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Cell biology 1220 > Microbiology 4, 5, 6 > Flashcards

Microbiology 4, 5, 6 Flashcards

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1
Q

What is meant by chemorganotrophic microbes? What is their ideal growth medium?

A

Chemorganotrophic microbes = microbes that use organic compounds for energy

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2
Q

How many people suffer from food bourne illnesses per year?

A

1 million people suffer from foodbourne illnesses per year

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3
Q

What is the most common food poisoning?

A

Campylobacter = most common food poisoning

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4
Q

What is meant by pathogenicity?

What microbe has high pathogenicity?

A

The number of microbes needed to cause illness

Salmonella has high pathogenicity - large no. of microbes needed to cause illness

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5
Q

How do microbes cause illness?

A

Producing toxins - endotoxins and exotoxins

Producing toxic waste products

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6
Q

What are exotoxins? Give examples

A

Exotoxins = toxins released extracellulary e.g. enterotoxins, cytolytic toxins, neurotoxins

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7
Q

Define enterotoxins

A

Enterotoxins - act on intestinal mucosa causing diarrhea

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8
Q

Define cytolytic toxins

A

Cytolytic toxins - kill host cells e.g. Cl. perfringens

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9
Q

Define neurotoxins

A

Neurotoxins - interfere with neural transmission e.g. Botulinum

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10
Q

What are endotoxins?

A

Gram negative bacteria undergo lysis - release lipopolysachharides from the plasma memeberane
e.g. Salmonella

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11
Q

What happens when you ingest a pre-formed toxin?

A

Very short incubation period - show symptoms very quickly.
Toxin does not require person to person spread
Toxin is heat resistant

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12
Q

What is an non-invasive infection? Give examples

A

Non-invasive infection - cells colonize the intestinal lumen and epithelial surface
e.g. E-coli, Cl. Perfingens

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13
Q

What is an invasive infection? Give examples

A

Invasive infection - cells in the intestinal epithelium are invaded and then this infection can pass through to the lamina
e.g. salmonella

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14
Q

What is meant by a D value?

A

Time required to reduce the number of cells by 90%

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15
Q

What is campylobacter caused by?

A

80% caused by raw poultry
Milk
Untreated water

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16
Q

Describe the microbiological features of campylobacter

A 
Campylobacter:
Gram negative
Non-spore forming
Mesophile
Microaerophillic - grows at O2 conc lower than in air
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17
Q

How can camylobacter be reduced in chicken?

A

Freezing it with nitrogen

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18
Q

Describe the infective dose of campylobacter

A

LOW infective does needed

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19
Q

Where is salmonella found?

A

Salmonella is found in the intestinal tract of birds and animals

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20
Q

What are the main sources of salmonella

A

Raw chicken, milk, eggs, meat

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21
Q

What type of organism is salmonella?

A

Zoonotic organism - salmonella is transferred from animals to humans

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22
Q

Describe the microbiological features of salmonella

A 
Salmonella:
Non spore forming
Motile rods
Facultative anaerobe
Can grow at pH's as low as 3.8
4-48 hr incubation period
23
Q

What is the most common salmonella infection?

A

S.Enteritis - a gastrointestinal infection

24
Q

Can salmonella become a systematic disease?

A

Yes, salmonella is a host adaptive serotype.

25
Q

What is the most lethal food bourne illness?

A

Listeria Monocytogenes

26
Q

What is listeria carried by?

A

Humans or animal gut

27
Q

Where is listeria found?

A

Unpasteurised milk, meat (salami and pate), reheated cook to chill meals

28
Q

Describe the microbiological features of listeia

A

Grows at LOW temperatures - grows in fridge
Gram Positive
Non-spore forming
Facultative anaerobe
2.5-45 degree growth range
Destroyed by acidic food, cooking and pasteurization

29
Q

What preservatives is listeria tolerant to?

A

Salt and sodium nitrite

30
Q

What is listeriosis?

A

1-70 day incubation period
High mortality rate (death)
Can have asymptomatic carriers
neonates and pregnant people at risk

31
Q

What percentage of people hospitlaised with listeriosis die?

A

1/3

32
Q

Describe the pathogenicity of E-coli

A

Only a small number of cells needed to cause illness

33
Q

Where is ecoli found?

A

Ecoli is found in the intestinal tract of warm blooded animals

34
Q

What food sources is ecoli found in?

A

E-coli is found in diary and beef

35
Q

How is ecoli spread?

A

Direct contact to animals, faecal to oral route, cross contamination

36
Q

Describe some food outbreaks of e-coli in the past

A

Undercooked beef - 1993, 4 children in USA die

Unpasteurized apple juice

37
Q

Describe the microbiology of e-coli

A 
E-coli:
Non spore forming
Gram negative
Produces verotoxins
Facultative anaerobe
Can grow in pH 4.5 - acid is not an effective control
Mesophile
Resistant to freezing - frozen burgers still contain E-coli
Favours fatty mediums
38
Q

Describe illness caused by E-coli

A 
Mild diarrhea
Haemorrhagic colititis
Uraemia - often young in children
Fatal in young and old
High infectivity
39
Q

What is meant by the z value?

A

The temperature required to reduce number of cells by a further 90%

40
Q

List all spore forming bacteria

A

Spore forming:
Clostridium perfingens
Clostridium botulinum
Bacillus cereus

41
Q

What are the sources of clostridium perfringens?

A

Gastrointestinal tract of mammals
Soil
Dust

42
Q

How is clostridium perfingens transmitted?

A

Contaminated meat and poultry

43
Q

Describe the microbiology of Cl. perfingens

A

Cl. Perfringens:
Spore forming - spores survive low temperature cooking
Gram Positive
Anaerobic
High nutritional requirement - needs 13 amino acids

44
Q

Describe the illness/symtpoms of Cl. perfringnes

A

Large number of cells needed for illness

Cells produce enterotoxins in the intestines

45
Q

What are the sources of Cl. Botulinum?

A

Soil, environment

46
Q

What foods contain Cl. Botulinum?

A

Raw, undercooked or under processed food

Home preservation techniques

47
Q

Describe the growth conditions of Cl. Botulinum Group 1

A

Anaerobic - grows in cans
Cannot grow in refrigerators
Grows at 10-12 degrees
Spores survive severe heat processes - cans need to be sterilized in a botulinum cook at 121 degrees for 3 mins

48
Q

What is a botulinum cook?

A

Heats cans to 121 degrees for 3 mins

49
Q

Describe the growth conditions of Cl. Botulinum Group 2

A

Grows at chilled temperature/ in fridge - 3-5 degrees
Spores are less heat resistant
More likely to grow in chilled vacuum packed foods

50
Q

Where is bacillus cereus found?

A

Bacillus Cereus is found in the environment, soil, sediment and human gut

51
Q

Describe the microbiology of B. Cereus

A 
Spore forming
Gram positive
Motile rods
Facultative anaerobe
28-35 degree optimum temp
52
Q

What toxins are produced by B. Cereus? Can they be destroyed?

A

Pre-formed Emetic toxin - HEAT RESISTANT

Diarrhoeal eneterotoxin - can be destroyed by heat

53
Q

Describe the emetic form of B. Cereus

A

Ingestion of pre-formed heat stable toxin
Vomitiing, Nausea
1-5 hr incubation period
Duration of symptoms - 6-24 hrs

54
Q

What foods do B. Cereus spores grow on?

A

Spores can grow on surfaces because they are very hydrophobic - resist cleaning
Found on dry food - cereals, spices, flour e.g. Vannilla sauce in Norway thickened with cornflour containing spores - heat treatment did not deactivate

Cell biology 1220 (11 decks)

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