Food born diseases

Question 1

describe a few ways in which food used to be preseved

Answer 1

salted; dried; vinegar; sugared

cool caves; smoked;fermented

Question 2

Name some times in food processing where it may become contaminated

Answer 2

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

Question 3

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

Answer 3

probiotics

fermentation agents

Question 4

There are 4 phases of bacterial growth; name them

Answer 4

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

Question 5

what is the D-value

Answer 5

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

Question 6

what is the Z-value

Answer 6

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

Question 7

Name 3 bacteria who’s D60

Answer 7

Salmonella; Campy; Enterococcus faecalis

Question 8

what is the D value for clostridium botulinum spores

Answer 8

D100

Question 9

Does substrate of the feedstuff have an effect on D value

Answer 9

Yes!

Question 10

name 3 main factors that affect microbial growth

Answer 10

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

Question 11

name some intrinsic factors

Answer 11

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

Question 12

what is the preffered pH range for MOST bacteria?

Answer 12

6-8

Question 13

what is the prefered pH for most yeasts?

Answer 13

4.5-6

Question 14

what is the natural pH of meat

Answer 14

5.6 - perfect range for most things!

Question 15

Name a alkali tolerant bacteria

Answer 15

Vibrio (Cholera)

Question 16

Name a acidic tolerant bacteria

Answer 16

Lactobacilli

Question 17

what is redox potential (Eh)

Answer 17

tendancy for the medium to accept or donate electrones

Question 18

what type bacteria like high redox potential mediums

Answer 18

obligate aerobes (pseudomonas)

Question 19

Obligate anaerobes like low redox potentials, name one

Answer 19

clostridia

Question 20

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

Answer 20

A) lemon and raw meat

B) cooked meat

Question 21

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

Answer 21

dry
add salt (NaCl)
freeze

Question 22

What type of bacteria like high NaCl concentrations

Answer 22

Halophilic MOs

Question 23

What are Xerophillic MOs good at

Answer 23

growing in dry places

Question 24

Name some natural antimicrobial factors found in food

Answer 24

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

Question 25

What colour mould does penecillin give

Answer 25

blue

Question 26

name a bacteria which only affects the surface of the meat

Answer 26

sporotrichum carnis

Question 27

Why is CO2 and N2 used in meat packagings

Answer 27

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

Question 28

What does facultative anaerobe mean

Answer 28

it can grow in both aerobic and anaerobic conditions

Question 29

What temperatures are thermophiles (clost botul) happy in?

Answer 29

40-90

Question 30

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

Answer 30

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

Question 31

What environment does Salmonella like?

Answer 31

aerobic low pH low water avail

Question 32

What does Staffy A like?

Answer 32

aerobic low pH VERY low water avail

Question 33

What environ does E coli like?

Answer 33

Aerobic and v low pH but high water

Question 34

What environment does LIsteria monocytogenes like?

Answer 34

v low temperature and very high O2 and water availability

Question 35

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

Answer 35

-12+ and rapidly is best

Question 36

Name some of the implicit factors affecting bacterial growth

Answer 36

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

Question 37

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

Answer 37

a change in the environment (temp change etc) causes a response from the bacteria - fast growing - virulent - resistant - adaptable

Question 38

Name 6 gram negative bacteria which cause food born diseases

Answer 38

``` Salmonella Campy E coli Shigella Yersinia enterocolitica Vibrio spp ```

Question 39

Name 5 gram positive food born pathogens

Answer 39

``` listeria monocytogenes staffy a clost perffringens clost botulinum bacillus cereus ```

Question 40

What are the 2 types of food born infection

Answer 40

1. Toxico-infection | 2. INvasive infection

Question 41

Name the 2 toxins types which can cause toxicoinfectionsq

Answer 41

entero | neuro

Question 42

name the 2 types of invasive infection

Answer 42

enteric | systemic

Question 43

What is foodborn intoxication?

Answer 43

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

Question 44

Name a pathogen which causes intoxication in adults

Answer 44

C. botulinum

Question 45

What syndrome does B cereus cause

Answer 45

emetic syndrome

Question 46

what type of toxin does staff a produce?

Answer 46

thermostable enterotoxin

Question 47

describe what an invasive infection actually is

Answer 47

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

Question 48

describe what a toxicoinfection actually is

Answer 48

bacteria is ingested and the organism produces toxins in the GIT

Question 49

Name 3 bacteria which cause invasive infections

Answer 49

Campy Salmonella Listeria mono

Question 50

Name 5 bacteria which cause toxicoinfections

Answer 50

``` E coli Vibrio C perfring B cereus C botulinum ```

Question 51

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

Answer 51

campy - micro-aerophillic

Question 52

what agar type is used to isolate entericobacteria

Answer 52

MacConkey | - lactose fermenting --> pink; other stay orange

Question 53

Name an agar selective for Salmonella

Answer 53

Brilliant green | salmon --> red

Question 54

Name an agar selective for E coli

Answer 54

EMB

Question 55

Name an agar selective for CAmpy

Answer 55

blood agar under reduced oxygen tension conditions

Question 56

What serotypes are different in salmonella and e coli?

Answer 56

antigen K which is for capsule. not in salmonella

Question 57

how do you subtype salmonella?

Answer 57

phage-typing. put bacteria against different lytic enzymes

Question 58

Name the 5 types of E coli enteric infection

Answer 58

Entero __________ E. coli 1. pathogenic 2. toxigenic 3. invasive 4. haemorrhagic 5. aggregative

Question 59

what properties of E coli allow UTI

Answer 59

capsule pili fibriae

Question 60

what is the most serious toxin

Answer 60

shiga-like toxins --> destroy b vessels