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Food-Borne Pathogens > Molds > Flashcards

Molds Flashcards

1
Q

What is a mycotoxin

A

A fungal metabolite that when ingestion, inhaled or absorbed, cause disease

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2
Q

Mycotoxin production occurs only as a result of…

A

Fungal growth (not the presence of spores)

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3
Q

Toxicity due to mycotoxins is…

A

Cumulative of a long period of time

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4
Q

5 mycotoxins discussed in class

A

Aflatoxins, ochratoxin A, fumonisins, deoxynivalenol, zearalenone

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5
Q

Symptoms of aflatoxicosis

A

Jaundice, fever, vomiting and anorexia

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6
Q

4 naturally occurring aflatoxins

A

B1, B2, G1, G2

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7
Q

How are aflatoxins named

A

Based on their fluorescence under UV light

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8
Q

What happens when aflatoxins are eaten by lactating cows

A

They are excreted as aflatoxins M1 and M2

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9
Q

What are two organisms that produce aflatoxins important in food

A

Aspergillus flavus and parasiticus

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10
Q

What is the growth temp and Aw of A. flavus

A

T: 10-48C
Aw: depends on temp (decreases with increasing temp)

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11
Q

How can A. flavus be destroyed

A

Pasteurization

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12
Q

Where is A. flavus found

A

Common in food crops in tropical and warm areas (peanuts, corn, tree nuts)

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13
Q

Where is A. parasiticus found

A

More associated with peanuts (more geographically limited than A. flavus)

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14
Q

What is a prereq for high aflatoxin levels in peanuts

A

Aspergillus infection while the nuts are still in the ground

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15
Q

What contributes to pre-harvest Aspergillus infection in peanuts

A

High spore numbers, drought, high soil temp

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16
Q

Control strategies for Aspergillus

A

Crop rotation, irrigation, biocontrol (inoculating fields with non-toxic strains so they compete with each other)

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17
Q

3 methods for removal of aflatoxin by heat and their effectiveness

A
  1. Boiling/autoclaving - less than 25%
  2. Dry roasting - up to 80%
  3. Alkali process (peanut oil) - 100%
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18
Q

5 primary toxic effects of aflatoxin

A

Acute toxicity, liver carcinogenicity, liver cirrhosis, immunosuppression, growth retardation in children

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19
Q

What is the relation between hepatitis B and aflatoxin

A

If you have hep B, you are 30 times more likely to develop liver cancer

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20
Q

How does aflatoxin cause liver cancer

A

NEED to have consumption of low levels over long period of time

  1. Liver enzymes convert aflatoxin to epoxide
  2. Epoxide binds liver proteins and causes liver failure
  3. Epoxide binds DNA and is precursor for liver cancer
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21
Q

What part of the immune system does aflatoxins suppress

A

Cell-mediated immune response

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22
Q

3 effects of immunosuppression by aflatoxin

A
  1. Decrease phagocytic activity of macrophages
  2. Increased susceptibility to infection
  3. Reduced response to vaccines
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23
Q

What is the acceptable safe level of consumption of aflatoxin in humans

A

15ug/kg

24
Q

What 3 groups of fungi produce ochratoxin A

A
  1. Ocher-color aspergilli
  2. Black aspergilli
  3. Penicillium
25
Q

What does OTA do

A

Is a nephrotoxin that affects kidney function and has carcinogenic properties

26
Q

How can you tell if someone has ingest OTA

A

Blood test, it has a long half life (3 weeks) in the blood

27
Q

What is the mechanism of OTA

A

Unclear, likely related to phenylalanine metabolism

28
Q

What are people in NA exposed to OTA from (fungi and products)

A

Penicillium verrucosum

Products include barely, wheat, coffee, wine, beer

29
Q

Where are OTA levels low

A

Tropical and subtropical regions

30
Q

What is the tolerable weekly intake of OTA

A

100ng/kg

31
Q

What control method prevents OTA production

A

Rapid drying (hard to do)

32
Q

What is a known fungi that produces OTA in wine

A

A. carbonarius

33
Q

4 control methods to prevent A. carbonarius growth in grapes

A
  1. Proper irrigation
  2. Air flow
  3. Crop covers
  4. Fungiside applications
34
Q

What can lead to OTA formation in coffee beans

A

Slow drying

35
Q

What can control OTA production in coffee beans

A

Effective sun drying or mechanical dehydration

36
Q

What fungi produces fumonisins

A

Fusarium verticilloides and F. proliferatum

Also A. niger

37
Q

Where are fusarium species always present

A

On corn and sorghum

38
Q

A. niger is associated with fumonisins in…

A

Grapes, raisins and coffee

39
Q

What is a concern of A. niger producing fumonisins

A

It can also produce OTA, and the co-occurrence of the two would be bad

40
Q

How do Fusarium colonized kernels start showing mycotoxin symptoms

A

When the plant is stressed (drought, heat of insect predation), it leads to a disease-mycotoxin producing interaction

41
Q

What do fumonisins do

A

They affect sphingolipid metabolism, cause depletion of complex sphingolipids and this interferes with the function of some membrane proteins (inhibition of folate binding)

42
Q

What does fumonisins cause in humans

A

Esophageal cancer and neural tube defects, like spina bifida in infants

43
Q

How can you prevent fungal growth in corn

A

Rapid drying (cannot live below Aw 0.9)

44
Q

What is mixtamalization

A

A process where the corn is soaked and cooked in an alkaline solution to remove almost fumonisins

45
Q

If a product is processed above __, fumonisins levels are decrease

A

150C

46
Q

What fungi produce deoxynivalenol (DON)

A 
Fusarium graminearum (some)
Fusarium culmorum (all)
47
Q

Where is F. culmorum found

A

Small grains (wheat and barely)

48
Q

What is the action of DON

A

Inhibits protein synthesis

49
Q

Where is DON production on corn the highest

A

Cooler, wet climate (like canada)

50
Q

What is a safe level of consumption of DON in human and bovine feeds

A

Human: 1mg/kg
Bovine: 10mg/kg

51
Q

What are some control methods for DON

A

Fungicides, crop rotation, forecasting symptoms (to warn producers)

52
Q

What activity does zearalenone have in pigs, cattle and sheep

A

Estrogenic activity

53
Q

What are symptoms of ZEA in pigs

A

Vulvovaginitis and vaginal rectal prolapse

54
Q

What fungi produce ZEA

A

Same fusarium species that produce DON, F. graminearum and F. culmorum (generally under same conditions)

55
Q

4 toxic effects of ZEA

A

Hepatotoxic, hematotoxic, immunotoxic, genotoxic

56
Q

What are the 3 mold genera most commonly associated with food

A

Aspergillus, penicillum and fusarium

Food-Borne Pathogens (14 decks)

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