotoxin TSST-1.
• Incubation: 2 – 4 hr
• Source: Skin, nasal passages
• Transmission: Through food handler hands
• Infectious Dose: >106 cells
• Annual cases in the US: 250K illnesses
• Challenges:
• Heat stable toxin; survives pasteurization
• Extensive survival outside host:
• Carcass and organs - up to 42 days; floor - 7 days; glass - 46 hours; sunlight - 17 hours; skin from 30 min
to 38 days
• Food commonly affected:
• Any mishandled food
• Dairy (cows with infected udders)
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Escherichia coli
• Cell Facts:
• Non sporulating, motile, aerobic Gram negative rod, toxin producer (STEC)
• Disease:
• Pathogenic groups
• Enterotoxigenic, Enteroinvasive, Enteropathogenic
• Enterohemorrhagic (EHEC); best known strain is E. coli O157:H7
• Incubation: 3- 4 Days
• Source: Intestinal tract of warm blooded animals; especially pigs and cattle
• Transmission: Fecal contamination
• Infectious Dose: 10 -500 cells (low!)
• Annual Cases in the US: 70 K
• Challenges:
• May grow at 8°C or higher
• Heat tolerance is not unusual - readily inactivated
• Survives in cream for 10 d, in hamburger meat and contaminated soil for over 2 mo
• Food commonly affected:
• Hamburger meat, raw milk, apple cider, drinking water, swimming pool water, surface water,
fruits and vegetables.
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Campylobacter
• Cell Facts:
• Gram negative spiral-shaped bacteria, microaerophilic, very susceptible to drying and
temperature extremes
• Disease:
• Intestinal track disease, but can get to bloodstream and be fatal.
• Incubation: 1-10 days
• Source: Environment, cattle
• Infectious Dose: <500 cells
• Annual Cases in the US: 850K illnesses, 76 deaths
• Challenges:
• Will survive in moist environments (including droplets), especially at lower temperatures, but
cannot tolerate drying; Feces - up to 9 days; milk - 3 days; glass slides - 24 hours; water - 2 to 5
days
• Food commonly affected: unpasteurized milk, raw meat, contaminated water
• Reservoirs: environment, intestinal tract
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Listeria monocytogenes
• Cell Facts:
• Gram-positive, non-spore forming, aerobic bacilli, Psychrotrophic
• Disease:
• Flu-like
• Can pass to fetus causing spontaneous abortions
• Incubation: 3 – 70 days
• Source: Feces contamination from cattle or domestic animals
• Infectious Dose: Not known (<1000 cells)
• Annual Cases in the US: 2,500 ilnesses; 255 deaths
• Challenges:
• Able to grow at low temperatures ( refrigerator). Survives well in soil, water, food, feces
• Food commonly affected:
• Uncooked meats and vegetables. Unpasteurized milk or foods made from unpasteurized milk
• Processed foods that become contaminated after processing (soft cheeses, cold cuts).
• Common plant locations:
Internal
• Drains, conveyors, floors with pooled liquid, packaging equipment, blenders, racks for storing or
transporting finished product, spiral freezers, cracks in walls that retain moisture, condensate,
insulation in walls / pipes, moist cleaning tools.
Microbial control basics
• Limit initial numbers
• clean plant and clean ingredients = clean product.
• Moisture
• Salt and sugar are used to bind water molecules, thus making them unavailable to
microorganisms.
• Drying foods (beef jerky, dried fruits) removes the water.
• pH
• Limited growth below pH 5
• Temperature
• Cooking, pasteurizing, etc
• Freezing, cooling.
• Perform appropriate testing
• Appropriate use of cleaning and sanitizing chemicals
• Appropriate equipment design
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Steps to control microbial contamination
• Design and implementation of HACCP plan
• Adherence and regular cGMP training
• Hand washing!!!!
• RAW vs. RTE separation:
• Assure that no raw product comes in contact with floor around processing
and packaging equipment
• Rinsing into drains without proper separation will not help
• Absolutely no cross-connections between RAW and RTE
• Promptly repair cracks or openings
• No pooling of water in floors, hoses, etc
• Isolate wet process areas from other production areas, especially from
packaging
• Special attention to condensate
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Steps to control microbial contamination
• No tools / parts on floor during cleaning
• Aerosolization
• Never use a high pressure hose to clean a drain
• After initial rinse, wash floors. Washing floors after cleaning equipment may
cause secondary contamination
• No tight gaps in equipment or spot soldering
• Include environmental monitoring / swabbing
• Sampling training and control  only appropriate samples yield
workable results
• Supply chain control
• Optimized cleaning / sanitization regime
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Hand Washing
• Estimated that 400 deaths per year could be prevented by
proper hand washing (CDC)
• According to the CDC unwashed hands are the second
leading cause of food-borne illness and that hand washing
is the single most effective means of preventing food
contamination.
• Hands-free operating sinks and soap dispensers offer
even greater reduction of contamination.
• A hand sanitizer with alcohol is also recommended prior to
workers commencing plant functions.
• Anti-bacterial soap has been shown to be no better than
regular soap at destroying pathogens. The secret is
scrubbing under running water for at least 20 seconds.
• The following procedure should become an accepted
practice in hand washing; rinse, soap, scrub, rinse and
sanitize.
• The FDA requires a water temperature of 100˚F for hand
washing and this is the Food Code.
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Microbial testing recommendations
• Have a sound consistent plan.
• OK to have initial random sampling
• As “hot spots” are found, follow them over time
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Train personnel
Limit number of people taking samples
Control sample chain
Take microbial swabs/sponges of environment
Select growth media, sampling equipment and sampling technique wisely
Audit outside testing lab and transport company
Track data and perform trend analysis
Keep records
• Define base line
• Identify and question abnormal/out of character results
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Let’s all do our part in KEEPING FOOD SAFE
“The role of the infinitely small
is infinitely large. ”
-Louis Pasteur (1869)
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