Food Microbiology Flashcards
Microbial Growth and Food Spoilage
-Perishable food: fresh food
-Semi perishable food: potatoes and nuts
-Stable or Nonperishable food: flour and sugar
What is a major factor in food falling in certain categories?
-Water content
-more water, more perishable
Does microbial growth always mean spoilage?
-NO
-fermentation often preservers food
Methods of Food Preservation
-Growth inhibition method
-Killing of microbes
Growth inhibition methods
-Storage temperature
-Acidity
-Decreased water activity
-Chemical preservatives
Storage Temperature
-refrigerate = 4°C, psychrophilic organisms can still grow
-Freeze = -20°C, long term
Acidity
-pickling
-In some cases is a result of fermentation
-Acetic acid = vinegar
Decreased water activity
-drying
-add sugar, add salt
Chemical preservatives
-Some are not to bad
-Other are very bad for your health
Killing of Microbes
-Canning
-Irradiation
-Pasteurization
Canning
-Sterilization
-heating time requires to kill bacterial spores
-green beans, beans, peas
-some things cannot be canned because they disintegrate when heated to sterilizing temperature
What should a can look like?
-Good=indent
-Not good=no indent, gas has formed
-Swelling=lots of gas!
-dropped=gas created pressure and can exploded
Irradiation
-decreases viable counts
-may not sterilize
-Co, gamma
Pasteurization
-decreases viable count
-does not sterilize
Useful microbes in food
-fermented food
-sugars are converted to alcohol or acid
-fermentation products are inhibitory to other organisms
-In some cases, other antimicrobial compounds are produced like simple antibiotics
Dairy foods: cheese, yogurt, and buttermilk
-Lactic acid
-Lactococcus
-Lactobacillus
-Streptococcus thermophilus
-Propionibacterium = Swiss chesses
Alchol
-Zymomonas
-Saccharomyces
Baking
Saccharomyces cerevisiae
Meat products
-Pediococcus
-Lactobacillus
Vegetables
-Leuconostoc
-latic acid bacteria
Vinegar
-Acetobacter=acetic acid
Soy Sauce
-Aspergillus = fermentation of fungi
Common causes of foodborne illness in US
-Passed from animal carries or environmental
-Passed from infected food service workers
Illness passed from animal carries or environmental sources and cases per year
-Campylobacter species = 2,000,000
-Salmonella species = 1,340,000
-Clostridium perfringens = 248,000
-Staphylococcus aureus = 185,000
-E. coli O157:H7 = 63,000 (hemorrhagic)
Illness passed from infected food service workers and cases per year
-Noroviruses = 9,200,000
-Real #1 virus
What does O mean in this E. coli O157:H7?
-O is the antigen
Food Infection
-ingestion of food that contains a pathogen
-the pathogen grows inside the human, causing disease
-MAY or MAY NOT be “self-limiting”
Food Poisoning = Food intoxication
-Ingestion of food that contains a toxin
-Generally the microbe that produced the toxin does not grow inside the human
-symptoms are result of the performed toxin
-Often self -limiting
What does Self-limiting mean?
-means that symptoms pass in short time (days)
Enterotoxin
-food intoxication
-diarrhea symptoms
Staphylococcus aureus
-heat stable enterotoxins
-Nausea, vomiting, diarrhea (1-6 hours)
-Egg/meat salads, salad dressing, desserts, meat, improper heating/cooling
Clostridium perfringens
-Spore former (can survive cooking)
->10^8 cells ingested
-sporulation occurs in small intestine
-produces CPE
-Diarrhea and cramps (7-15 hours)
-Chili, salads containing meat, improper heating/cooling
What is CPE
-C. perfringens enterotoxin
Step sin C. perfringens acute food poisoning
-Contaminated food is cooked and spores survived cooking
-germination occurred when food cooled down
-Cell grew rapidly in warm, anaerobic food
-Person eats contaminated food
-Bacteria pass from stomach to SI
-pH shock induces sporulation
-Sporulation and enterotoxin (CPE) synthesis in SI
-bacteria breaks open releasing spore and toxin
-CPE binds to epithelial cell, causes diarrhea and dispersion of spore
Does heating drive off O2?
-Yes
What type of cell does contaminated C. perfringens food contain?
vegetative bacterial calls
What do spores want to do?
-Spread
What is Clostridium botulinum: Adult botulism?
-food poisoning/intoxication
-neuron toxin
-Spore former (can survive cooking)
-Botulinum toxin (heat labile), cosmetic application
Number of cases, Symptoms and Treatment for Clostridium botulinum
-Few cases, but high mortality
-Paralysis (18-24 hours), can last for months
-Treatment = ventilation and antitoxin
Is the US good at food safety?
-Yes
What is Clostridium botulinum: Infant botulism?
-Grows in intestines
-often from honey, can be environmental
-due to immature immune system and immature intestinal flora
-Hypotonia
Hyptonia
-floppy head syndrome
-decreased muscle tone
What is the treatment for Clostridium botulinum: Infant botulism
-Treatment = ventilation and tube feeding
-Self-limiting 3-6 weeks
Salmonella enterica
-Typhimurium = odd
-eggs, meat, dairy products
-enterocolitis
-live bacteria shed for several weeks
-cells grow inside phagocyte and spread to other cells
-self-limiting
What type does Salmonella enterica produce?
-produce endo, exo, and enterotoxins
Enteroclitis
-headache, chills, vomiting, diarrhea, and fever for 8-48 hours
Salmonella enterica subtype Typhi
-causes Typhoid fever
-15% mortality when untreated
Types of Escherichia coli
-Enterohemorrhagic (EHEC)(O157:H7)
-Enterotoxigenic (ETEC)
-Enteropathogenic (EPEC)
-Enteroinvasive (EIEC)
Enterohemorrhagic (EHEC)(O157:H7)
-verotoxin
-Hemorrhagic/bloody diarrhea, kidney failure
-Undercooked (ground) meat
-Jack in the box out break 1991
-Recently, fresh fruits and vegetables contaminated with animal feces (cow) or water runoff from animal lots
Enterotoxigenic (ETEC)
-Enterotoxins (heat labile)
-Traveler’s diarrhea (watery)
Heat labile
-sensitive or destroyed in heat
Enteropathogenic (EPEC)
-children
-non-invasive
-no toxins
Enteroinvasive (EIEC)
-Invasive, survives in phagocytes
-Watery to blood diarrhea
What is Campylobacter species caused by and what are its symptoms?
-caused by poultry, pork, shellfish, surface waters
-normal intestinal flora in chickens and turkeys
-Symptoms: diarrhea with watery/bloody stool, sterility, and abortions in animals
-high fever, headache, malaise, nausea, cramps
How much bacteria is need to infect for Campylobacter species and what does it infect?
-10^4 bacteria required for infection
-Self-limiting 7-10 days
-invades intestinal epithelium, causes inflammation
-Number one bacterial food poisoning
Listeria monocytogenes
-found in many water and soil samples, contamination during food processing
-acid and salt tolerant, psychrotolerant
-meat, diary, fresh produce
-most infections are minor and not even recognized
-acute rare, but deadly
-infects developing fetas, 90% mortality rate
psychrotolerant
cold tolerant
What does Listeria monocytogenes do?
-intracellular pathogen
-polymerizes host cell actin to drive motility, breaks from one cell into another
What rare diseases come from Listeria monocytogenes?
-Bactermia
-Meningitis
Norovirus
-RNA virus
-Stomach flu or viral gastroenteritis
-fever, chills, headache, muscle aches
-self limiting = 1-2 days
-highly contagious and passed via contact with infected people or contaminated surfaces or food
-cruise ships
What are the top five factors that contribute to foodborne disease outbreaks in the US?
-Inadequate refrigeration (47%)
-Food prepared to far in advance (21%
-Infected person with poor personal hygiene (21%)
-Inadequate cooking (16%)
-Inadequate holding temperature (16)
