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Food born diseases Flashcards

(60 cards)

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
What colour mould does penecillin give
blue
26
name a bacteria which only affects the surface of the meat
sporotrichum carnis
27
Why is CO2 and N2 used in meat packagings
to inc pH red surface contamination red enzyme availability to prevent bdown
28
What does facultative anaerobe mean
it can grow in both aerobic and anaerobic conditions
29
What temperatures are thermophiles (clost botul) happy in?
40-90
30
What are the 2 types of bacteria important in the preserving food
mesophiles psychrotrophs - both grow at temp most food stored at (inc fridge)
31
What environment does Salmonella like?
aerobic low pH low water avail
32
What does Staffy A like?
aerobic low pH VERY low water avail
33
What environ does E coli like?
Aerobic and v low pH but high water
34
What environment does LIsteria monocytogenes like?
v low temperature and very high O2 and water availability
35
What temperature must a freezer reach before no MO can grow?
-12+ and rapidly is best
36
Name some of the implicit factors affecting bacterial growth
growth rate mutalism antagonism (lactobac and paths) adaptation and competition
37
What is the stress response of bacteria (60% of the Salmonella genome!)
a change in the environment (temp change etc) causes a response from the bacteria - fast growing - virulent - resistant - adaptable
38
Name 6 gram negative bacteria which cause food born diseases
``` Salmonella Campy E coli Shigella Yersinia enterocolitica Vibrio spp ```
39
Name 5 gram positive food born pathogens
``` listeria monocytogenes staffy a clost perffringens clost botulinum bacillus cereus ```
40
What are the 2 types of food born infection
1. Toxico-infection | 2. INvasive infection
41
Name the 2 toxins types which can cause toxicoinfectionsq
entero | neuro
42
name the 2 types of invasive infection
enteric | systemic
43
What is foodborn intoxication?
when host ingests toxins/toxic metabolites the bacteria had produced in the food
44
Name a pathogen which causes intoxication in adults
C. botulinum
45
What syndrome does B cereus cause
emetic syndrome
46
what type of toxin does staff a produce?
thermostable enterotoxin
47
describe what an invasive infection actually is
when bacteria is ingested and it penetrates intestinal mucosa. it can be local or systemic
48
describe what a toxicoinfection actually is
bacteria is ingested and the organism produces toxins in the GIT
49
Name 3 bacteria which cause invasive infections
Campy Salmonella Listeria mono
50
Name 5 bacteria which cause toxicoinfections
``` E coli Vibrio C perfring B cereus C botulinum ```
51
What gram negative bacteria involved in food born disease are not facultative anaerobes
campy - micro-aerophillic
52
what agar type is used to isolate entericobacteria
MacConkey | - lactose fermenting --> pink; other stay orange
53
Name an agar selective for Salmonella
Brilliant green | salmon --> red
54
Name an agar selective for E coli
EMB
55
Name an agar selective for CAmpy
blood agar under reduced oxygen tension conditions
56
What serotypes are different in salmonella and e coli?
antigen K which is for capsule. not in salmonella
57
how do you subtype salmonella?
phage-typing. put bacteria against different lytic enzymes
58
Name the 5 types of E coli enteric infection
Entero __________ E. coli 1. pathogenic 2. toxigenic 3. invasive 4. haemorrhagic 5. aggregative
59
what properties of E coli allow UTI
capsule pili fibriae
60
what is the most serious toxin
shiga-like toxins --> destroy b vessels