Food Microbiology Unit 5 Flashcards
(30 cards)
Bacillus cereus etiology
- gram + rod
- spore forming
- facultative aerobic
- motile most
Bacillus cereus types of infection
emetic and diarrheal
- emetic means onset of symptoms much faster
- –caused by ETE toxin
- –30 min- 6hours
- –nausea, vomiting, abdominal cramps
- – usually STARCHY
- Diarrheal
- –6-15 hours
- –can be broken down by heat
- – watery diarrhea, abdominal cramps
- –usually with protein
Bacillus cereus development of disease
- infection = becteri
- intoxication = toxin
- toxin is heat stable
Bacillus cereus foods and reservoir
foods in temperature danger zone are a big proponent
-FRIED RICE = emetic
inadequate refrigeration and reheating
Reservoir: soil and vegetation
-Infectious does: 100,000 to 100,000,000 cells (infection)
Bacillus cereus growth characteristics
temp: mesophilic
— optimum: 28-35 degree C
— Range: 4-48 degree C
pH: tolerate 4.9-9.3
—- more rugged because of endospores
aw: 0.95, halophilic
–tolerates 7.5% salt concentration
Bacillus cereus epidemiology
year round,
food: beef, turkey, RICE, beans, veggies
fringens= “break into pieces” - gas gangrene
Clostridium pefringens etiology
Gram + rod, endospore forming, non-motile, AEROTOLERANT anaerobe (doesn’t use o2)
- -Type A = CPEnterotoxin, diarrhea
- Type C = b toxin necrotizing colitis
Clostridium pefringens growth requirements
temp range: 15-55 degree C --- optimum: 43-47C pH: range: 5-9 --- optimum: 5-6 aw: 0.96 --salt concentration: 5%
Clostridium pefringens characteristics of disease
-causes toxicoinfection
Two forms:
-Gastroenteritis: watery diarrhea and mald abdominal cramps
-Enteritis necrotitis: abdominal pain and distension, diarrhea, vomiting, and patchy necrosis of small intestine
—- can be fatal
Incubation period: 16 hours
Duration: 12-24 hours
Clostridium pefringens pathogenesis
-Doubling time is 10 minutes under optimum growing conditions
-enterotoxin is released when vegetative cell is lysed- after sporulation
-pig-bel disease involves the production of beta toxin
Infectious does: 1,000,000 cells or spores
Clostridium pefringens food and reservoir
- requires high protein food because it can only synthesize 13 of the 20 amino acids
- commonly found in raw meat and poultry
Clostridium pefringens epidemiology
commons foods: beef, poultry, and pre-cooked foods
-occurs where food is prepared in large quantities and left warm
Clostridium botulinum four forms
infant, wound, food-borne, weaponized
Clostridium botulinum LD50
lethal dose is 50% of people
= 0.4 nanograms/kilogram of body weight
Clostridium botulinum development of disease
INTOXICATION
Incubation period: 12-36 hours
Signs and symptoms: nausea vomiting, visual impairment, loss of normal mouth and throat function
–descending flaccid paralysis
Cause of death: respiratory failure
Initial treatment: antibody/antitoxin
-inhibits release of acetylcolene in the muscle tissue which means the neurotransmitters never get the message
Clostridium botulinum prevention and control
- endospores very resistant to radiation
- EDUCATION to improve canning methods
- heating canned foods for 10 mins before eating- boiling
- never give children honey
Clostridium botulinum food, reservoir and transmission
soil, water, and sewage
Transmission= ingestion of toxin in contaminated food,
-contamination of a wound
-ingestion of endospores by infant
-found in fish, meats, HONEY, and veggies
Listeria monocytogene etiology
gram + rod, flagella all over, psychotropic: grows from 0-45 degrees C
Listeria monocytogene growth requirements
pH: grows at 4.4 or greater. Can still survive t lower pH
aw: grows at 0.93 and above. Survives at 0.83
Salt: grows in moderate salt concentrations. 6.5%, halophile
Listeria monocytogene foods
ready to eat foods = problem
Listeria monocytogene pathogenesis
–Can swim into neighboring cells
– lives in phagocytes, no immunity function can kill it
-TWO TYPES:
-Diarrheal- intestines, most people do not experience any illness, incubates in a few hours to 3 days. Fever, muscle aches, nausea, vomiting
-invasive- brain and placenta, incubates anywhere from 3 days to 3 months. Initial symptoms and same as diarrheal but later is spreads to nervous system leading to headache, stiff neck, confusion, convulsions, and meningitis
-Case fatality rate is 15-30%
-
Listeria monocytogene spread of infection/ food/
ready to eat foods = problem
- raw or unpasteurized milk
- cheeses-especially soft cheese
- ice cream
- raw veggies
- raw meat and poultry
- fermented raw meat sausages and hot dogs and deli meat
Listeria monocytogene prevention and control
Reservoir: moist environments, soil and decaying plant and fecal matter
-Sources of contamination: food workers, incoming air, raw materials and food-processing surfaces
Listeria monocytogene dose
- Infectious dose: depends on health of human, varies form 0.3 CFU to 10^9 CFU
- Why is this a new microbe?
- more refrigeration, less competition
