Lecture 9 Flashcards
Bacillus Cereus
- Gram ____, facultative _____, ______- forming rod
- gram +, faculative anaerobe, endospore-forming rod
Bacillus cereus two forms:
- emetic (vomiting)/ 7 serotypes
- diarrheal/ 7 serotypes
Bacillus cereus is ______ in the environment where it _____, _____, and _______
ubiquitous, germinates, grows, sporulates
Bacillus cereus illness occurs due to ______ and _______ of spores in contaminated food and subsequent production of toxins
survival and multiplication
Bacillus cereus tolerates ____% salt concentrations
7.5%
Bacillus cereus has an estimated ______ cases/yr in Canada
37,000
Is bacillus cereus a notifiable and a reportable disease?
Not a notifiable nor a reportable disease
B. cereus is primarily linked to foods that have been ____________
cooked and cooled too slowly
B. cereus is a FBI caused by ______________
ingesting large numbers of bacterial cells and/or spores in contaminated food (diarrheal) or food contaminated with pre-formed toxin (emetic)
B. cereus: ______ and ______ destroyed by heat
- vegetative cells (56C for 5 minutes)
- spores (126C for 90 minutes)
B. cereus: sanitizers ______ vegetative cells, spores are _______
destroy, highly resistant
B. cereus caused by _________ to cooked foods
cross contamination
B.cereus diarrheal syndrome toxin?
enterotoxin produced in intestine
B. cereus emetic syndrome: emetic toxins
- pre-formed in food
- stable from pH of 2-11
- heat stable at 126C for 90 minutes
- temperature abuse= cells grow and produce emetic toxin
- reheating will not help
B. cereus diarrheal syndrome symptoms:
- mimics ___?
- cramps
- watery diarrhea
- nausea
- very little vomiting
- fever uncommon
- mimics C. perfringens
- Incubation period: 6-15 hours
B. cereus emetic syndrome symptoms:
- nausea
- vomiting
- diarrhea (<30%)
- fever uncommon
- Incubation period: 0.5 hours, can be 15-30 minutes
B. cereus foods related to diarrheal syndrome?
- meat and vegetable soups often implicated
- other food vehicles: milk, fish, mashed potatoes, pudding, cereal dishes with corn
B. cereus foods related to emetic syndrome?
- cooked rice (frequent); been called fried rice syndrome
- other food vehicles: pasteurized cream, spaghetti, mashed potatoes, vegetable sprouts, reconstituted infant formula
What is the correct way to prepare rice? (3 steps)
- rice should be boiled in small quantities during the day
- after boiling, rice should be kept hot or cooled rapidly
- under no circumstances should cooked rice be stored at room temperature for longer than 2 hours
Bacillus cereus:
- infectious dose
- type of illness
- route of transmission
- incubation period
- duration of illness
- mortality
- diagnosis
- treatment
- 10^6 organisms/g (range 10^5 to 10^8)
- toxin/enterotoxin
- ingestion of contaminated food (often starchy foods)
- diarrheal type: 6-15 hours; emetic type: 0.5-6 hours
- lasts 24 hours (typically self limiting
- low mortality rate
- diagnoses with faeces or vomitus
- self limiting illness; supportive treatment for dehydration
B. cereus growth factor:
- pH
- temperature growth range
- oxygen
- water activity
- biofilm formation
- foods associated with illness
- other sources
- 4.9 to 9.3
- 4C to 48C *small % of strains are psychotropic; typically 10C to 48C (optimum is 28C to 35C)
- facultative anaerobe
- 0.91-0.95
- yes; biofilms also produce spores
- rice, pasta, often starchy foods
- widespread in the environment and often isolated from soil and vegetation
Staphylococcus aureus:
- gram ____, ____-forming
- ____ species and subspecies in the genus Staphylococcus
- Staphylococci are _____ and _____ to eradicate
- causes ______, _____, _____, _____, and ______
- highly tolerant to _____ and ______ (can grow in these foods)
- Gram positive, non-spore forming
- 32
- ubiquitous; impossible
- staphylococcus food poisoning, toxic shock syndrome, pneumonia, post-operative wound infection, and nosocomial bacteria
- salt and sugar
MRSA stands for:
Methicillin-resistant staph. aureus (can be foodborne)
Is S. aureus a common food poisoning?
Yes
S. aureus illness from ingestion of ________
enterotoxin pre-formed in food (9 types- A-J); heat stable
S. aureus symptoms are generally _____ and recovery is ______= illness ______ reported
mild symptoms and rapid recovery; rarely reported
Primary reservoir for S. aureus is ______
humans
Incubation period for S. aureus is _________
- short (but not as short as B.cereus)
- 1-6 hours, typically 2-3 hours
S. aureus has an estimated of ______ cases per year in Canada
25,000 cases
Is S. aureus a notifiable and reportable disease?
It is not a notifiable disease nor a reportable disease
S. aureus symptoms:
- vomiting
- abdominal cramping
- diarrhea
- nausea
- severe cases: dehydration, headache, muscle cramping, changes in blood pressure and pulse
Foods related to S. aureus?
- foods with improper food handling and temperature abuse
- outbreaks associated with:
- pork
- bakery products
- beef
- turkey
- chicken
- eggs
- soft cheeses
- RTE foods
Staphylococci can exist in any and all foods that are ______ or ______
handled directly by humans or are of animal origin
What is the percentage of population that is a carrier for S. aureus?
approx 25% (hair, skin, repository tract)
Contamination of S. aureus by __________ or __________
direct contact by workers with hard or arm lesions or by coughing and sneezing
S. aureus enterotoxin
- heat destroys _____ but not _____
- toxin may be _____ in the food
- cells but not enterotoxins
- pre-formed
-Staphylococcal enterotoxins are resistant to ________ which allows them to ________
proteolytic enzymes; transit intact through the digestive tract
What is the most common Staph enterotoxin?
Staphylococcal Enterotoxin A
Foods at risk with S. aureus
- significant food handling
- allowing foods to remain at room temperature
S. aureus infectious dose?
- intoxication dose of SE is less than 1.0 microgram
- 10^5- 1-^6 organisms/g in food
S. aureus type of illness?
- intoxication
- enterotoxigenic S. aureus or ingestion of the performed enterotoxin
S. aureus route of transmission?
- ingestion- contaminated food/objects
- direct contact with wounds
S. aureus reservoir?
- humans (occasionally cows, dogs, fowl)
S. aureus duration of illness?
several hours to one day
S. aureus mortality?
uncommon
S. aureus diagnosis
feces and vomitus
S. aureus treatment
self limiting illness
S. aureus pH level?
- 4.5 and 9.3; optimum between 7.0 and 7.5
- enterotoxin produced between 4.8 and 9
S. aureus temperature growth range?
- 7C to 48C; optimum 35C
- enterotoxins produced in 10-45C
S. aureus oxygen?
- facultative anaerobe
S. aureus water activity
- growth at >0.83; optimum at 0.99
- enterotoxin produced at >0.87
- can survive for extended periods in a dry state
S. aureus biofilm formation
Yes
S. aureus foods associated with illness?
- milk (raw and pasteurized), soft cheeses, cooked meats, vegetables, RTE meats
- foods that have significant food handling and temperature abuse
S. aureus other sources?
air, dust, sewage, water, milk, and food, or on food equipment, environmental surfaces, humans and animals
Ways too prevent S. aureus (3 tips)
- focus is to prevent enterotoxin production
- good food handler practices
- food time and temperature control (below 4C or above 60C)
Listeria monocytogenes are gram ___ rod, _____ forming
- Gram positive, non-spore forming
L. monocytogenes are _____- tolerant
salt-tolerant
L. monocytogenes are ______ and survives well in ____ and _____ foods. They may survive ______. Inactivated above ___C.
- psychotropic; refrigerated and frozen
- drying
- 70C
L. monocytogenes are ________ (soil, dust, vegetation, water, sewage)
ubiquitous
L. monocytogenes are _______ and non-_________
- serotypes __, ___, ___, and ___ cause __% of infections
pathogenic and non-pathogenic
- 1/2a, 1/2b, 1/2c, and 4 cause 95% of infections
L. monocytogenes: are symptomatic or asymptotic carriers common?
asymptomatic
With L. monocytogenes illness, ______ treatment is necessary
antibiotic
Is L. monocytogenes a notifiable or reportable disease?
It is a notifiable disease and a reportable disease
(listeriosis was removed from notifiable disease list after 1999 but was returned in 2007)
L. monocytogenes symptoms?
- most people are asympomatic
- gastroenteritis (flu like: fever and headache)
- sometimes nausea, vomiting, diarrhea
- invasive (meningitis and septicaemia)
Groups predisposed to L. monocytogenes?
Why is it invasive in these groups?
- elderly
- immunocompromised/underlying conditons
- pregnant women (20x more susceptible)
- facultative intracellular organism (resistant and able to hide and survive in immune cells)L. monocytogenes
Most important risk factors for L. monocytogenes?
- consumption of soft cheeses and RTE foods
- BUT has the potential to be present in all raw foods. Cooked foods can also be contaminated, usually as a result of post-process contamination
L. monocytogenes infectious dose
- as low as 1,000 cells
- vary with the strain and susceptibility of the host
L. monocytogenes type of illness
Infection
L. monocytogenes route of transmission?
- consumption of contaminated foods
- mother to newborn
L. monocytogenes reservoir?
soil, forage, water, mud, livestock food, animals, humans
L. monocytogenes incubation period?
variable, 1 day to 3 months; median of 3 weeks (makes it difficult to investigate outbreaks of listeria)
L. monocytogenes duration of illness
depends on type of illness and severity
L. monocytogenes mortality?
High case fatality rate
- 15-30% with normal infection
- 70% with meningitis
- 50% with septicemia
- 80% with perinatal/neonatal infections
- 50% with newborns
L. monocytogenes diagnosis
blood, cerebrospinal fluid, and cultures from other sterile sites
L. monocytogenes treatment
depends on the type of illness and severity
L. monocytogenes pH growth factor
4.4 minimum, 9.6 maximum
L. monocytogenes temperature growth range
-0.4-50C (can multiply in contaminated refrigerated foods)
L. monocytogenes oxygen
facultative anaerobic
L. monocytogenes water activity
- 0>0.92 (low)
- able to grow in environments of up to 10% salt and survive in 20-30%
- may survive food drying processes
L. monocytogenes biofilm formation
yes; resistance to sanitizers and disinfectants and transfers to food products
Foods associated with L. monocytogenes
milk (raw and pastuerized), soft cheeses, vegetables, RTE meats (deli, hot dogs, etc)
L. monocytogenes other sources
can be in all raw foods
Preventing Listeriosis- Consumer (6 tips)
- cook foods to regulation temperatures
- avoid cross-contamination; clean raw vegetables and fruits, kitchen surfaces, utensils, separate surfaces/utensils, storage of raw and RTE foods
- wash your hands
- only eat pasteurized dairy products
- keep leftovers for a maximum of four days, but preferably for only 2-3 days
- reheat leftovers to an internal temp of 74C
Preventing Listeriosis- Industry (4 tips)
- Rigid environmental sanitation programs
- HAACP program to ensure microbiological safety of products
- trained, knowledgeable, supervision for the sanitation operation
- policy for sampling of RTE foods
