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Microbiology PMY 3 > Food Microbiology > Flashcards

Food Microbiology Flashcards

1
Q

Describe microbial interaction and food

A

Food is rarely, if ever sterile

Microbial associations - most times no discernible effect

However, some instances m
Can cause spoilage, food-borne disease (food poisoning) and be beneficial

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2
Q

What is the economic problem of food spoilage?

A
  • not of quality expected by consumer (quality, NOT spoilage)
  • undesirable growth of microbes
  • production of volatile compounds (metabolism)
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3
Q

What are possible causes of food spoilage?

A
  • insect damage
  • physical injury (bruising, pressure, freezing, drying and radiation )
  • activity of indigenous enzymes
  • naturally occurring chemical changes
  • Activity of bacteria, yeasts and moulds
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4
Q

What is the shelf life of food?

A

The time during which it remains stable and retains its desired qualities

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5
Q

What are the classifications of food spoilage?

A

Perishable- fresh fruits, fish, meats

Semi-perishable- eggs, onions, potatoes, carrots, beans

Non-perishable - flour, cereal

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6
Q

What factors influence microbial growth ?

A

Intrinsic- inherent to the food:

  • pH
  • moisture content(water activity)
  • Redox potential
  • nutrient content
  • antimicrobial constituent
  • biological structures

Extrinsic- environmental factors
-Temperature of storage

-Composition of gases and relative humidity in the atmosphere surrounding the food

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7
Q

What are the basic principles of food preservation?

A
  • to slow down activity: spoilage/disease-causing microbes

- to kill all microbes

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8
Q

What processes are used in food preservation?

A
  • Drying
  • smoking
  • freezing
  • Vacuum packing
  • salt
  • sugar
  • pickling
  • Cranning and bottling
  • irradiation
  • modified atmosphere
  • biological processes

Think of these as methods of preventing or eliminating microbial growth

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9
Q

What is food fermentation?

A

This is the process of converting carbs to alcohol or organic acids using microorganisms-yeasts or bacteria - under anaerobic conditions

Positive interaction: microbes+food

  • anaerobic catabolism of organic compounds
  • lactic acid Bacteria
  • acetic acid Bacteria
  • yeast (Saccharonyces cerevisiae)
  • Mold (aspergillus)
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10
Q

What cultures are used for dairy products?

A

Starter cultures:
-lactic acidosis Bacteria (lactobacillus, leuconostoc, lactococcus, pediococcus, streptococcus)

Second inoculum:

-Propionibacterium (Swiss cheese), peniccillium roqueforti(blue cheese)

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11
Q

What is the function of microbes in meat products?

A

Nitrate converted to nitrite: Micrococcus, staph, xylosus, staph. carnosus

  • improve flavor: micrococcus
  • increase acidity. (Lowering pH): pediococcus and lactobacillus
  • mound growth: penicillium nalgiovense (desired in some Italian salamis)
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12
Q

Give examples of meat products. How are they process differently ?

A

Sausage: pork/beef+salt+ seasonings

  • salami, pepperoni, bolognas
  • process different in North America and Europe
    • America: rapid, high temps(sour tasting)
    • Europe: slow, lower temps(no sour taste)
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13
Q

Why is food safety a major source of concern, according to CDC?

A

CDC estimates in the US:

  • 1 in 6 Americans get sick from contaminated foods or beverages each year
  • 128,000 hospitalized
  • 3,000 die (children/ elderly/immunocompromised)
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14
Q

Why is food safety a major source of concern, according to the USDA?

A

The United States department of agricultural estimates that foodborne illnesses cost more than 15.6 billion dollars each year

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15
Q

Why is food safety(food Borne diseases) a major source of concern?

A
  • changes in demographics
  • changes in food preferences
  • changes in food processing/production
  • changes in food distribution
  • microbial adaptation
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16
Q

Give the general epidemiology of food borne diseases

A

Sex- equally affects both men and women

Age- all at risk, highest incidence: infants/pre-school, elderly, immunocompromised

Seasonal incidence:

  • outbreak in warmer months.
    • salmonella:summer/early autumn
    • campylobacter spp. : late spring/ early summer.
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17
Q

What are the 2 major categories of food borne diseases ?

A
  1. Food poisoning

2. Food-borne infection

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18
Q

Explain food poisoning as a category of food borne diseases

A

AKA: food-borne intoxication, food toxemia

Consumption of food containing preformed toxins
-enterotoxins, neurotoxins

Usually bacterial: S. aureus, B. cereus, C. botulinum

Occasional fungi: mushroom-amantia

Occasional algae: -ciguatera

Not an infection

Usually rapid onset(mins hrs)
-exception C. botulinum (hrs-days)

Short duration(24. Hrs)

May be fatal

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19
Q

Explain food-borne infections as a category of food-borne infection

A

Consumption of food containing microbe
-(food acts as vehicle for entry)

  • bacterial: C. Jejuni, salmonella, shigella, E. coli, V. parahaemolyticus
  • Viral: norovirus
  • protozoan: C. Parvum, C. cayetanenisis

Longer incubation:

  • 1st colonization
  • damage: toxin production, invasion
  • longer duration
  • may be fatal
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20
Q

What is the mode of transmission of staphylococcus aureus?

A

Humans are the main reservoirs

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21
Q

What are the microbial characteristics of staphylococcus aureus ?

A
  • encapsulated gram positive, catalase positive cocci
  • coagulase positive
  • B-hemolytic on blood agar plate
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22
Q

What is the epidemiology of staphylococcus aureus ?

A
  • typically infected food handler

- about 50% humans carry staphylococci

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23
Q

What is the pathogenicity of staphylococcus aureus?

A
  • enterotoxins
  • heat stable, acid stable

-incubation: under 6 hours of ingestion caused by pre-formed toxin

  • Nausea, vomitting, watery diarrhoea, dehydration
    • duration: less than 48 hours

-implicated foods: bakery products, cooked meats, fruit and vegetables

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24
Q

What are the microbiological characteristics of bacillus cereus?

A

-obligate aerobe, spore forming gram positive rods, arranged singularly or in pairs

  • produces toxins: neurotoxins
    • heat stable, acid stable
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25
Q

What is the mode of transmission of bacillus cereus?

A

-ubiquitous organism of the soil: commonly found in low levels in raw, dried, and processed foods

  • ingestion of foods kept at ambient conditions after cooking
    • incubation: under 4 hours of ingestion
      • nausea, vomitting
    • duration: under 24 hrs
  • easy cross-contamination
    • air, soil, water and dust
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26
Q

Describe bacillus cereus food poisoning pathogenicity

A

Pathogenicity:

  • opportunistic pathogen
  • Intoxication characterized by two forms:
    • An emetic form with severe nausea and vomiting- linked primarily to fried rice, milk and pasta
    -A diarrheal form with abdominal cramps and diarrhea- linked primarily to meat dishes and sauces

Implicated foods: cooked rice and pulses (beans, lentils, etc.)

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27
Q

What are the microbial characteristics of C. botulinum?

A

Gram positive (at least in early stage of growth), anaerobic, spore-forming bacillus

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28
Q

Explain the mode of transmission of C. botulinum food poisoning

A
  • adult botulism, caused by ingestion of preformed toxin in food
  • infant botulism, in which the organism replicates and secretes toxin in the intestinal tract
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29
Q

Give the epidemiology of C. botulinum food poisoning

A

Sporadic

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30
Q

Explain the pathogenicity of C. botulinum food poisoning

A

Pathogenicity :

  • neurotoxins: Heat labile
  • incubation: 18-36 hours of ingestion
    • initial: nausea, vomiting, abdominal pain, diarrhoea
  • Characteristics: symmetrical descending flaccid paralysis
  • fatal: within 24 hours
  • mortality rate : 10-20%
  • typically: home canning practices
  • easy cross-contamination
    • air, soil, water and dust
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31
Q

Explain ciguatera as a marine associated food poisoning

A

Ciguatera: Gambierdiscus toxicus (Algae)
-Baracuda, grouper, amberjacks

-neurotoxin: ciguatoxin

  • incubation: 3-6 hours
    • nausea, abdominal pain, watery diarrhea
32
Q

Explain Scombroid as a marine associated food poisonings

A

Scombroid: Non-allergic histamine

  • bacteria: Stenotrophomonas maltophilia, M. morganii
    • histidine —> histamine (scombrotoxin)
    -tuna, Mahi-mahi, marlin
  • incubation : mins- 3 hrs
    • watery diarrhoea, nausea, metallic taste
33
Q

Explain the pathogenicity of Algae

A

Neurotoxic: Karelia brevis (Brevitoxins )

Paralytic: Alexandria spp., Gymnodinium catenatum, Pyrodinium bahamense, Gonyaulax spp. (Saxitoxins)
-short incubation: under 1-3 hours

  • mouth numbness, tingling in extremities, GI upset(Brevetoxins)
  • duration
34
Q

Explain the epidemiology of Campylobacter spp.

A

Worldwide importance because of djarrheal disease

C. jejuni- 90% of cases
C. coli- most of the 10%

35
Q

What is the most of transmission of campylobacter spp.?

A

Mode of transmission:

Ingestion of organisms in undercooked food, contaminated water, and raw milk

36
Q

What are the microbial characteristics of campylobacter Sp.?

A

Gram negative spiral and S -shaped bacteria; darting motility; microaerophilic; will grow only under reduced oxygen tension; optimal growth temperature is at 42 C

Examples: C. jejuni, C. fetus (sterility/ spontaneous abortion- sheep/cattle)

37
Q

Explain the pathogenicity of campylobacter spp.?

A
  • acute enteric disease of variable severity;diarrhea, abdominal pain, malaise, fever, nausea and vomiting; prolonged illness in up to 20% of patients
  • incubation: 3-5 days

Watery-bloody diarrhoea, abdominal pain, fever(invasive)

-duration: 1 week

  • intestinal tract of wide variety of wild and domestic animals (zoonotic)
    • commercially raised poultry
    • normal commensal of cows
    • long-term commensal of sheep
    • Pigs( carriers of C. coli)
    • C. jejuni intestinal commensal cats and dogs
38
Q

What is the number 1 bacterial cause of food-borne disease US?

A

Campylobacter spp.

39
Q

What are the microbial characteristics of salmonellosis?

A

Salmonella enteritica subspecies enteric serotype xxx

Characteristics:
Gram-negative, flagellated facultatively anaerobic bacilli characterized by O, H an Vi antigens.

-there are over 1800 known serovars which current classification considers to be separate species

40
Q

Explain the pathogenicity of salmonellosis

A

Gastrienterritis: S. Typhimurium, S. Enteritidis, S. Newport

- incubation: 8-48 hours
- duration: 2-3 days
- nausea, vomitting, watery/bloody diarrhea
  1. Septicemia/Bacteremia(focal infection): rare, S. Cholerasuis
  2. Enteric fever (typhoid and paratyphoid fever): S. Typhi, S. Paratyphi
    • most severe
41
Q

Discuss the mode of transmission of salmonellosis

A

The fecal-oral route and can be transmitted by food and water, by direct animal contact, and rarely from person-to-person

High risk groups- infants and immunocompromised individuals

42
Q

What are possible sources of salmonellosis infection?

A
  • Food(poultry, eggs, meat)
  • water
  • contact with animals
  • vegetables with human or animal waste fertilizer
43
Q

What are the microbial characteristics of E. coli?

A

Gram-negative, facultative anaerobic, Rod-shaved, coliforms bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blood organisms

Catalase positive, oxidase negative

-lactose fermenter

44
Q

What is the mode of transmission of E. coli?

A

-cattle and other ruminant animals are the main carriers

45
Q

Explain the complex pathogenicity of E. coli

A

Strain: EHEC- E. coli O 157:H7

  • non-invasive, verotoxin: similar time shiga toxin (shig. Dysenteriae)
  • Inhibits protein synthesis in host cell
  • SMAC -sorbitol MacConkey Agar- recommenced for the detection of E. coli O157: H7 which ferments lactose but doesn’t ferment sorbitol, produces colorless to pale yellow colonies in the presence of neutral pH indicator

Incubation: 3-7 days

Symptoms:

  • watery-bloody diarrhoea,
  • haemolytic uremic syndrome (HUS)
  • thrombic thrombocytopenia purapura(TTP)

Duration: 1 week

Implicated foods: raw meat and salad greens

46
Q

What are the OTHER types of E. coli?

A

ETEC: enterotoxic E. Coli

EPEC: enteropathogenic E. Coli

EIEC: Enteroinvasive E. Coli

EAEC: Enteroadherent E. coli

47
Q

What is ETEC: enterotoxic E. Coli?

A

ETEC: enterotoxic E. Coli

  • noninvasive, enterotoxin
  • causes: traveller’s diarrhoea: profuse watery diarrhea
48
Q

What is EPEC: enteropathogenic E. Coli?

A

EPEC: enteropathogenic E. Coli
-Non-invasive, no toxin production, effaced microvilli

-causes: watery diahrrea in children in developing countries

49
Q

What is EIEC: Enteroinvasive E. Coli?

A

EIEC: Enteroinvasive E. Coli

  • invasive, no toxin production
  • causes: bloody diarrhoea similar to shigellosis
50
Q

What is EAEC: Enteroadherent E. coli?

A

EAEC: Enteroadherent E. coli

  • possible toxin production, no invasion
  • causes: bloody diahrrea
51
Q

Discuss the microbial characteristics of listeria monocytogenes

A
  • gram-positive, non-spore forming, and catalase positive bacilli
  • narrow ring of B- hemolytic
  • cold growth
  • aerobic/facultative anaerobic
52
Q

What is the mode of transmission of listeria monicytogenes?

A

-Consumption of contaminated food

53
Q

Discuss the pathogenicity of listeria monocytogenes

A

Pathogenicity:
-pathogenic bacterium which causes a group of diseases collectively known as listeriosis

  • mild form of gastrointestinal illness in healthy adults
  • May be serious for the very young, elderly, immunocompromised individuals and pregnant women
54
Q

What are the sources of 8 fiction of listeria monocytogenes?

A
  • Raw meat
  • deli meats
  • ready to eat meat products
  • soft cheeses
  • unpasteurized
  • raw sprouts
  • chilled smoked seafood
55
Q

Why is listeria monocytogenes a major concern?

A
  • it’s ubiquitous nature
  • its ability to survive and grow at low temperatures, I.e. typical refrigeration temperature
  • the severity
  • the high case fatality rate
56
Q

What are the high risk groups of listeria monocytogenes?

A
  • extremely young
  • old
  • pregnant
  • immunocompromised
  • pregnant women 20X more likely to get listeriosis than any other population
    • spontaneous abortion , neonatal meningitis/sepsis

These high risk groups

  • have high mortality rate of 25-50%
  • and neurological sequelae as a result of bacterial meningitis.
57
Q

Which foods are susceptible to Ayers India enterocolytica? What can this cause?

A

Pork, lettuce

Invasive, causes watery/bloody diarrhea

58
Q

What foods are susceptible to vibrio parahaemolyticus? What can this cause?

A

Invasive

Causes watery/bloody diahrrea

59
Q

What foods susceptible to Bacillus cereus ? What can this cause?

A

Any foods

Nom-invasive, enterotoxin

Causes watery/bloody diahrrea(similar to C. Perfringens)

60
Q

What foods are susceptible of Clostridium perfringens? What does this lead to?

A

Various meats, gravy

Non-invasive, enterotoxin

Causes: watery diahrrea

61
Q

What are the foods that are susceptible to Shigella spp.? What can this lead to?

A

Any foods

Invasive, (shiga toxin for dysentry)

Causes watery-bloody diarrhea

62
Q

What is the norovirus?

A

Estimated 50% outbreaks of acute, non-bacterial gastroenteritis (USA)

  • Small (27 nm dia)
  • Non-enveloped, ss +ve sense RNA
  • Amorohous surface: feathery, ragged outline
63
Q

Discuss the pathogenicity of the norovirus

A
  • Older children and adults (Children under 5 yrs comeback in lecture )
  • incubation: 24-48 hrs, Duration: 24-60 hrs
  • Vomitting, abdominal cramps, myalgias, malaise, headache, nausea, low grade fever and 1-2 days diahrrea
64
Q

How can the norovirus be trans,otter?

A

Norovirus spreads when a person gets. Poop or vomit from an infected person in their mouth possibly Via

Providing care
Shaking hands
Changing diapers
Touching contaminated surfaces

Touching your mouth

65
Q

What are the microbial characteristics if vibrio cholerae?

A

Microbial characteristics:

  • gram-negative, highly motile curved rods with a single polar flagellum
  • Non lactose fermenter
  • Only two serogroups, O1 and O139, are responsible for all epidemic and endemic cholera
66
Q

What are the mode of transmission of vibrio cholerae?

A

Ingestion of water or food prepared with water containing V. cholerae

Fecal-oral transmission

  • water borne
  • poor hygiene
67
Q

Explain the pathogenicity 9f cholera

A

Is an extremely virulent disease that can cause severe acute watery diahrrea

Symptoms- 12 hours and 5 days for a person to show symptoms after ingesting contaminated food or water

Result: Profuse watery duahrrhea occurs (20-30 L/day)

“RICE WATER STOOL”

68
Q

What are the 5 key steps in prevention of food borne disease ?

A
  1. Keep clean
  2. Separate raw and cooked
  3. Cook thoroughly.
  4. Keep food at safe temperatures
  5. Use safe water and raw materials
69
Q

How to best keep a place and yourself clean?

A
  • wash your hands before handling food and often during food preparation
  • wash your hands after going to the toilet
  • wash and sanitize all surfaces and equipment used for food preparation
  • Protect kitchen areas and food from insects, pests and other animals
    • rats and mice
    • flies
    • cockroaches

-pests may carry pathogens and may also cause physical contamination of food with their droppings, eggs, fur and dead bodies

70
Q

What are behaviors that may contaminate foods?

A
  1. Scratching the scalp
  2. Running fingers through hair
  3. Wiping or touching the nose
  4. Rubbing an ear
  5. Touching a pimple or open sore
  6. Wearing a dirty uniform
  7. Coughing or sneezing into the hand
  8. Spitting in the establishment
    - Not washing after visiting the bathroom
71
Q

How can raw and cooked foods be separated?

A
  • food contaminated with pathogens from another source.
  • Separate raw meat, poultry and seafood from other foods
  • Use separate equipment and utensils such as knives and cutting boards for handling raw foods
  • Store food in containers to avoid contact between raw and prepared
72
Q

How can we ensure food is cooked thoroughly?

A
  • Cook food thoroughly, especially meat, poultry, eggs and seafood
  • bring foods like soups and stews to boiling to make sure
  • for meat and poultry, make sure that juices are clear, not pink. Ideally, use a thermometer
  • reheat cooked food thoroughly
  • Under ideal conditions, bacteria multiply rapidly between 5 degrees Celsius (41F) and 60 degreees Celsius (140F)

The danger zone for food

  • under 5C bacteria multiply slower
  • freezing does not kill bacteria
  • over 60C, most bacteria are killed (not endospore)
73
Q

What are the appropriate cooking temperatures?

A
  • Poultry, stuffed meats, and stuffed pasta: 73.9C(165F)
  • Ground beef and ground pork: 68.3C(155F)
  • Eggs, fish, and pork products: 62.7C (147F)
  • Reheat ALL foods (leftovers) to 73.9C(165F)
74
Q

How can foods be kelt at safe temperatures?

A
  • Do not leave cooked food at room temperature for more than 2 hours
  • Refrigerate promptly all cooked and perishable food (preferably below 5 degrees Celsius)
  • keep cooked food piping hot ( more than 60C) prior to serving
  • do not store food too long even in the refrigerator
  • Do not thaw frozen food at room temperature
75
Q

How to properly use safe water and raw materials ?

A
  • use safe water or treat it to make it safe
  • select fresh and wholesome foods
  • choose foods processed for safety, such as pasteurized milk
  • wash fruits and vegetables, especially if eaten raw
  • Do not use food beyond its expiry date

Microbiology PMY 3 (24 decks)

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