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VSCI200 PHEW > Food born diseases > Flashcards

Food born diseases Flashcards

1
Q

describe a few ways in which food used to be preseved

A

salted; dried; vinegar; sugared

cool caves; smoked;fermented

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2
Q

Name some times in food processing where it may become contaminated

A

primary production, slaughterhouse, storage conditions, bacteriocidal step taken at all

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3
Q

Name 2 types of ‘goof’ bacteria, with regard to food microbiology

A

probiotics

fermentation agents

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4
Q

There are 4 phases of bacterial growth; name them

A
  1. lag
  2. log
  3. stationary (depletion of nutrients and accum of toxic products. prolif = death
  4. death
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5
Q

what is the D-value

A

time req to destroy 90% of bacterial population at a given temperature

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6
Q

what is the Z-value

A

number of degrees req for the D value to decrease by 1 log cycle (10x)

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7
Q

Name 3 bacteria who’s D60

A

Salmonella; Campy; Enterococcus faecalis

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8
Q

what is the D value for clostridium botulinum spores

A

D100

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9
Q

Does substrate of the feedstuff have an effect on D value

A

Yes!

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10
Q

name 3 main factors that affect microbial growth

A

intrinsic - properties of the food
extrinsic - storage
implicit - properties of the MO

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11
Q

name some intrinsic factors

A

nutrients available for MOs; pH; buffering capability; redox potential

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12
Q

what is the preffered pH range for MOST bacteria?

A

6-8

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13
Q

what is the prefered pH for most yeasts?

A

4.5-6

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14
Q

what is the natural pH of meat

A

5.6 - perfect range for most things!

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15
Q

Name a alkali tolerant bacteria

A

Vibrio (Cholera)

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16
Q

Name a acidic tolerant bacteria

A

Lactobacilli

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17
Q

what is redox potential (Eh)

A

tendancy for the medium to accept or donate electrones

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18
Q

what type bacteria like high redox potential mediums

A

obligate aerobes (pseudomonas)

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19
Q

Obligate anaerobes like low redox potentials, name one

A

clostridia

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20
Q

Name a food product with a:
A) high Eh
B) low Eh

A

A) lemon and raw meat

B) cooked meat

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21
Q

HIgh water activity can increase ability of bacteria to proliferate. NAme a few ways to reduce this

A

dry
add salt (NaCl)
freeze

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22
Q

What type of bacteria like high NaCl concentrations

A

Halophilic MOs

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23
Q

What are Xerophillic MOs good at

A

growing in dry places

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24
Q

Name some natural antimicrobial factors found in food

A

ovotransferrin (egg white)
Lactoferrin
egg shell
nitrites (added to meat for red-ness) - inhib C.botul

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25
Q

What colour mould does penecillin give

A

blue

26
Q

name a bacteria which only affects the surface of the meat

A

sporotrichum carnis

27
Q

Why is CO2 and N2 used in meat packagings

A

to inc pH
red surface contamination
red enzyme availability to prevent bdown

28
Q

What does facultative anaerobe mean

A

it can grow in both aerobic and anaerobic conditions

29
Q

What temperatures are thermophiles (clost botul) happy in?

A

40-90

30
Q

What are the 2 types of bacteria important in the preserving food

A

mesophiles
psychrotrophs
- both grow at temp most food stored at (inc fridge)

31
Q

What environment does Salmonella like?

A

aerobic
low pH
low water avail

32
Q

What does Staffy A like?

A

aerobic
low pH
VERY low water avail

33
Q

What environ does E coli like?

A

Aerobic and v low pH but high water

34
Q

What environment does LIsteria monocytogenes like?

A

v low temperature and very high O2 and water availability

35
Q

What temperature must a freezer reach before no MO can grow?

A

-12+ and rapidly is best

36
Q

Name some of the implicit factors affecting bacterial growth

A

growth rate
mutalism
antagonism (lactobac and paths)
adaptation and competition

37
Q

What is the stress response of bacteria (60% of the Salmonella genome!)

A

a change in the environment (temp change etc) causes a response from the bacteria

  • fast growing
  • virulent
  • resistant
  • adaptable
38
Q

Name 6 gram negative bacteria which cause food born diseases

A 
Salmonella
Campy
E coli
Shigella
Yersinia enterocolitica
Vibrio spp
39
Q

Name 5 gram positive food born pathogens

A 
listeria monocytogenes
staffy a
clost perffringens
clost botulinum
bacillus cereus
40
Q

What are the 2 types of food born infection

A
  1. Toxico-infection

2. INvasive infection

41
Q

Name the 2 toxins types which can cause toxicoinfectionsq

A

entero

neuro

42
Q

name the 2 types of invasive infection

A

enteric

systemic

43
Q

What is foodborn intoxication?

A

when host ingests toxins/toxic metabolites the bacteria had produced in the food

44
Q

Name a pathogen which causes intoxication in adults

A

C. botulinum

45
Q

What syndrome does B cereus cause

A

emetic syndrome

46
Q

what type of toxin does staff a produce?

A

thermostable enterotoxin

47
Q

describe what an invasive infection actually is

A

when bacteria is ingested and it penetrates intestinal mucosa. it can be local or systemic

48
Q

describe what a toxicoinfection actually is

A

bacteria is ingested and the organism produces toxins in the GIT

49
Q

Name 3 bacteria which cause invasive infections

A

Campy
Salmonella
Listeria mono

50
Q

Name 5 bacteria which cause toxicoinfections

A 
E coli
Vibrio
C perfring
B cereus
C botulinum
51
Q

What gram negative bacteria involved in food born disease are not facultative anaerobes

A

campy - micro-aerophillic

52
Q

what agar type is used to isolate entericobacteria

A

MacConkey

- lactose fermenting –> pink; other stay orange

53
Q

Name an agar selective for Salmonella

A

Brilliant green

salmon –> red

54
Q

Name an agar selective for E coli

A

EMB

55
Q

Name an agar selective for CAmpy

A

blood agar under reduced oxygen tension conditions

56
Q

What serotypes are different in salmonella and e coli?

A

antigen K which is for capsule. not in salmonella

57
Q

how do you subtype salmonella?

A

phage-typing. put bacteria against different lytic enzymes

58
Q

Name the 5 types of E coli enteric infection

A

Entero __________ E. coli

  1. pathogenic
  2. toxigenic
  3. invasive
  4. haemorrhagic
  5. aggregative
59
Q

what properties of E coli allow UTI

A

capsule
pili
fibriae

60
Q

what is the most serious toxin

A

shiga-like toxins –> destroy b vessels

VSCI200 PHEW (4 decks)

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